[PATCH v9 00/15] large atomic writes for xfs

[PATCH v9 00/15] large atomic writes for xfs

[John Garry]

Currently atomic write support for xfs is limited to writing a single
block as we have no way to guarantee alignment and that the write covers
a single extent.

This series introduces a method to issue atomic writes via a
software-based method.

The software-based method is used as a fallback for when attempting to
issue an atomic write over misaligned or multiple extents.

For xfs, this support is based on reflink CoW support.

The basic idea of this CoW method is to alloc a range in the CoW fork,
write the data, and atomically update the mapping.

Initial mysql performance testing has shown this method to perform ok.
However, there we are only using 16K atomic writes (and 4K block size),
so typically - and thankfully - this software fallback method won't be
used often.

For other FSes which want large atomics writes and don't support CoW, I
think that they can follow the example in [0].

Catherine is currently working on further xfstests for this feature,
which we hope to share soon.

Based on f0447f80aec8 (xfs/next-rc, xfs/for-next) xfs: remove
duplicate Zoned Filesystems sections in admin-guide

[0] https://lore.kernel.org/linux-xfs/20250310183946.932054-1-john.g.garry@oracle.com/

Differences to v8:
- Darrick reworked patch for mount option
- Darrick reworked patch to ignore HW
- Minor changes and cleanups from Darrick
- Rework some commit messages (Christoph)
- Pick up RB tags from Christoph (thanks!)

Differences to v7:
- Add patch for mp hw awu max and min
- Fixed for awu max mount option (Darrick)

Differences to v6:
- log item sizes updates (Darrick)
- rtvol support (Darrick)
- mount option for atomic writes (Darrick)
- Add RB tags from Darrick and Christoph (Thanks!)

Darrick J. Wong (4):
  xfs: add helpers to compute log item overhead
  xfs: add helpers to compute transaction reservation for finishing
    intent items
  xfs: ignore HW which cannot atomic write a single block
  xfs: allow sysadmins to specify a maximum atomic write limit at mount
    time

John Garry (11):
  fs: add atomic write unit max opt to statx
  xfs: rename xfs_inode_can_atomicwrite() ->
    xfs_inode_can_hw_atomic_write()
  xfs: allow block allocator to take an alignment hint
  xfs: refactor xfs_reflink_end_cow_extent()
  xfs: refine atomic write size check in xfs_file_write_iter()
  xfs: add xfs_atomic_write_cow_iomap_begin()
  xfs: add large atomic writes checks in xfs_direct_write_iomap_begin()
  xfs: commit CoW-based atomic writes atomically
  xfs: add xfs_file_dio_write_atomic()
  xfs: add xfs_compute_atomic_write_unit_max()
  xfs: update atomic write limits

 Documentation/admin-guide/xfs.rst |  11 +
 block/bdev.c                      |   3 +-
 fs/ext4/inode.c                   |   2 +-
 fs/stat.c                         |   6 +-
 fs/xfs/libxfs/xfs_bmap.c          |   5 +
 fs/xfs/libxfs/xfs_bmap.h          |   6 +-
 fs/xfs/libxfs/xfs_log_rlimit.c    |   4 +
 fs/xfs/libxfs/xfs_trans_resv.c    | 343 +++++++++++++++++++++++++++---
 fs/xfs/libxfs/xfs_trans_resv.h    |  25 +++
 fs/xfs/xfs_bmap_item.c            |  10 +
 fs/xfs/xfs_bmap_item.h            |   3 +
 fs/xfs/xfs_buf.c                  |  41 +++-
 fs/xfs/xfs_buf.h                  |   3 +-
 fs/xfs/xfs_buf_item.c             |  19 ++
 fs/xfs/xfs_buf_item.h             |   3 +
 fs/xfs/xfs_extfree_item.c         |  10 +
 fs/xfs/xfs_extfree_item.h         |   3 +
 fs/xfs/xfs_file.c                 |  87 +++++++-
 fs/xfs/xfs_inode.h                |  14 +-
 fs/xfs/xfs_iomap.c                | 190 ++++++++++++++++-
 fs/xfs/xfs_iomap.h                |   1 +
 fs/xfs/xfs_iops.c                 |  76 ++++++-
 fs/xfs/xfs_iops.h                 |   3 +
 fs/xfs/xfs_log_cil.c              |   4 +-
 fs/xfs/xfs_log_priv.h             |  13 ++
 fs/xfs/xfs_mount.c                | 166 +++++++++++++++
 fs/xfs/xfs_mount.h                |  17 ++
 fs/xfs/xfs_refcount_item.c        |  10 +
 fs/xfs/xfs_refcount_item.h        |   3 +
 fs/xfs/xfs_reflink.c              | 146 ++++++++++---
 fs/xfs/xfs_reflink.h              |   6 +
 fs/xfs/xfs_rmap_item.c            |  10 +
 fs/xfs/xfs_rmap_item.h            |   3 +
 fs/xfs/xfs_super.c                |  58 ++++-
 fs/xfs/xfs_trace.h                | 115 ++++++++++
 include/linux/fs.h                |   3 +-
 include/linux/stat.h              |   1 +
 include/uapi/linux/stat.h         |   8 +-
 38 files changed, 1322 insertions(+), 109 deletions(-)

-- 
2.31.1

[PATCH v9 01/15] fs: add atomic write unit max opt to statx

[John Garry]

XFS will be able to support large atomic writes (atomic write > 1x block)
in future. This will be achieved by using different operating methods,
depending on the size of the write.

Specifically a new method of operation based in FS atomic extent remapping
will be supported in addition to the current HW offload-based method.

The FS method will generally be appreciably slower performing than the
HW-offload method. However the FS method will be typically able to
contribute to achieving a larger atomic write unit max limit.

XFS will support a hybrid mode, where HW offload method will be used when
possible, i.e. HW offload is used when the length of the write is
supported, and for other times FS-based atomic writes will be used.

As such, there is an atomic write length at which the user may experience
appreciably slower performance.

Advertise this limit in a new statx field, stx_atomic_write_unit_max_opt.

When zero, it means that there is no such performance boundary.

Masks STATX{_ATTR}_WRITE_ATOMIC can be used to get this new field. This is
ok for older kernels which don't support this new field, as they would
report 0 in this field (from zeroing in cp_statx()) already. Furthermore
those older kernels don't support large atomic writes - apart from block
fops, but there would be consistent performance there for atomic writes
in range [unit min, unit max].

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 block/bdev.c              | 3 ++-
 fs/ext4/inode.c           | 2 +-
 fs/stat.c                 | 6 +++++-
 fs/xfs/xfs_iops.c         | 2 +-
 include/linux/fs.h        | 3 ++-
 include/linux/stat.h      | 1 +
 include/uapi/linux/stat.h | 8 ++++++--
 7 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 4844d1e27b6f..b4afc1763e8e 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -1301,7 +1301,8 @@ void bdev_statx(struct path *path, struct kstat *stat,
 
 		generic_fill_statx_atomic_writes(stat,
 			queue_atomic_write_unit_min_bytes(bd_queue),
-			queue_atomic_write_unit_max_bytes(bd_queue));
+			queue_atomic_write_unit_max_bytes(bd_queue),
+			0);
 	}
 
 	stat->blksize = bdev_io_min(bdev);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 94c7d2d828a6..cdf01e60fa6d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5692,7 +5692,7 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
 			awu_max = sbi->s_awu_max;
 		}
 
-		generic_fill_statx_atomic_writes(stat, awu_min, awu_max);
+		generic_fill_statx_atomic_writes(stat, awu_min, awu_max, 0);
 	}
 
 	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
diff --git a/fs/stat.c b/fs/stat.c
index f13308bfdc98..c41855f62d22 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -136,13 +136,15 @@ EXPORT_SYMBOL(generic_fill_statx_attr);
  * @stat:	Where to fill in the attribute flags
  * @unit_min:	Minimum supported atomic write length in bytes
  * @unit_max:	Maximum supported atomic write length in bytes
+ * @unit_max_opt: Optimised maximum supported atomic write length in bytes
  *
  * Fill in the STATX{_ATTR}_WRITE_ATOMIC flags in the kstat structure from
  * atomic write unit_min and unit_max values.
  */
 void generic_fill_statx_atomic_writes(struct kstat *stat,
 				      unsigned int unit_min,
-				      unsigned int unit_max)
+				      unsigned int unit_max,
+				      unsigned int unit_max_opt)
 {
 	/* Confirm that the request type is known */
 	stat->result_mask |= STATX_WRITE_ATOMIC;
@@ -153,6 +155,7 @@ void generic_fill_statx_atomic_writes(struct kstat *stat,
 	if (unit_min) {
 		stat->atomic_write_unit_min = unit_min;
 		stat->atomic_write_unit_max = unit_max;
+		stat->atomic_write_unit_max_opt = unit_max_opt;
 		/* Initially only allow 1x segment */
 		stat->atomic_write_segments_max = 1;
 
@@ -732,6 +735,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
 	tmp.stx_atomic_write_unit_min = stat->atomic_write_unit_min;
 	tmp.stx_atomic_write_unit_max = stat->atomic_write_unit_max;
 	tmp.stx_atomic_write_segments_max = stat->atomic_write_segments_max;
+	tmp.stx_atomic_write_unit_max_opt = stat->atomic_write_unit_max_opt;
 
 	return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;
 }
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 756bd3ca8e00..f0e5d83195df 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -610,7 +610,7 @@ xfs_report_atomic_write(
 
 	if (xfs_inode_can_atomicwrite(ip))
 		unit_min = unit_max = ip->i_mount->m_sb.sb_blocksize;
-	generic_fill_statx_atomic_writes(stat, unit_min, unit_max);
+	generic_fill_statx_atomic_writes(stat, unit_min, unit_max, 0);
 }
 
 STATIC int
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 016b0fe1536e..7b19d8f99aff 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3475,7 +3475,8 @@ void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *);
 void generic_fill_statx_attr(struct inode *inode, struct kstat *stat);
 void generic_fill_statx_atomic_writes(struct kstat *stat,
 				      unsigned int unit_min,
-				      unsigned int unit_max);
+				      unsigned int unit_max,
+				      unsigned int unit_max_opt);
 extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);
 extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int);
 void __inode_add_bytes(struct inode *inode, loff_t bytes);
diff --git a/include/linux/stat.h b/include/linux/stat.h
index be7496a6a0dd..e3d00e7bb26d 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -57,6 +57,7 @@ struct kstat {
 	u32		dio_read_offset_align;
 	u32		atomic_write_unit_min;
 	u32		atomic_write_unit_max;
+	u32		atomic_write_unit_max_opt;
 	u32		atomic_write_segments_max;
 };
 
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index f78ee3670dd5..1686861aae20 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -182,8 +182,12 @@ struct statx {
 	/* File offset alignment for direct I/O reads */
 	__u32	stx_dio_read_offset_align;
 
-	/* 0xb8 */
-	__u64	__spare3[9];	/* Spare space for future expansion */
+	/* Optimised max atomic write unit in bytes */
+	__u32	stx_atomic_write_unit_max_opt;
+	__u32	__spare2[1];
+
+	/* 0xc0 */
+	__u64	__spare3[8];	/* Spare space for future expansion */
 
 	/* 0x100 */
 };
-- 
2.31.1

[PATCH v9 02/15] xfs: add helpers to compute log item overhead

[John Garry]

From: "Darrick J. Wong" <djwong@kernel.org>

Add selected helpers to estimate the transaction reservation required to
write various log intent and buffer items to the log.  These helpers
will be used by the online repair code for more precise estimations of
how much work can be done in a single transaction.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/xfs_bmap_item.c     | 10 ++++++++++
 fs/xfs/xfs_bmap_item.h     |  3 +++
 fs/xfs/xfs_buf_item.c      | 19 +++++++++++++++++++
 fs/xfs/xfs_buf_item.h      |  3 +++
 fs/xfs/xfs_extfree_item.c  | 10 ++++++++++
 fs/xfs/xfs_extfree_item.h  |  3 +++
 fs/xfs/xfs_log_cil.c       |  4 +---
 fs/xfs/xfs_log_priv.h      | 13 +++++++++++++
 fs/xfs/xfs_refcount_item.c | 10 ++++++++++
 fs/xfs/xfs_refcount_item.h |  3 +++
 fs/xfs/xfs_rmap_item.c     | 10 ++++++++++
 fs/xfs/xfs_rmap_item.h     |  3 +++
 12 files changed, 88 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
index 3d52e9d7ad57..646c515ee355 100644
--- a/fs/xfs/xfs_bmap_item.c
+++ b/fs/xfs/xfs_bmap_item.c
@@ -77,6 +77,11 @@ xfs_bui_item_size(
 	*nbytes += xfs_bui_log_format_sizeof(buip->bui_format.bui_nextents);
 }
 
+unsigned int xfs_bui_log_space(unsigned int nr)
+{
+	return xlog_item_space(1, xfs_bui_log_format_sizeof(nr));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given bui log item. We use only 1 iovec, and we point that
@@ -168,6 +173,11 @@ xfs_bud_item_size(
 	*nbytes += sizeof(struct xfs_bud_log_format);
 }
 
+unsigned int xfs_bud_log_space(void)
+{
+	return xlog_item_space(1, sizeof(struct xfs_bud_log_format));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given bud log item. We use only 1 iovec, and we point that
diff --git a/fs/xfs/xfs_bmap_item.h b/fs/xfs/xfs_bmap_item.h
index 6fee6a508343..b42fee06899d 100644
--- a/fs/xfs/xfs_bmap_item.h
+++ b/fs/xfs/xfs_bmap_item.h
@@ -72,4 +72,7 @@ struct xfs_bmap_intent;
 
 void xfs_bmap_defer_add(struct xfs_trans *tp, struct xfs_bmap_intent *bi);
 
+unsigned int xfs_bui_log_space(unsigned int nr);
+unsigned int xfs_bud_log_space(void);
+
 #endif	/* __XFS_BMAP_ITEM_H__ */
diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 19eb0b7a3e58..90139e0f3271 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -103,6 +103,25 @@ xfs_buf_item_size_segment(
 	return;
 }
 
+/*
+ * Compute the worst case log item overhead for an invalidated buffer with the
+ * given map count and block size.
+ */
+unsigned int
+xfs_buf_inval_log_space(
+	unsigned int	map_count,
+	unsigned int	blocksize)
+{
+	unsigned int	chunks = DIV_ROUND_UP(blocksize, XFS_BLF_CHUNK);
+	unsigned int	bitmap_size = DIV_ROUND_UP(chunks, NBWORD);
+	unsigned int	ret =
+		offsetof(struct xfs_buf_log_format, blf_data_map) +
+			(bitmap_size * sizeof_field(struct xfs_buf_log_format,
+						    blf_data_map[0]));
+
+	return ret * map_count;
+}
+
 /*
  * Return the number of log iovecs and space needed to log the given buf log
  * item.
diff --git a/fs/xfs/xfs_buf_item.h b/fs/xfs/xfs_buf_item.h
index 8cde85259a58..e10e324cd245 100644
--- a/fs/xfs/xfs_buf_item.h
+++ b/fs/xfs/xfs_buf_item.h
@@ -64,6 +64,9 @@ static inline void xfs_buf_dquot_iodone(struct xfs_buf *bp)
 void	xfs_buf_iodone(struct xfs_buf *);
 bool	xfs_buf_log_check_iovec(struct xfs_log_iovec *iovec);
 
+unsigned int xfs_buf_inval_log_space(unsigned int map_count,
+		unsigned int blocksize);
+
 extern struct kmem_cache	*xfs_buf_item_cache;
 
 #endif	/* __XFS_BUF_ITEM_H__ */
diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
index 777438b853da..d574f5f639fa 100644
--- a/fs/xfs/xfs_extfree_item.c
+++ b/fs/xfs/xfs_extfree_item.c
@@ -83,6 +83,11 @@ xfs_efi_item_size(
 	*nbytes += xfs_efi_log_format_sizeof(efip->efi_format.efi_nextents);
 }
 
+unsigned int xfs_efi_log_space(unsigned int nr)
+{
+	return xlog_item_space(1, xfs_efi_log_format_sizeof(nr));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given efi log item. We use only 1 iovec, and we point that
@@ -254,6 +259,11 @@ xfs_efd_item_size(
 	*nbytes += xfs_efd_log_format_sizeof(efdp->efd_format.efd_nextents);
 }
 
+unsigned int xfs_efd_log_space(unsigned int nr)
+{
+	return xlog_item_space(1, xfs_efd_log_format_sizeof(nr));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given efd log item. We use only 1 iovec, and we point that
diff --git a/fs/xfs/xfs_extfree_item.h b/fs/xfs/xfs_extfree_item.h
index 41b7c4306079..c8402040410b 100644
--- a/fs/xfs/xfs_extfree_item.h
+++ b/fs/xfs/xfs_extfree_item.h
@@ -94,4 +94,7 @@ void xfs_extent_free_defer_add(struct xfs_trans *tp,
 		struct xfs_extent_free_item *xefi,
 		struct xfs_defer_pending **dfpp);
 
+unsigned int xfs_efi_log_space(unsigned int nr);
+unsigned int xfs_efd_log_space(unsigned int nr);
+
 #endif	/* __XFS_EXTFREE_ITEM_H__ */
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 1ca406ec1b40..f66d2d430e4f 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -309,9 +309,7 @@ xlog_cil_alloc_shadow_bufs(
 		 * Then round nbytes up to 64-bit alignment so that the initial
 		 * buffer alignment is easy to calculate and verify.
 		 */
-		nbytes += niovecs *
-			(sizeof(uint64_t) + sizeof(struct xlog_op_header));
-		nbytes = round_up(nbytes, sizeof(uint64_t));
+		nbytes = xlog_item_space(niovecs, nbytes);
 
 		/*
 		 * The data buffer needs to start 64-bit aligned, so round up
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index f3d78869e5e5..39a102cc1b43 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -698,4 +698,17 @@ xlog_kvmalloc(
 	return p;
 }
 
+/*
+ * Given a count of iovecs and space for a log item, compute the space we need
+ * in the log to store that data plus the log headers.
+ */
+static inline unsigned int
+xlog_item_space(
+	unsigned int	niovecs,
+	unsigned int	nbytes)
+{
+	nbytes += niovecs * (sizeof(uint64_t) + sizeof(struct xlog_op_header));
+	return round_up(nbytes, sizeof(uint64_t));
+}
+
 #endif	/* __XFS_LOG_PRIV_H__ */
diff --git a/fs/xfs/xfs_refcount_item.c b/fs/xfs/xfs_refcount_item.c
index fe2d7aab8554..076501123d89 100644
--- a/fs/xfs/xfs_refcount_item.c
+++ b/fs/xfs/xfs_refcount_item.c
@@ -78,6 +78,11 @@ xfs_cui_item_size(
 	*nbytes += xfs_cui_log_format_sizeof(cuip->cui_format.cui_nextents);
 }
 
+unsigned int xfs_cui_log_space(unsigned int nr)
+{
+	return xlog_item_space(1, xfs_cui_log_format_sizeof(nr));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given cui log item. We use only 1 iovec, and we point that
@@ -179,6 +184,11 @@ xfs_cud_item_size(
 	*nbytes += sizeof(struct xfs_cud_log_format);
 }
 
+unsigned int xfs_cud_log_space(void)
+{
+	return xlog_item_space(1, sizeof(struct xfs_cud_log_format));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given cud log item. We use only 1 iovec, and we point that
diff --git a/fs/xfs/xfs_refcount_item.h b/fs/xfs/xfs_refcount_item.h
index bfee8f30c63c..0fc3f493342b 100644
--- a/fs/xfs/xfs_refcount_item.h
+++ b/fs/xfs/xfs_refcount_item.h
@@ -76,4 +76,7 @@ struct xfs_refcount_intent;
 void xfs_refcount_defer_add(struct xfs_trans *tp,
 		struct xfs_refcount_intent *ri);
 
+unsigned int xfs_cui_log_space(unsigned int nr);
+unsigned int xfs_cud_log_space(void);
+
 #endif	/* __XFS_REFCOUNT_ITEM_H__ */
diff --git a/fs/xfs/xfs_rmap_item.c b/fs/xfs/xfs_rmap_item.c
index 89decffe76c8..c99700318ec2 100644
--- a/fs/xfs/xfs_rmap_item.c
+++ b/fs/xfs/xfs_rmap_item.c
@@ -77,6 +77,11 @@ xfs_rui_item_size(
 	*nbytes += xfs_rui_log_format_sizeof(ruip->rui_format.rui_nextents);
 }
 
+unsigned int xfs_rui_log_space(unsigned int nr)
+{
+	return xlog_item_space(1, xfs_rui_log_format_sizeof(nr));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given rui log item. We use only 1 iovec, and we point that
@@ -180,6 +185,11 @@ xfs_rud_item_size(
 	*nbytes += sizeof(struct xfs_rud_log_format);
 }
 
+unsigned int xfs_rud_log_space(void)
+{
+	return xlog_item_space(1, sizeof(struct xfs_rud_log_format));
+}
+
 /*
  * This is called to fill in the vector of log iovecs for the
  * given rud log item. We use only 1 iovec, and we point that
diff --git a/fs/xfs/xfs_rmap_item.h b/fs/xfs/xfs_rmap_item.h
index 40d331555675..3a99f0117f2d 100644
--- a/fs/xfs/xfs_rmap_item.h
+++ b/fs/xfs/xfs_rmap_item.h
@@ -75,4 +75,7 @@ struct xfs_rmap_intent;
 
 void xfs_rmap_defer_add(struct xfs_trans *tp, struct xfs_rmap_intent *ri);
 
+unsigned int xfs_rui_log_space(unsigned int nr);
+unsigned int xfs_rud_log_space(void);
+
 #endif	/* __XFS_RMAP_ITEM_H__ */
-- 
2.31.1

[PATCH v9 03/15] xfs: add helpers to compute transaction reservation for finishing intent items

[John Garry]

From: "Darrick J. Wong" <djwong@kernel.org>

In the transaction reservation code, hoist the logic that computes the
reservation needed to finish one log intent item into separate helper
functions.  These will be used in subsequent patches to estimate the
number of blocks that an online repair can commit to reaping in the same
transaction as the change committing the new data structure.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/libxfs/xfs_trans_resv.c | 165 ++++++++++++++++++++++++++-------
 fs/xfs/libxfs/xfs_trans_resv.h |  18 ++++
 2 files changed, 152 insertions(+), 31 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index 13d00c7166e1..580d00ae2857 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -263,6 +263,42 @@ xfs_rtalloc_block_count(
  * register overflow from temporaries in the calculations.
  */
 
+/*
+ * Finishing a data device refcount updates (t1):
+ *    the agfs of the ags containing the blocks: nr_ops * sector size
+ *    the refcount btrees: nr_ops * 1 trees * (2 * max depth - 1) * block size
+ */
+inline unsigned int
+xfs_calc_finish_cui_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr_ops)
+{
+	if (!xfs_has_reflink(mp))
+		return 0;
+
+	return xfs_calc_buf_res(nr_ops, mp->m_sb.sb_sectsize) +
+	       xfs_calc_buf_res(xfs_refcountbt_block_count(mp, nr_ops),
+			       mp->m_sb.sb_blocksize);
+}
+
+/*
+ * Realtime refcount updates (t2);
+ *    the rt refcount inode
+ *    the rtrefcount btrees: nr_ops * 1 trees * (2 * max depth - 1) * block size
+ */
+inline unsigned int
+xfs_calc_finish_rt_cui_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr_ops)
+{
+	if (!xfs_has_rtreflink(mp))
+		return 0;
+
+	return xfs_calc_inode_res(mp, 1) +
+	       xfs_calc_buf_res(xfs_rtrefcountbt_block_count(mp, nr_ops),
+				     mp->m_sb.sb_blocksize);
+}
+
 /*
  * Compute the log reservation required to handle the refcount update
  * transaction.  Refcount updates are always done via deferred log items.
@@ -280,19 +316,10 @@ xfs_calc_refcountbt_reservation(
 	struct xfs_mount	*mp,
 	unsigned int		nr_ops)
 {
-	unsigned int		blksz = XFS_FSB_TO_B(mp, 1);
-	unsigned int		t1, t2 = 0;
+	unsigned int		t1, t2;
 
-	if (!xfs_has_reflink(mp))
-		return 0;
-
-	t1 = xfs_calc_buf_res(nr_ops, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_refcountbt_block_count(mp, nr_ops), blksz);
-
-	if (xfs_has_realtime(mp))
-		t2 = xfs_calc_inode_res(mp, 1) +
-		     xfs_calc_buf_res(xfs_rtrefcountbt_block_count(mp, nr_ops),
-				     blksz);
+	t1 = xfs_calc_finish_cui_reservation(mp, nr_ops);
+	t2 = xfs_calc_finish_rt_cui_reservation(mp, nr_ops);
 
 	return max(t1, t2);
 }
@@ -379,6 +406,96 @@ xfs_calc_write_reservation_minlogsize(
 	return xfs_calc_write_reservation(mp, true);
 }
 
+/*
+ * Finishing an EFI can free the blocks and bmap blocks (t2):
+ *    the agf for each of the ags: nr * sector size
+ *    the agfl for each of the ags: nr * sector size
+ *    the super block to reflect the freed blocks: sector size
+ *    worst case split in allocation btrees per extent assuming nr extents:
+ *		nr exts * 2 trees * (2 * max depth - 1) * block size
+ */
+inline unsigned int
+xfs_calc_finish_efi_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr)
+{
+	return xfs_calc_buf_res((2 * nr) + 1, mp->m_sb.sb_sectsize) +
+	       xfs_calc_buf_res(xfs_allocfree_block_count(mp, nr),
+			       mp->m_sb.sb_blocksize);
+}
+
+/*
+ * Or, if it's a realtime file (t3):
+ *    the agf for each of the ags: 2 * sector size
+ *    the agfl for each of the ags: 2 * sector size
+ *    the super block to reflect the freed blocks: sector size
+ *    the realtime bitmap:
+ *		2 exts * ((XFS_BMBT_MAX_EXTLEN / rtextsize) / NBBY) bytes
+ *    the realtime summary: 2 exts * 1 block
+ *    worst case split in allocation btrees per extent assuming 2 extents:
+ *		2 exts * 2 trees * (2 * max depth - 1) * block size
+ */
+inline unsigned int
+xfs_calc_finish_rt_efi_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr)
+{
+	if (!xfs_has_realtime(mp))
+		return 0;
+
+	return xfs_calc_buf_res((2 * nr) + 1, mp->m_sb.sb_sectsize) +
+	       xfs_calc_buf_res(xfs_rtalloc_block_count(mp, nr),
+			       mp->m_sb.sb_blocksize) +
+	       xfs_calc_buf_res(xfs_allocfree_block_count(mp, nr),
+			       mp->m_sb.sb_blocksize);
+}
+
+/*
+ * Finishing an RUI is the same as an EFI.  We can split the rmap btree twice
+ * on each end of the record, and that can cause the AGFL to be refilled or
+ * emptied out.
+ */
+inline unsigned int
+xfs_calc_finish_rui_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr)
+{
+	if (!xfs_has_rmapbt(mp))
+		return 0;
+	return xfs_calc_finish_efi_reservation(mp, nr);
+}
+
+/*
+ * Finishing an RUI is the same as an EFI.  We can split the rmap btree twice
+ * on each end of the record, and that can cause the AGFL to be refilled or
+ * emptied out.
+ */
+inline unsigned int
+xfs_calc_finish_rt_rui_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr)
+{
+	if (!xfs_has_rtrmapbt(mp))
+		return 0;
+	return xfs_calc_finish_rt_efi_reservation(mp, nr);
+}
+
+/*
+ * In finishing a BUI, we can modify:
+ *    the inode being truncated: inode size
+ *    dquots
+ *    the inode's bmap btree: (max depth + 1) * block size
+ */
+inline unsigned int
+xfs_calc_finish_bui_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr)
+{
+	return xfs_calc_inode_res(mp, 1) + XFS_DQUOT_LOGRES +
+	       xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1,
+			       mp->m_sb.sb_blocksize);
+}
+
 /*
  * In truncating a file we free up to two extents at once.  We can modify (t1):
  *    the inode being truncated: inode size
@@ -411,16 +528,8 @@ xfs_calc_itruncate_reservation(
 	t1 = xfs_calc_inode_res(mp, 1) +
 	     xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1, blksz);
 
-	t2 = xfs_calc_buf_res(9, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 4), blksz);
-
-	if (xfs_has_realtime(mp)) {
-		t3 = xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) +
-		     xfs_calc_buf_res(xfs_rtalloc_block_count(mp, 2), blksz) +
-		     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 2), blksz);
-	} else {
-		t3 = 0;
-	}
+	t2 = xfs_calc_finish_efi_reservation(mp, 4);
+	t3 = xfs_calc_finish_rt_efi_reservation(mp, 2);
 
 	/*
 	 * In the early days of reflink, we included enough reservation to log
@@ -501,9 +610,7 @@ xfs_calc_rename_reservation(
 	     xfs_calc_buf_res(2 * XFS_DIROP_LOG_COUNT(mp),
 			XFS_FSB_TO_B(mp, 1));
 
-	t2 = xfs_calc_buf_res(7, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 3),
-			XFS_FSB_TO_B(mp, 1));
+	t2 = xfs_calc_finish_efi_reservation(mp, 3);
 
 	if (xfs_has_parent(mp)) {
 		unsigned int	rename_overhead, exchange_overhead;
@@ -611,9 +718,7 @@ xfs_calc_link_reservation(
 	overhead += xfs_calc_iunlink_remove_reservation(mp);
 	t1 = xfs_calc_inode_res(mp, 2) +
 	     xfs_calc_buf_res(XFS_DIROP_LOG_COUNT(mp), XFS_FSB_TO_B(mp, 1));
-	t2 = xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1),
-			      XFS_FSB_TO_B(mp, 1));
+	t2 = xfs_calc_finish_efi_reservation(mp, 1);
 
 	if (xfs_has_parent(mp)) {
 		t3 = resp->tr_attrsetm.tr_logres;
@@ -676,9 +781,7 @@ xfs_calc_remove_reservation(
 
 	t1 = xfs_calc_inode_res(mp, 2) +
 	     xfs_calc_buf_res(XFS_DIROP_LOG_COUNT(mp), XFS_FSB_TO_B(mp, 1));
-	t2 = xfs_calc_buf_res(4, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 2),
-			      XFS_FSB_TO_B(mp, 1));
+	t2 = xfs_calc_finish_efi_reservation(mp, 2);
 
 	if (xfs_has_parent(mp)) {
 		t3 = resp->tr_attrrm.tr_logres;
diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
index 0554b9d775d2..d9d0032cbbc5 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.h
+++ b/fs/xfs/libxfs/xfs_trans_resv.h
@@ -98,6 +98,24 @@ struct xfs_trans_resv {
 void xfs_trans_resv_calc(struct xfs_mount *mp, struct xfs_trans_resv *resp);
 uint xfs_allocfree_block_count(struct xfs_mount *mp, uint num_ops);
 
+unsigned int xfs_calc_finish_bui_reservation(struct xfs_mount *mp,
+		unsigned int nr_ops);
+
+unsigned int xfs_calc_finish_efi_reservation(struct xfs_mount *mp,
+		unsigned int nr_ops);
+unsigned int xfs_calc_finish_rt_efi_reservation(struct xfs_mount *mp,
+		unsigned int nr_ops);
+
+unsigned int xfs_calc_finish_rui_reservation(struct xfs_mount *mp,
+		unsigned int nr_ops);
+unsigned int xfs_calc_finish_rt_rui_reservation(struct xfs_mount *mp,
+		unsigned int nr_ops);
+
+unsigned int xfs_calc_finish_cui_reservation(struct xfs_mount *mp,
+		unsigned int nr_ops);
+unsigned int xfs_calc_finish_rt_cui_reservation(struct xfs_mount *mp,
+		unsigned int nr_ops);
+
 unsigned int xfs_calc_itruncate_reservation_minlogsize(struct xfs_mount *mp);
 unsigned int xfs_calc_write_reservation_minlogsize(struct xfs_mount *mp);
 unsigned int xfs_calc_qm_dqalloc_reservation_minlogsize(struct xfs_mount *mp);
-- 
2.31.1

[PATCH v9 04/15] xfs: rename xfs_inode_can_atomicwrite() -> xfs_inode_can_hw_atomic_write()

[John Garry]

In future we will want to be able to check if specifically HW offload-based
atomic writes are possible, so rename xfs_inode_can_atomicwrite() ->
xfs_inode_can_hw_atomicwrite().

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: add an underscore to be consistent with everything else]
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/xfs_file.c  | 2 +-
 fs/xfs/xfs_inode.h | 2 +-
 fs/xfs/xfs_iops.c  | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 84f08c976ac4..55bdae44e42a 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1488,7 +1488,7 @@ xfs_file_open(
 	if (xfs_is_shutdown(XFS_M(inode->i_sb)))
 		return -EIO;
 	file->f_mode |= FMODE_NOWAIT | FMODE_CAN_ODIRECT;
-	if (xfs_inode_can_atomicwrite(XFS_I(inode)))
+	if (xfs_inode_can_hw_atomic_write(XFS_I(inode)))
 		file->f_mode |= FMODE_CAN_ATOMIC_WRITE;
 	return generic_file_open(inode, file);
 }
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index eae0159983ca..bdbbff0d8d99 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -357,7 +357,7 @@ static inline bool xfs_inode_has_bigrtalloc(const struct xfs_inode *ip)
 		(ip)->i_mount->m_rtdev_targp : (ip)->i_mount->m_ddev_targp)
 
 static inline bool
-xfs_inode_can_atomicwrite(
+xfs_inode_can_hw_atomic_write(
 	struct xfs_inode	*ip)
 {
 	struct xfs_mount	*mp = ip->i_mount;
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index f0e5d83195df..22432c300fd7 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -608,7 +608,7 @@ xfs_report_atomic_write(
 {
 	unsigned int		unit_min = 0, unit_max = 0;
 
-	if (xfs_inode_can_atomicwrite(ip))
+	if (xfs_inode_can_hw_atomic_write(ip))
 		unit_min = unit_max = ip->i_mount->m_sb.sb_blocksize;
 	generic_fill_statx_atomic_writes(stat, unit_min, unit_max, 0);
 }
-- 
2.31.1

[PATCH v9 05/15] xfs: ignore HW which cannot atomic write a single block

[John Garry]

From: "Darrick J. Wong" <djwong@kernel.org>

Currently only HW which can write at least 1x block is supported.

For supporting atomic writes > 1x block, a CoW-based method will also be
used and this will not be resticted to using HW which can write >= 1x
block.

However for deciding if HW-based atomic writes can be used, we need to
start adding checks for write length < HW min, which complicates the
code.  Indeed, a statx field similar to unit_max_opt should also be
added for this minimum, which is undesirable.

HW which can only write > 1x blocks would be uncommon and quite weird,
so let's just not support it.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/xfs_buf.c   | 41 ++++++++++++++++++++++++++++++++++-------
 fs/xfs/xfs_buf.h   |  3 ++-
 fs/xfs/xfs_inode.h | 14 ++------------
 fs/xfs/xfs_mount.c |  7 +++++++
 4 files changed, 45 insertions(+), 20 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 1a2b3f06fa71..f165446a082c 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1772,6 +1772,40 @@ xfs_init_buftarg(
 	return -ENOMEM;
 }
 
+/*
+ * Configure this buffer target for hardware-assisted atomic writes if the
+ * underlying block device supports is congruent with the filesystem geometry.
+ */
+void
+xfs_buftarg_config_atomic_writes(
+	struct xfs_buftarg	*btp)
+{
+	struct xfs_mount	*mp = btp->bt_mount;
+	unsigned int		min_bytes, max_bytes;
+
+	ASSERT(btp->bt_bdev != NULL);
+
+	if (!bdev_can_atomic_write(btp->bt_bdev))
+		return;
+
+	min_bytes = bdev_atomic_write_unit_min_bytes(btp->bt_bdev);
+	max_bytes = bdev_atomic_write_unit_max_bytes(btp->bt_bdev);
+
+	/*
+	 * Ignore atomic write geometry that is nonsense or doesn't even cover
+	 * a single fsblock.
+	 */
+	if (min_bytes > max_bytes ||
+	    min_bytes > mp->m_sb.sb_blocksize ||
+	    max_bytes < mp->m_sb.sb_blocksize) {
+		min_bytes = 0;
+		max_bytes = 0;
+	}
+
+	btp->bt_bdev_awu_min = min_bytes;
+	btp->bt_bdev_awu_max = max_bytes;
+}
+
 struct xfs_buftarg *
 xfs_alloc_buftarg(
 	struct xfs_mount	*mp,
@@ -1792,13 +1826,6 @@ xfs_alloc_buftarg(
 	btp->bt_daxdev = fs_dax_get_by_bdev(btp->bt_bdev, &btp->bt_dax_part_off,
 					    mp, ops);
 
-	if (bdev_can_atomic_write(btp->bt_bdev)) {
-		btp->bt_bdev_awu_min = bdev_atomic_write_unit_min_bytes(
-						btp->bt_bdev);
-		btp->bt_bdev_awu_max = bdev_atomic_write_unit_max_bytes(
-						btp->bt_bdev);
-	}
-
 	/*
 	 * When allocating the buftargs we have not yet read the super block and
 	 * thus don't know the file system sector size yet.
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index d0b065a9a9f0..6f691779887f 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -112,7 +112,7 @@ struct xfs_buftarg {
 	struct percpu_counter	bt_readahead_count;
 	struct ratelimit_state	bt_ioerror_rl;
 
-	/* Atomic write unit values */
+	/* Atomic write unit values, bytes */
 	unsigned int		bt_bdev_awu_min;
 	unsigned int		bt_bdev_awu_max;
 
@@ -375,6 +375,7 @@ extern void xfs_free_buftarg(struct xfs_buftarg *);
 extern void xfs_buftarg_wait(struct xfs_buftarg *);
 extern void xfs_buftarg_drain(struct xfs_buftarg *);
 extern int xfs_setsize_buftarg(struct xfs_buftarg *, unsigned int);
+void xfs_buftarg_config_atomic_writes(struct xfs_buftarg *btp);
 
 #define xfs_getsize_buftarg(buftarg)	block_size((buftarg)->bt_bdev)
 #define xfs_readonly_buftarg(buftarg)	bdev_read_only((buftarg)->bt_bdev)
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index bdbbff0d8d99..d7e2b902ef5c 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -356,19 +356,9 @@ static inline bool xfs_inode_has_bigrtalloc(const struct xfs_inode *ip)
 	(XFS_IS_REALTIME_INODE(ip) ? \
 		(ip)->i_mount->m_rtdev_targp : (ip)->i_mount->m_ddev_targp)
 
-static inline bool
-xfs_inode_can_hw_atomic_write(
-	struct xfs_inode	*ip)
+static inline bool xfs_inode_can_hw_atomic_write(const struct xfs_inode *ip)
 {
-	struct xfs_mount	*mp = ip->i_mount;
-	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
-
-	if (mp->m_sb.sb_blocksize < target->bt_bdev_awu_min)
-		return false;
-	if (mp->m_sb.sb_blocksize > target->bt_bdev_awu_max)
-		return false;
-
-	return true;
+	return xfs_inode_buftarg(ip)->bt_bdev_awu_max > 0;
 }
 
 /*
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 00b53f479ece..1082b322e6d6 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1082,6 +1082,13 @@ xfs_mountfs(
 		xfs_zone_gc_start(mp);
 	}
 
+	/* Configure hardware atomic write geometry */
+	xfs_buftarg_config_atomic_writes(mp->m_ddev_targp);
+	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
+		xfs_buftarg_config_atomic_writes(mp->m_logdev_targp);
+	if (mp->m_rtdev_targp && mp->m_rtdev_targp != mp->m_ddev_targp)
+		xfs_buftarg_config_atomic_writes(mp->m_rtdev_targp);
+
 	return 0;
 
  out_agresv:
-- 
2.31.1

Re: [PATCH v9 05/15] xfs: ignore HW which cannot atomic write a single block

[Christoph Hellwig]

On Fri, Apr 25, 2025 at 04:44:54PM +0000, John Garry wrote:
> +	/* Configure hardware atomic write geometry */
> +	xfs_buftarg_config_atomic_writes(mp->m_ddev_targp);
> +	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
> +		xfs_buftarg_config_atomic_writes(mp->m_logdev_targp);
> +	if (mp->m_rtdev_targp && mp->m_rtdev_targp != mp->m_ddev_targp)
> +		xfs_buftarg_config_atomic_writes(mp->m_rtdev_targp);

So this can't be merged into xfs_setsize_buftarg as suggeted last round
instead of needing yet another per-device call into the buftarg code?

Re: [PATCH v9 05/15] xfs: ignore HW which cannot atomic write a single block

[Darrick J. Wong]

On Tue, Apr 29, 2025 at 02:21:05PM +0200, Christoph Hellwig wrote:
> On Fri, Apr 25, 2025 at 04:44:54PM +0000, John Garry wrote:
> > +	/* Configure hardware atomic write geometry */
> > +	xfs_buftarg_config_atomic_writes(mp->m_ddev_targp);
> > +	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
> > +		xfs_buftarg_config_atomic_writes(mp->m_logdev_targp);
> > +	if (mp->m_rtdev_targp && mp->m_rtdev_targp != mp->m_ddev_targp)
> > +		xfs_buftarg_config_atomic_writes(mp->m_rtdev_targp);
> 
> So this can't be merged into xfs_setsize_buftarg as suggeted last round
> instead of needing yet another per-device call into the buftarg code?

Oh, heh, I forgot that xfs_setsize_buftarg is called a second time by
xfs_setup_devices at the end of fill_super.  xfs_setup_devices is a
better place to call xfs_buftarg_config_atomic_writes.

I don't like the idea of merging the hw atomic write detection into
xfs_setsize_buftarg itself because (a) it gets called for the data
device before we've read the fs blocksize so the validation is
meaningless and (b) that makes xfs_setsize_buftarg's purpose less
cohesive.

--D

Re: [PATCH v9 05/15] xfs: ignore HW which cannot atomic write a single block

[Christoph Hellwig]

On Tue, Apr 29, 2025 at 07:44:46AM -0700, Darrick J. Wong wrote:
> > So this can't be merged into xfs_setsize_buftarg as suggeted last round
> > instead of needing yet another per-device call into the buftarg code?
> 
> Oh, heh, I forgot that xfs_setsize_buftarg is called a second time by
> xfs_setup_devices at the end of fill_super.

That's actually the real call.  The first is just a dummy to have
bt_meta_sectorsize/bt_meta_sectormask initialized because if we didn't
do that some assert in the block layer triggered.  We should probably
remove that call and open code the two assignments..

> I don't like the idea of merging the hw atomic write detection into
> xfs_setsize_buftarg itself because (a) it gets called for the data
> device before we've read the fs blocksize so the validation is
> meaningless and (b) that makes xfs_setsize_buftarg's purpose less
> cohesive.

As explained last round this came up I'd of course rename it if
we did that.  But I can do that later.

Re: [PATCH v9 05/15] xfs: ignore HW which cannot atomic write a single block

[Darrick J. Wong]

On Wed, Apr 30, 2025 at 02:59:06PM +0200, Christoph Hellwig wrote:
> On Tue, Apr 29, 2025 at 07:44:46AM -0700, Darrick J. Wong wrote:
> > > So this can't be merged into xfs_setsize_buftarg as suggeted last round
> > > instead of needing yet another per-device call into the buftarg code?
> > 
> > Oh, heh, I forgot that xfs_setsize_buftarg is called a second time by
> > xfs_setup_devices at the end of fill_super.
> 
> That's actually the real call.  The first is just a dummy to have
> bt_meta_sectorsize/bt_meta_sectormask initialized because if we didn't
> do that some assert in the block layer triggered.  We should probably
> remove that call and open code the two assignments..
> 
> > I don't like the idea of merging the hw atomic write detection into
> > xfs_setsize_buftarg itself because (a) it gets called for the data
> > device before we've read the fs blocksize so the validation is
> > meaningless and (b) that makes xfs_setsize_buftarg's purpose less
> > cohesive.
> 
> As explained last round this came up I'd of course rename it if
> we did that.  But I can do that later.

<nod> Would you be willing to review this patch as it is now and either
you or me can just tack a new cleanup patch on the end?  I tried writing
a patch to clean this up, but ran into questions:

At first I thought that the xfs_setsize_buftarg call in
xfs_alloc_buftarg could be replaced by open-coding the bt_meta_sector*
assignment, checking that bdev_validate_blocksize is ok, and dropping
the sync_blockdev.

Once we get to xfs_setup_devices, we can call xfs_setsize_buftarg on the
three buftargs, and xfs_setsize_buftarg will configure the atomic writes
geometry.

But then as I was reading the patch, it occurred to me that at least for
the data device, we actually /do/ want that sync_blockdev call so that
any dirty pagecache for the superblock actually get written to disk.
Maybe that can go at the end of xfs_open_devices?  But would it be
preferable to sync all the devices prior to trying to read the primary
sb?  I don't think there's a need, but maybe someone else has a
different viewpoint?

--D

Re: [PATCH v9 05/15] xfs: ignore HW which cannot atomic write a single block

[Darrick J. Wong]

On Thu, May 01, 2025 at 09:22:16AM -0700, Darrick J. Wong wrote:
> On Wed, Apr 30, 2025 at 02:59:06PM +0200, Christoph Hellwig wrote:
> > On Tue, Apr 29, 2025 at 07:44:46AM -0700, Darrick J. Wong wrote:
> > > > So this can't be merged into xfs_setsize_buftarg as suggeted last round
> > > > instead of needing yet another per-device call into the buftarg code?
> > > 
> > > Oh, heh, I forgot that xfs_setsize_buftarg is called a second time by
> > > xfs_setup_devices at the end of fill_super.
> > 
> > That's actually the real call.  The first is just a dummy to have
> > bt_meta_sectorsize/bt_meta_sectormask initialized because if we didn't
> > do that some assert in the block layer triggered.  We should probably
> > remove that call and open code the two assignments..
> > 
> > > I don't like the idea of merging the hw atomic write detection into
> > > xfs_setsize_buftarg itself because (a) it gets called for the data
> > > device before we've read the fs blocksize so the validation is
> > > meaningless and (b) that makes xfs_setsize_buftarg's purpose less
> > > cohesive.
> > 
> > As explained last round this came up I'd of course rename it if
> > we did that.  But I can do that later.
> 
> <nod> Would you be willing to review this patch as it is now and either
> you or me can just tack a new cleanup patch on the end?  I tried writing
> a patch to clean this up, but ran into questions:
> 
> At first I thought that the xfs_setsize_buftarg call in
> xfs_alloc_buftarg could be replaced by open-coding the bt_meta_sector*
> assignment, checking that bdev_validate_blocksize is ok, and dropping
> the sync_blockdev.
> 
> Once we get to xfs_setup_devices, we can call xfs_setsize_buftarg on the
> three buftargs, and xfs_setsize_buftarg will configure the atomic writes
> geometry.
> 
> But then as I was reading the patch, it occurred to me that at least for
> the data device, we actually /do/ want that sync_blockdev call so that
> any dirty pagecache for the superblock actually get written to disk.
> Maybe that can go at the end of xfs_open_devices?  But would it be
> preferable to sync all the devices prior to trying to read the primary
> sb?  I don't think there's a need, but maybe someone else has a
> different viewpoint?

Eh, since John posted a V10 I'll just tack my new patches on the end of
that so everyone can look at them.

--D

[PATCH v9.1 05/15] xfs: ignore HW which cannot atomic write a single block

[Darrick J. Wong]

From: Darrick J. Wong <djwong@kernel.org>

Currently only HW which can write at least 1x block is supported.

For supporting atomic writes > 1x block, a CoW-based method will also be
used and this will not be resticted to using HW which can write >= 1x
block.

However for deciding if HW-based atomic writes can be used, we need to
start adding checks for write length < HW min, which complicates the
code.  Indeed, a statx field similar to unit_max_opt should also be
added for this minimum, which is undesirable.

HW which can only write > 1x blocks would be uncommon and quite weird,
so let's just not support it.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
v9.1: move the atomic hw geometry calls to xfs_setup_devices
---
 fs/xfs/xfs_buf.h   |    3 ++-
 fs/xfs/xfs_inode.h |   14 ++------------
 fs/xfs/xfs_buf.c   |   41 ++++++++++++++++++++++++++++++++++-------
 fs/xfs/xfs_super.c |    6 +++++-
 4 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index d0b065a9a9f0d2..6f691779887f77 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -112,7 +112,7 @@ struct xfs_buftarg {
 	struct percpu_counter	bt_readahead_count;
 	struct ratelimit_state	bt_ioerror_rl;
 
-	/* Atomic write unit values */
+	/* Atomic write unit values, bytes */
 	unsigned int		bt_bdev_awu_min;
 	unsigned int		bt_bdev_awu_max;
 
@@ -375,6 +375,7 @@ extern void xfs_free_buftarg(struct xfs_buftarg *);
 extern void xfs_buftarg_wait(struct xfs_buftarg *);
 extern void xfs_buftarg_drain(struct xfs_buftarg *);
 extern int xfs_setsize_buftarg(struct xfs_buftarg *, unsigned int);
+void xfs_buftarg_config_atomic_writes(struct xfs_buftarg *btp);
 
 #define xfs_getsize_buftarg(buftarg)	block_size((buftarg)->bt_bdev)
 #define xfs_readonly_buftarg(buftarg)	bdev_read_only((buftarg)->bt_bdev)
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index bdbbff0d8d9920..d7e2b902ef5c97 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -356,19 +356,9 @@ static inline bool xfs_inode_has_bigrtalloc(const struct xfs_inode *ip)
 	(XFS_IS_REALTIME_INODE(ip) ? \
 		(ip)->i_mount->m_rtdev_targp : (ip)->i_mount->m_ddev_targp)
 
-static inline bool
-xfs_inode_can_hw_atomic_write(
-	struct xfs_inode	*ip)
+static inline bool xfs_inode_can_hw_atomic_write(const struct xfs_inode *ip)
 {
-	struct xfs_mount	*mp = ip->i_mount;
-	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
-
-	if (mp->m_sb.sb_blocksize < target->bt_bdev_awu_min)
-		return false;
-	if (mp->m_sb.sb_blocksize > target->bt_bdev_awu_max)
-		return false;
-
-	return true;
+	return xfs_inode_buftarg(ip)->bt_bdev_awu_max > 0;
 }
 
 /*
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 5ae77ffdc947b1..c1bd5654c3afa8 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1779,6 +1779,40 @@ xfs_init_buftarg(
 	return -ENOMEM;
 }
 
+/*
+ * Configure this buffer target for hardware-assisted atomic writes if the
+ * underlying block device supports is congruent with the filesystem geometry.
+ */
+void
+xfs_buftarg_config_atomic_writes(
+	struct xfs_buftarg	*btp)
+{
+	struct xfs_mount	*mp = btp->bt_mount;
+	unsigned int		min_bytes, max_bytes;
+
+	ASSERT(btp->bt_bdev != NULL);
+
+	if (!bdev_can_atomic_write(btp->bt_bdev))
+		return;
+
+	min_bytes = bdev_atomic_write_unit_min_bytes(btp->bt_bdev);
+	max_bytes = bdev_atomic_write_unit_max_bytes(btp->bt_bdev);
+
+	/*
+	 * Ignore atomic write geometry that is nonsense or doesn't even cover
+	 * a single fsblock.
+	 */
+	if (min_bytes > max_bytes ||
+	    min_bytes > mp->m_sb.sb_blocksize ||
+	    max_bytes < mp->m_sb.sb_blocksize) {
+		min_bytes = 0;
+		max_bytes = 0;
+	}
+
+	btp->bt_bdev_awu_min = min_bytes;
+	btp->bt_bdev_awu_max = max_bytes;
+}
+
 struct xfs_buftarg *
 xfs_alloc_buftarg(
 	struct xfs_mount	*mp,
@@ -1799,13 +1833,6 @@ xfs_alloc_buftarg(
 	btp->bt_daxdev = fs_dax_get_by_bdev(btp->bt_bdev, &btp->bt_dax_part_off,
 					    mp, ops);
 
-	if (bdev_can_atomic_write(btp->bt_bdev)) {
-		btp->bt_bdev_awu_min = bdev_atomic_write_unit_min_bytes(
-						btp->bt_bdev);
-		btp->bt_bdev_awu_max = bdev_atomic_write_unit_max_bytes(
-						btp->bt_bdev);
-	}
-
 	/*
 	 * When allocating the buftargs we have not yet read the super block and
 	 * thus don't know the file system sector size yet.
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index b2dd0c0bf50979..af4c541251d859 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -520,7 +520,8 @@ xfs_open_devices(
 }
 
 /*
- * Setup xfs_mount buffer target pointers based on superblock
+ * Setup xfs_mount buffer target pointers based on superblock, and configure
+ * the atomic write capabilities now that we've validated the blocksize.
  */
 STATIC int
 xfs_setup_devices(
@@ -531,6 +532,7 @@ xfs_setup_devices(
 	error = xfs_setsize_buftarg(mp->m_ddev_targp, mp->m_sb.sb_sectsize);
 	if (error)
 		return error;
+	xfs_buftarg_config_atomic_writes(mp->m_ddev_targp);
 
 	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp) {
 		unsigned int	log_sector_size = BBSIZE;
@@ -541,6 +543,7 @@ xfs_setup_devices(
 					    log_sector_size);
 		if (error)
 			return error;
+		xfs_buftarg_config_atomic_writes(mp->m_logdev_targp);
 	}
 
 	if (mp->m_sb.sb_rtstart) {
@@ -555,6 +558,7 @@ xfs_setup_devices(
 					    mp->m_sb.sb_sectsize);
 		if (error)
 			return error;
+		xfs_buftarg_config_atomic_writes(mp->m_rtdev_targp);
 	}
 
 	return 0;

[PATCH v9 06/15] xfs: allow block allocator to take an alignment hint

[John Garry]

Add a BMAPI flag to provide a hint to the block allocator to align extents
according to the extszhint.

This will be useful for atomic writes to ensure that we are not being
allocated extents which are not suitable (for atomic writes).

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_bmap.c | 5 +++++
 fs/xfs/libxfs/xfs_bmap.h | 6 +++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 63255820b58a..d954f9b8071f 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3312,6 +3312,11 @@ xfs_bmap_compute_alignments(
 		align = xfs_get_cowextsz_hint(ap->ip);
 	else if (ap->datatype & XFS_ALLOC_USERDATA)
 		align = xfs_get_extsz_hint(ap->ip);
+
+	/* Try to align start block to any minimum allocation alignment */
+	if (align > 1 && (ap->flags & XFS_BMAPI_EXTSZALIGN))
+		args->alignment = align;
+
 	if (align) {
 		if (xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, align, 0,
 					ap->eof, 0, ap->conv, &ap->offset,
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index b4d9c6e0f3f9..d5f2729305fa 100644
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -87,6 +87,9 @@ struct xfs_bmalloca {
 /* Do not update the rmap btree.  Used for reconstructing bmbt from rmapbt. */
 #define XFS_BMAPI_NORMAP	(1u << 10)
 
+/* Try to align allocations to the extent size hint */
+#define XFS_BMAPI_EXTSZALIGN	(1u << 11)
+
 #define XFS_BMAPI_FLAGS \
 	{ XFS_BMAPI_ENTIRE,	"ENTIRE" }, \
 	{ XFS_BMAPI_METADATA,	"METADATA" }, \
@@ -98,7 +101,8 @@ struct xfs_bmalloca {
 	{ XFS_BMAPI_REMAP,	"REMAP" }, \
 	{ XFS_BMAPI_COWFORK,	"COWFORK" }, \
 	{ XFS_BMAPI_NODISCARD,	"NODISCARD" }, \
-	{ XFS_BMAPI_NORMAP,	"NORMAP" }
+	{ XFS_BMAPI_NORMAP,	"NORMAP" },\
+	{ XFS_BMAPI_EXTSZALIGN,	"EXTSZALIGN" }
 
 
 static inline int xfs_bmapi_aflag(int w)
-- 
2.31.1

[PATCH v9 07/15] xfs: refactor xfs_reflink_end_cow_extent()

[John Garry]

Refactor xfs_reflink_end_cow_extent() into separate parts which process
the CoW range and commit the transaction.

This refactoring will be used in future for when it is required to commit
a range of extents as a single transaction, similar to how it was done
pre-commit d6f215f359637.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/xfs_reflink.c | 72 ++++++++++++++++++++++++++------------------
 1 file changed, 42 insertions(+), 30 deletions(-)

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index cc3b4df88110..bd711c5bb6bb 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -786,35 +786,19 @@ xfs_reflink_update_quota(
  * requirements as low as possible.
  */
 STATIC int
-xfs_reflink_end_cow_extent(
+xfs_reflink_end_cow_extent_locked(
+	struct xfs_trans	*tp,
 	struct xfs_inode	*ip,
 	xfs_fileoff_t		*offset_fsb,
 	xfs_fileoff_t		end_fsb)
 {
 	struct xfs_iext_cursor	icur;
 	struct xfs_bmbt_irec	got, del, data;
-	struct xfs_mount	*mp = ip->i_mount;
-	struct xfs_trans	*tp;
 	struct xfs_ifork	*ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
-	unsigned int		resblks;
 	int			nmaps;
 	bool			isrt = XFS_IS_REALTIME_INODE(ip);
 	int			error;
 
-	resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
-	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
-			XFS_TRANS_RESERVE, &tp);
-	if (error)
-		return error;
-
-	/*
-	 * Lock the inode.  We have to ijoin without automatic unlock because
-	 * the lead transaction is the refcountbt record deletion; the data
-	 * fork update follows as a deferred log item.
-	 */
-	xfs_ilock(ip, XFS_ILOCK_EXCL);
-	xfs_trans_ijoin(tp, ip, 0);
-
 	/*
 	 * In case of racing, overlapping AIO writes no COW extents might be
 	 * left by the time I/O completes for the loser of the race.  In that
@@ -823,7 +807,7 @@ xfs_reflink_end_cow_extent(
 	if (!xfs_iext_lookup_extent(ip, ifp, *offset_fsb, &icur, &got) ||
 	    got.br_startoff >= end_fsb) {
 		*offset_fsb = end_fsb;
-		goto out_cancel;
+		return 0;
 	}
 
 	/*
@@ -837,7 +821,7 @@ xfs_reflink_end_cow_extent(
 		if (!xfs_iext_next_extent(ifp, &icur, &got) ||
 		    got.br_startoff >= end_fsb) {
 			*offset_fsb = end_fsb;
-			goto out_cancel;
+			return 0;
 		}
 	}
 	del = got;
@@ -846,14 +830,14 @@ xfs_reflink_end_cow_extent(
 	error = xfs_iext_count_extend(tp, ip, XFS_DATA_FORK,
 			XFS_IEXT_REFLINK_END_COW_CNT);
 	if (error)
-		goto out_cancel;
+		return error;
 
 	/* Grab the corresponding mapping in the data fork. */
 	nmaps = 1;
 	error = xfs_bmapi_read(ip, del.br_startoff, del.br_blockcount, &data,
 			&nmaps, 0);
 	if (error)
-		goto out_cancel;
+		return error;
 
 	/* We can only remap the smaller of the two extent sizes. */
 	data.br_blockcount = min(data.br_blockcount, del.br_blockcount);
@@ -882,7 +866,7 @@ xfs_reflink_end_cow_extent(
 		error = xfs_bunmapi(NULL, ip, data.br_startoff,
 				data.br_blockcount, 0, 1, &done);
 		if (error)
-			goto out_cancel;
+			return error;
 		ASSERT(done);
 	}
 
@@ -899,17 +883,45 @@ xfs_reflink_end_cow_extent(
 	/* Remove the mapping from the CoW fork. */
 	xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
 
-	error = xfs_trans_commit(tp);
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
-	if (error)
-		return error;
-
 	/* Update the caller about how much progress we made. */
 	*offset_fsb = del.br_startoff + del.br_blockcount;
 	return 0;
+}
 
-out_cancel:
-	xfs_trans_cancel(tp);
+/*
+ * Remap part of the CoW fork into the data fork.
+ *
+ * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
+ * into the data fork; this function will remap what it can (at the end of the
+ * range) and update @end_fsb appropriately.  Each remap gets its own
+ * transaction because we can end up merging and splitting bmbt blocks for
+ * every remap operation and we'd like to keep the block reservation
+ * requirements as low as possible.
+ */
+STATIC int
+xfs_reflink_end_cow_extent(
+	struct xfs_inode	*ip,
+	xfs_fileoff_t		*offset_fsb,
+	xfs_fileoff_t		end_fsb)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_trans	*tp;
+	unsigned int		resblks;
+	int			error;
+
+	resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
+			XFS_TRANS_RESERVE, &tp);
+	if (error)
+		return error;
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	xfs_trans_ijoin(tp, ip, 0);
+
+	error = xfs_reflink_end_cow_extent_locked(tp, ip, offset_fsb, end_fsb);
+	if (error)
+		xfs_trans_cancel(tp);
+	else
+		error = xfs_trans_commit(tp);
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	return error;
 }
-- 
2.31.1

[PATCH v9 08/15] xfs: refine atomic write size check in xfs_file_write_iter()

[John Garry]

Currently the size of atomic write allowed is fixed at the blocksize.

To start to lift this restriction, partly refactor
xfs_report_atomic_write() to into helpers -
xfs_get_atomic_write_{min, max}() - and use those helpers to find the
per-inode atomic write limits and check according to that.

Also add xfs_get_atomic_write_max_opt() to return the optimal limit, and
just return 0 since large atomics aren't supported yet.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/xfs_file.c | 12 +++++-------
 fs/xfs/xfs_iops.c | 36 +++++++++++++++++++++++++++++++-----
 fs/xfs/xfs_iops.h |  3 +++
 3 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 55bdae44e42a..e8acd6ca8f27 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1032,14 +1032,12 @@ xfs_file_write_iter(
 		return xfs_file_dax_write(iocb, from);
 
 	if (iocb->ki_flags & IOCB_ATOMIC) {
-		/*
-		 * Currently only atomic writing of a single FS block is
-		 * supported. It would be possible to atomic write smaller than
-		 * a FS block, but there is no requirement to support this.
-		 * Note that iomap also does not support this yet.
-		 */
-		if (ocount != ip->i_mount->m_sb.sb_blocksize)
+		if (ocount < xfs_get_atomic_write_min(ip))
 			return -EINVAL;
+
+		if (ocount > xfs_get_atomic_write_max(ip))
+			return -EINVAL;
+
 		ret = generic_atomic_write_valid(iocb, from);
 		if (ret)
 			return ret;
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 22432c300fd7..77a0606e9dc9 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -601,16 +601,42 @@ xfs_report_dioalign(
 		stat->dio_offset_align = stat->dio_read_offset_align;
 }
 
+unsigned int
+xfs_get_atomic_write_min(
+	struct xfs_inode	*ip)
+{
+	if (!xfs_inode_can_hw_atomic_write(ip))
+		return 0;
+
+	return ip->i_mount->m_sb.sb_blocksize;
+}
+
+unsigned int
+xfs_get_atomic_write_max(
+	struct xfs_inode	*ip)
+{
+	if (!xfs_inode_can_hw_atomic_write(ip))
+		return 0;
+
+	return ip->i_mount->m_sb.sb_blocksize;
+}
+
+unsigned int
+xfs_get_atomic_write_max_opt(
+	struct xfs_inode	*ip)
+{
+	return 0;
+}
+
 static void
 xfs_report_atomic_write(
 	struct xfs_inode	*ip,
 	struct kstat		*stat)
 {
-	unsigned int		unit_min = 0, unit_max = 0;
-
-	if (xfs_inode_can_hw_atomic_write(ip))
-		unit_min = unit_max = ip->i_mount->m_sb.sb_blocksize;
-	generic_fill_statx_atomic_writes(stat, unit_min, unit_max, 0);
+	generic_fill_statx_atomic_writes(stat,
+			xfs_get_atomic_write_min(ip),
+			xfs_get_atomic_write_max(ip),
+			xfs_get_atomic_write_max_opt(ip));
 }
 
 STATIC int
diff --git a/fs/xfs/xfs_iops.h b/fs/xfs/xfs_iops.h
index 3c1a2605ffd2..0896f6b8b3b8 100644
--- a/fs/xfs/xfs_iops.h
+++ b/fs/xfs/xfs_iops.h
@@ -19,5 +19,8 @@ int xfs_inode_init_security(struct inode *inode, struct inode *dir,
 extern void xfs_setup_inode(struct xfs_inode *ip);
 extern void xfs_setup_iops(struct xfs_inode *ip);
 extern void xfs_diflags_to_iflags(struct xfs_inode *ip, bool init);
+unsigned int xfs_get_atomic_write_min(struct xfs_inode *ip);
+unsigned int xfs_get_atomic_write_max(struct xfs_inode *ip);
+unsigned int xfs_get_atomic_write_max_opt(struct xfs_inode *ip);
 
 #endif /* __XFS_IOPS_H__ */
-- 
2.31.1

[PATCH v9 09/15] xfs: add xfs_atomic_write_cow_iomap_begin()

[John Garry]

For CoW-based atomic writes, reuse the infrastructure for reflink CoW fork
support.

Add ->iomap_begin() callback xfs_atomic_write_cow_iomap_begin() to create
staging mappings in the CoW fork for atomic write updates.

The general steps in the function are as follows:
- find extent mapping in the CoW fork for the FS block range being written
	- if part or full extent is found, proceed to process found extent
	- if no extent found, map in new blocks to the CoW fork
- convert unwritten blocks in extent if required
- update iomap extent mapping and return

The bulk of this function is quite similar to the processing in
xfs_reflink_allocate_cow(), where we try to find an extent mapping; if
none exists, then allocate a new extent in the CoW fork, convert unwritten
blocks, and return a mapping.

Performance testing has shown the XFS_ILOCK_EXCL locking to be quite
a bottleneck, so this is an area which could be optimised in future.

Christoph Hellwig contributed almost all of the code in
xfs_atomic_write_cow_iomap_begin().

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
[djwong: add a new xfs_can_sw_atomic_write to convey intent better]
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_iomap.c   | 128 +++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iomap.h   |   1 +
 fs/xfs/xfs_mount.h   |   5 ++
 fs/xfs/xfs_reflink.c |   2 +-
 fs/xfs/xfs_reflink.h |   2 +
 fs/xfs/xfs_trace.h   |  22 ++++++++
 6 files changed, 159 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index cb23c8871f81..166fba2ff1ef 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1022,6 +1022,134 @@ const struct iomap_ops xfs_zoned_direct_write_iomap_ops = {
 };
 #endif /* CONFIG_XFS_RT */
 
+static int
+xfs_atomic_write_cow_iomap_begin(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			length,
+	unsigned		flags,
+	struct iomap		*iomap,
+	struct iomap		*srcmap)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+	struct xfs_mount	*mp = ip->i_mount;
+	const xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
+	xfs_fileoff_t		end_fsb = xfs_iomap_end_fsb(mp, offset, length);
+	xfs_filblks_t		count_fsb = end_fsb - offset_fsb;
+	int			nmaps = 1;
+	xfs_filblks_t		resaligned;
+	struct xfs_bmbt_irec	cmap;
+	struct xfs_iext_cursor	icur;
+	struct xfs_trans	*tp;
+	unsigned int		dblocks = 0, rblocks = 0;
+	int			error;
+	u64			seq;
+
+	ASSERT(flags & IOMAP_WRITE);
+	ASSERT(flags & IOMAP_DIRECT);
+
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+
+	if (!xfs_can_sw_atomic_write(mp)) {
+		ASSERT(xfs_can_sw_atomic_write(mp));
+		return -EINVAL;
+	}
+
+	/* blocks are always allocated in this path */
+	if (flags & IOMAP_NOWAIT)
+		return -EAGAIN;
+
+	trace_xfs_iomap_atomic_write_cow(ip, offset, length);
+
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+
+	if (!ip->i_cowfp) {
+		ASSERT(!xfs_is_reflink_inode(ip));
+		xfs_ifork_init_cow(ip);
+	}
+
+	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap))
+		cmap.br_startoff = end_fsb;
+	if (cmap.br_startoff <= offset_fsb) {
+		xfs_trim_extent(&cmap, offset_fsb, count_fsb);
+		goto found;
+	}
+
+	end_fsb = cmap.br_startoff;
+	count_fsb = end_fsb - offset_fsb;
+
+	resaligned = xfs_aligned_fsb_count(offset_fsb, count_fsb,
+			xfs_get_cowextsz_hint(ip));
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+	if (XFS_IS_REALTIME_INODE(ip)) {
+		dblocks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
+		rblocks = resaligned;
+	} else {
+		dblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
+		rblocks = 0;
+	}
+
+	error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, dblocks,
+			rblocks, false, &tp);
+	if (error)
+		return error;
+
+	/* extent layout could have changed since the unlock, so check again */
+	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap))
+		cmap.br_startoff = end_fsb;
+	if (cmap.br_startoff <= offset_fsb) {
+		xfs_trim_extent(&cmap, offset_fsb, count_fsb);
+		xfs_trans_cancel(tp);
+		goto found;
+	}
+
+	/*
+	 * Allocate the entire reservation as unwritten blocks.
+	 *
+	 * Use XFS_BMAPI_EXTSZALIGN to hint at aligning new extents according to
+	 * extszhint, such that there will be a greater chance that future
+	 * atomic writes to that same range will be aligned (and don't require
+	 * this COW-based method).
+	 */
+	error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
+			XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC |
+			XFS_BMAPI_EXTSZALIGN, 0, &cmap, &nmaps);
+	if (error) {
+		xfs_trans_cancel(tp);
+		goto out_unlock;
+	}
+
+	xfs_inode_set_cowblocks_tag(ip);
+	error = xfs_trans_commit(tp);
+	if (error)
+		goto out_unlock;
+
+found:
+	if (cmap.br_state != XFS_EXT_NORM) {
+		error = xfs_reflink_convert_cow_locked(ip, offset_fsb,
+				count_fsb);
+		if (error)
+			goto out_unlock;
+		cmap.br_state = XFS_EXT_NORM;
+	}
+
+	length = XFS_FSB_TO_B(mp, cmap.br_startoff + cmap.br_blockcount);
+	trace_xfs_iomap_found(ip, offset, length - offset, XFS_COW_FORK, &cmap);
+	seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, IOMAP_F_SHARED, seq);
+
+out_unlock:
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+}
+
+const struct iomap_ops xfs_atomic_write_cow_iomap_ops = {
+	.iomap_begin		= xfs_atomic_write_cow_iomap_begin,
+};
+
 static int
 xfs_dax_write_iomap_end(
 	struct inode		*inode,
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index d330c4a581b1..674f8ac1b9bd 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -56,5 +56,6 @@ extern const struct iomap_ops xfs_read_iomap_ops;
 extern const struct iomap_ops xfs_seek_iomap_ops;
 extern const struct iomap_ops xfs_xattr_iomap_ops;
 extern const struct iomap_ops xfs_dax_write_iomap_ops;
+extern const struct iomap_ops xfs_atomic_write_cow_iomap_ops;
 
 #endif /* __XFS_IOMAP_H__*/
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index e5192c12e7ac..e67bc3e91f98 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -464,6 +464,11 @@ static inline bool xfs_has_nonzoned(const struct xfs_mount *mp)
 	return !xfs_has_zoned(mp);
 }
 
+static inline bool xfs_can_sw_atomic_write(struct xfs_mount *mp)
+{
+	return xfs_has_reflink(mp);
+}
+
 /*
  * Some features are always on for v5 file systems, allow the compiler to
  * eliminiate dead code when building without v4 support.
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index bd711c5bb6bb..f5d338916098 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -293,7 +293,7 @@ xfs_bmap_trim_cow(
 	return xfs_reflink_trim_around_shared(ip, imap, shared);
 }
 
-static int
+int
 xfs_reflink_convert_cow_locked(
 	struct xfs_inode	*ip,
 	xfs_fileoff_t		offset_fsb,
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index cc4e92278279..379619f24247 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -35,6 +35,8 @@ int xfs_reflink_allocate_cow(struct xfs_inode *ip, struct xfs_bmbt_irec *imap,
 		bool convert_now);
 extern int xfs_reflink_convert_cow(struct xfs_inode *ip, xfs_off_t offset,
 		xfs_off_t count);
+int xfs_reflink_convert_cow_locked(struct xfs_inode *ip,
+		xfs_fileoff_t offset_fsb, xfs_filblks_t count_fsb);
 
 extern int xfs_reflink_cancel_cow_blocks(struct xfs_inode *ip,
 		struct xfs_trans **tpp, xfs_fileoff_t offset_fsb,
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index e56ba1963160..9554578c6da4 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -1657,6 +1657,28 @@ DEFINE_RW_EVENT(xfs_file_direct_write);
 DEFINE_RW_EVENT(xfs_file_dax_write);
 DEFINE_RW_EVENT(xfs_reflink_bounce_dio_write);
 
+TRACE_EVENT(xfs_iomap_atomic_write_cow,
+	TP_PROTO(struct xfs_inode *ip, xfs_off_t offset, ssize_t count),
+	TP_ARGS(ip, offset, count),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(xfs_ino_t, ino)
+		__field(xfs_off_t, offset)
+		__field(ssize_t, count)
+	),
+	TP_fast_assign(
+		__entry->dev = VFS_I(ip)->i_sb->s_dev;
+		__entry->ino = ip->i_ino;
+		__entry->offset = offset;
+		__entry->count = count;
+	),
+	TP_printk("dev %d:%d ino 0x%llx pos 0x%llx bytecount 0x%zx",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->ino,
+		  __entry->offset,
+		  __entry->count)
+)
+
 DECLARE_EVENT_CLASS(xfs_imap_class,
 	TP_PROTO(struct xfs_inode *ip, xfs_off_t offset, ssize_t count,
 		 int whichfork, struct xfs_bmbt_irec *irec),
-- 
2.31.1

[PATCH v9 10/15] xfs: add large atomic writes checks in xfs_direct_write_iomap_begin()

[John Garry]

For when large atomic writes (> 1x FS block) are supported, there will be
various occasions when HW offload may not be possible.

Such instances include:
- unaligned extent mapping wrt write length
- extent mappings which do not cover the full write, e.g. the write spans
  sparse or mixed-mapping extents
- the write length is greater than HW offload can support
- no hardware support at all

In those cases, we need to fallback to the CoW-based atomic write mode. For
this, report special code -ENOPROTOOPT to inform the caller that HW
offload-based method is not possible.

In addition to the occasions mentioned, if the write covers an unallocated
range, we again judge that we need to rely on the CoW-based method when we
would need to allocate anything more than 1x block. This is because if we
allocate less blocks that is required for the write, then again HW
offload-based method would not be possible. So we are taking a pessimistic
approach to writes covering unallocated space.

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
[djwong: various cleanups]
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_iomap.c | 62 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 60 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 166fba2ff1ef..ff05e6b1b0bb 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -798,6 +798,38 @@ imap_spans_range(
 	return true;
 }
 
+static bool
+xfs_bmap_hw_atomic_write_possible(
+	struct xfs_inode	*ip,
+	struct xfs_bmbt_irec	*imap,
+	xfs_fileoff_t		offset_fsb,
+	xfs_fileoff_t		end_fsb)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	xfs_fsize_t		len = XFS_FSB_TO_B(mp, end_fsb - offset_fsb);
+
+	/*
+	 * atomic writes are required to be naturally aligned for disk blocks,
+	 * which ensures that we adhere to block layer rules that we won't
+	 * straddle any boundary or violate write alignment requirement.
+	 */
+	if (!IS_ALIGNED(imap->br_startblock, imap->br_blockcount))
+		return false;
+
+	/*
+	 * Spanning multiple extents would mean that multiple BIOs would be
+	 * issued, and so would lose atomicity required for REQ_ATOMIC-based
+	 * atomics.
+	 */
+	if (!imap_spans_range(imap, offset_fsb, end_fsb))
+		return false;
+
+	/*
+	 * The ->iomap_begin caller should ensure this, but check anyway.
+	 */
+	return len <= xfs_inode_buftarg(ip)->bt_bdev_awu_max;
+}
+
 static int
 xfs_direct_write_iomap_begin(
 	struct inode		*inode,
@@ -812,9 +844,11 @@ xfs_direct_write_iomap_begin(
 	struct xfs_bmbt_irec	imap, cmap;
 	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
 	xfs_fileoff_t		end_fsb = xfs_iomap_end_fsb(mp, offset, length);
+	xfs_fileoff_t		orig_end_fsb = end_fsb;
 	int			nimaps = 1, error = 0;
 	bool			shared = false;
 	u16			iomap_flags = 0;
+	bool			needs_alloc;
 	unsigned int		lockmode;
 	u64			seq;
 
@@ -875,13 +909,37 @@ xfs_direct_write_iomap_begin(
 				(flags & IOMAP_DIRECT) || IS_DAX(inode));
 		if (error)
 			goto out_unlock;
-		if (shared)
+		if (shared) {
+			if ((flags & IOMAP_ATOMIC) &&
+			    !xfs_bmap_hw_atomic_write_possible(ip, &cmap,
+					offset_fsb, end_fsb)) {
+				error = -ENOPROTOOPT;
+				goto out_unlock;
+			}
 			goto out_found_cow;
+		}
 		end_fsb = imap.br_startoff + imap.br_blockcount;
 		length = XFS_FSB_TO_B(mp, end_fsb) - offset;
 	}
 
-	if (imap_needs_alloc(inode, flags, &imap, nimaps))
+	needs_alloc = imap_needs_alloc(inode, flags, &imap, nimaps);
+
+	if (flags & IOMAP_ATOMIC) {
+		error = -ENOPROTOOPT;
+		/*
+		 * If we allocate less than what is required for the write
+		 * then we may end up with multiple extents, which means that
+		 * REQ_ATOMIC-based cannot be used, so avoid this possibility.
+		 */
+		if (needs_alloc && orig_end_fsb - offset_fsb > 1)
+			goto out_unlock;
+
+		if (!xfs_bmap_hw_atomic_write_possible(ip, &imap, offset_fsb,
+				orig_end_fsb))
+			goto out_unlock;
+	}
+
+	if (needs_alloc)
 		goto allocate_blocks;
 
 	/*
-- 
2.31.1

[PATCH v9 11/15] xfs: commit CoW-based atomic writes atomically

[John Garry]

When completing a CoW-based write, each extent range mapping update is
covered by a separate transaction.

For a CoW-based atomic write, all mappings must be changed at once, so
change to use a single transaction.

Note that there is a limit on the amount of log intent items which can be
fit into a single transaction, but this is being ignored for now since
the count of items for a typical atomic write would be much less than is
typically supported. A typical atomic write would be expected to be 64KB
or less, which means only 16 possible extents unmaps, which is quite
small.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: add tr_atomic_ioend]
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_log_rlimit.c |  4 +++
 fs/xfs/libxfs/xfs_trans_resv.c | 15 +++++++++
 fs/xfs/libxfs/xfs_trans_resv.h |  1 +
 fs/xfs/xfs_file.c              |  5 ++-
 fs/xfs/xfs_reflink.c           | 56 ++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_reflink.h           |  2 ++
 6 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_log_rlimit.c b/fs/xfs/libxfs/xfs_log_rlimit.c
index d3bd6a86c8fe..34bba96d30ca 100644
--- a/fs/xfs/libxfs/xfs_log_rlimit.c
+++ b/fs/xfs/libxfs/xfs_log_rlimit.c
@@ -91,6 +91,7 @@ xfs_log_calc_trans_resv_for_minlogblocks(
 	 */
 	if (xfs_want_minlogsize_fixes(&mp->m_sb)) {
 		xfs_trans_resv_calc(mp, resv);
+		resv->tr_atomic_ioend = M_RES(mp)->tr_atomic_ioend;
 		return;
 	}
 
@@ -107,6 +108,9 @@ xfs_log_calc_trans_resv_for_minlogblocks(
 
 	xfs_trans_resv_calc(mp, resv);
 
+	/* Copy the dynamic transaction reservation types from the running fs */
+	resv->tr_atomic_ioend = M_RES(mp)->tr_atomic_ioend;
+
 	if (xfs_has_reflink(mp)) {
 		/*
 		 * In the early days of reflink, typical log operation counts
diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index 580d00ae2857..a841432abf83 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -1284,6 +1284,15 @@ xfs_calc_namespace_reservations(
 	resp->tr_mkdir.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 }
 
+STATIC void
+xfs_calc_default_atomic_ioend_reservation(
+	struct xfs_mount	*mp,
+	struct xfs_trans_resv	*resp)
+{
+	/* Pick a default that will scale reasonably for the log size. */
+	resp->tr_atomic_ioend = resp->tr_itruncate;
+}
+
 void
 xfs_trans_resv_calc(
 	struct xfs_mount	*mp,
@@ -1378,4 +1387,10 @@ xfs_trans_resv_calc(
 	resp->tr_itruncate.tr_logcount += logcount_adj;
 	resp->tr_write.tr_logcount += logcount_adj;
 	resp->tr_qm_dqalloc.tr_logcount += logcount_adj;
+
+	/*
+	 * Now that we've finished computing the static reservations, we can
+	 * compute the dynamic reservation for atomic writes.
+	 */
+	xfs_calc_default_atomic_ioend_reservation(mp, resp);
 }
diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
index d9d0032cbbc5..670045d417a6 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.h
+++ b/fs/xfs/libxfs/xfs_trans_resv.h
@@ -48,6 +48,7 @@ struct xfs_trans_resv {
 	struct xfs_trans_res	tr_qm_dqalloc;	/* allocate quota on disk */
 	struct xfs_trans_res	tr_sb;		/* modify superblock */
 	struct xfs_trans_res	tr_fsyncts;	/* update timestamps on fsync */
+	struct xfs_trans_res	tr_atomic_ioend; /* untorn write completion */
 };
 
 /* shorthand way of accessing reservation structure */
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e8acd6ca8f27..32883ec8ca2e 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -576,7 +576,10 @@ xfs_dio_write_end_io(
 	nofs_flag = memalloc_nofs_save();
 
 	if (flags & IOMAP_DIO_COW) {
-		error = xfs_reflink_end_cow(ip, offset, size);
+		if (iocb->ki_flags & IOCB_ATOMIC)
+			error = xfs_reflink_end_atomic_cow(ip, offset, size);
+		else
+			error = xfs_reflink_end_cow(ip, offset, size);
 		if (error)
 			goto out;
 	}
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index f5d338916098..218dee76768b 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -984,6 +984,62 @@ xfs_reflink_end_cow(
 	return error;
 }
 
+/*
+ * Fully remap all of the file's data fork at once, which is the critical part
+ * in achieving atomic behaviour.
+ * The regular CoW end path does not use function as to keep the block
+ * reservation per transaction as low as possible.
+ */
+int
+xfs_reflink_end_atomic_cow(
+	struct xfs_inode		*ip,
+	xfs_off_t			offset,
+	xfs_off_t			count)
+{
+	xfs_fileoff_t			offset_fsb;
+	xfs_fileoff_t			end_fsb;
+	int				error = 0;
+	struct xfs_mount		*mp = ip->i_mount;
+	struct xfs_trans		*tp;
+	unsigned int			resblks;
+
+	trace_xfs_reflink_end_cow(ip, offset, count);
+
+	offset_fsb = XFS_B_TO_FSBT(mp, offset);
+	end_fsb = XFS_B_TO_FSB(mp, offset + count);
+
+	/*
+	 * Each remapping operation could cause a btree split, so in the worst
+	 * case that's one for each block.
+	 */
+	resblks = (end_fsb - offset_fsb) *
+			XFS_NEXTENTADD_SPACE_RES(mp, 1, XFS_DATA_FORK);
+
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_atomic_ioend, resblks, 0,
+			XFS_TRANS_RESERVE, &tp);
+	if (error)
+		return error;
+
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	xfs_trans_ijoin(tp, ip, 0);
+
+	while (end_fsb > offset_fsb && !error) {
+		error = xfs_reflink_end_cow_extent_locked(tp, ip, &offset_fsb,
+				end_fsb);
+	}
+	if (error) {
+		trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
+		goto out_cancel;
+	}
+	error = xfs_trans_commit(tp);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+out_cancel:
+	xfs_trans_cancel(tp);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+}
+
 /*
  * Free all CoW staging blocks that are still referenced by the ondisk refcount
  * metadata.  The ondisk metadata does not track which inode created the
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index 379619f24247..412e9b6f2082 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -45,6 +45,8 @@ extern int xfs_reflink_cancel_cow_range(struct xfs_inode *ip, xfs_off_t offset,
 		xfs_off_t count, bool cancel_real);
 extern int xfs_reflink_end_cow(struct xfs_inode *ip, xfs_off_t offset,
 		xfs_off_t count);
+int xfs_reflink_end_atomic_cow(struct xfs_inode *ip, xfs_off_t offset,
+		xfs_off_t count);
 extern int xfs_reflink_recover_cow(struct xfs_mount *mp);
 extern loff_t xfs_reflink_remap_range(struct file *file_in, loff_t pos_in,
 		struct file *file_out, loff_t pos_out, loff_t len,
-- 
2.31.1

[PATCH v9 12/15] xfs: add xfs_file_dio_write_atomic()

[John Garry]

Add xfs_file_dio_write_atomic() for dedicated handling of atomic writes.

Now HW offload will not be required to support atomic writes and is
an optional feature.

CoW-based atomic writes will be supported with out-of-places write and
atomic extent remapping.

Either mode of operation may be used for an atomic write, depending on the
circumstances.

The preferred method is HW offload as it will be faster. If HW offload is
not available then we always use the CoW-based method.  If HW offload is
available but not possible to use, then again we use the CoW-based method.

If available, HW offload would not be possible for the write length
exceeding the HW offload limit, the write spanning multiple extents,
unaligned disk blocks, etc.

Apart from the write exceeding the HW offload limit, other conditions for
HW offload usage can only be detected in the iomap handling for the write.
As such, we use a fallback method to issue the write if we detect in the
->iomap_begin() handler that HW offload is not possible. Special code
-ENOPROTOOPT is returned from ->iomap_begin() to inform that HW offload is
not possible.

In other words, atomic writes are supported on any filesystem that can
perform out of place write remapping atomically (i.e. reflink) up to
some fairly large size.  If the conditions are right (a single correctly
aligned overwrite mapping) then the filesystem will use any available
hardware support to avoid the filesystem metadata updates.

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_file.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 32883ec8ca2e..f4a66ff85748 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -728,6 +728,72 @@ xfs_file_dio_write_zoned(
 	return ret;
 }
 
+/*
+ * Handle block atomic writes
+ *
+ * Two methods of atomic writes are supported:
+ * - REQ_ATOMIC-based, which would typically use some form of HW offload in the
+ *   disk
+ * - COW-based, which uses a COW fork as a staging extent for data updates
+ *   before atomically updating extent mappings for the range being written
+ *
+ */
+static noinline ssize_t
+xfs_file_dio_write_atomic(
+	struct xfs_inode	*ip,
+	struct kiocb		*iocb,
+	struct iov_iter		*from)
+{
+	unsigned int		iolock = XFS_IOLOCK_SHARED;
+	ssize_t			ret, ocount = iov_iter_count(from);
+	const struct iomap_ops	*dops;
+
+	/*
+	 * HW offload should be faster, so try that first if it is already
+	 * known that the write length is not too large.
+	 */
+	if (ocount > xfs_inode_buftarg(ip)->bt_bdev_awu_max)
+		dops = &xfs_atomic_write_cow_iomap_ops;
+	else
+		dops = &xfs_direct_write_iomap_ops;
+
+retry:
+	ret = xfs_ilock_iocb_for_write(iocb, &iolock);
+	if (ret)
+		return ret;
+
+	ret = xfs_file_write_checks(iocb, from, &iolock, NULL);
+	if (ret)
+		goto out_unlock;
+
+	/* Demote similar to xfs_file_dio_write_aligned() */
+	if (iolock == XFS_IOLOCK_EXCL) {
+		xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
+		iolock = XFS_IOLOCK_SHARED;
+	}
+
+	trace_xfs_file_direct_write(iocb, from);
+	ret = iomap_dio_rw(iocb, from, dops, &xfs_dio_write_ops,
+			0, NULL, 0);
+
+	/*
+	 * The retry mechanism is based on the ->iomap_begin method returning
+	 * -ENOPROTOOPT, which would be when the REQ_ATOMIC-based write is not
+	 * possible. The REQ_ATOMIC-based method typically not be possible if
+	 * the write spans multiple extents or the disk blocks are misaligned.
+	 */
+	if (ret == -ENOPROTOOPT && dops == &xfs_direct_write_iomap_ops) {
+		xfs_iunlock(ip, iolock);
+		dops = &xfs_atomic_write_cow_iomap_ops;
+		goto retry;
+	}
+
+out_unlock:
+	if (iolock)
+		xfs_iunlock(ip, iolock);
+	return ret;
+}
+
 /*
  * Handle block unaligned direct I/O writes
  *
@@ -843,6 +909,8 @@ xfs_file_dio_write(
 		return xfs_file_dio_write_unaligned(ip, iocb, from);
 	if (xfs_is_zoned_inode(ip))
 		return xfs_file_dio_write_zoned(ip, iocb, from);
+	if (iocb->ki_flags & IOCB_ATOMIC)
+		return xfs_file_dio_write_atomic(ip, iocb, from);
 	return xfs_file_dio_write_aligned(ip, iocb, from,
 			&xfs_direct_write_iomap_ops, &xfs_dio_write_ops, NULL);
 }
-- 
2.31.1

[PATCH v9 13/15] xfs: add xfs_compute_atomic_write_unit_max()

[John Garry]

Now that CoW-based atomic writes are supported, update the max size of an
atomic write for the data device.

The limit of a CoW-based atomic write will be the limit of the number of
logitems which can fit into a single transaction.

In addition, the max atomic write size needs to be aligned to the agsize.
Limit the size of atomic writes to the greatest power-of-two factor of the
agsize so that allocations for an atomic write will always be aligned
compatibly with the alignment requirements of the storage.

Function xfs_atomic_write_logitems() is added to find the limit the number
of log items which can fit in a single transaction.

Amend the max atomic write computation to create a new transaction
reservation type, and compute the maximum size of an atomic write
completion (in fsblocks) based on this new transaction reservation.
Initially, tr_atomic_write is a clone of tr_itruncate, which provides a
reasonable level of parallelism.  In the next patch, we'll add a mount
option so that sysadmins can configure their own limits.

Signed-off-by: John Garry <john.g.garry@oracle.com>
[djwong: use a new reservation type for atomic write ioends, refactor
group limit calculations]
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
[jpg: update xfs_calc_perag_awu_max() ddev check]
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/libxfs/xfs_trans_resv.c | 94 ++++++++++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_trans_resv.h |  2 +
 fs/xfs/xfs_mount.c             | 81 +++++++++++++++++++++++++++++
 fs/xfs/xfs_mount.h             |  6 +++
 fs/xfs/xfs_reflink.c           | 16 ++++++
 fs/xfs/xfs_reflink.h           |  2 +
 fs/xfs/xfs_trace.h             | 60 ++++++++++++++++++++++
 7 files changed, 261 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index a841432abf83..e73c09fbd24c 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -22,6 +22,12 @@
 #include "xfs_rtbitmap.h"
 #include "xfs_attr_item.h"
 #include "xfs_log.h"
+#include "xfs_defer.h"
+#include "xfs_bmap_item.h"
+#include "xfs_extfree_item.h"
+#include "xfs_rmap_item.h"
+#include "xfs_refcount_item.h"
+#include "xfs_trace.h"
 
 #define _ALLOC	true
 #define _FREE	false
@@ -1394,3 +1400,91 @@ xfs_trans_resv_calc(
 	 */
 	xfs_calc_default_atomic_ioend_reservation(mp, resp);
 }
+
+/*
+ * Return the per-extent and fixed transaction reservation sizes needed to
+ * complete an atomic write.
+ */
+STATIC unsigned int
+xfs_calc_atomic_write_ioend_geometry(
+	struct xfs_mount	*mp,
+	unsigned int		*step_size)
+{
+	const unsigned int	efi = xfs_efi_log_space(1);
+	const unsigned int	efd = xfs_efd_log_space(1);
+	const unsigned int	rui = xfs_rui_log_space(1);
+	const unsigned int	rud = xfs_rud_log_space();
+	const unsigned int	cui = xfs_cui_log_space(1);
+	const unsigned int	cud = xfs_cud_log_space();
+	const unsigned int	bui = xfs_bui_log_space(1);
+	const unsigned int	bud = xfs_bud_log_space();
+
+	/*
+	 * Maximum overhead to complete an atomic write ioend in software:
+	 * remove data fork extent + remove cow fork extent + map extent into
+	 * data fork.
+	 *
+	 * tx0: Creates a BUI and a CUI and that's all it needs.
+	 *
+	 * tx1: Roll to finish the BUI.  Need space for the BUD, an RUI, and
+	 * enough space to relog the CUI (== CUI + CUD).
+	 *
+	 * tx2: Roll again to finish the RUI.  Need space for the RUD and space
+	 * to relog the CUI.
+	 *
+	 * tx3: Roll again, need space for the CUD and possibly a new EFI.
+	 *
+	 * tx4: Roll again, need space for an EFD.
+	 *
+	 * If the extent referenced by the pair of BUI/CUI items is not the one
+	 * being currently processed, then we need to reserve space to relog
+	 * both items.
+	 */
+	const unsigned int	tx0 = bui + cui;
+	const unsigned int	tx1 = bud + rui + cui + cud;
+	const unsigned int	tx2 = rud + cui + cud;
+	const unsigned int	tx3 = cud + efi;
+	const unsigned int	tx4 = efd;
+	const unsigned int	relog = bui + bud + cui + cud;
+
+	const unsigned int	per_intent = max(max3(tx0, tx1, tx2),
+						 max3(tx3, tx4, relog));
+
+	/* Overhead to finish one step of each intent item type */
+	const unsigned int	f1 = xfs_calc_finish_efi_reservation(mp, 1);
+	const unsigned int	f2 = xfs_calc_finish_rui_reservation(mp, 1);
+	const unsigned int	f3 = xfs_calc_finish_cui_reservation(mp, 1);
+	const unsigned int	f4 = xfs_calc_finish_bui_reservation(mp, 1);
+
+	/* We only finish one item per transaction in a chain */
+	*step_size = max(f4, max3(f1, f2, f3));
+
+	return per_intent;
+}
+
+/*
+ * Compute the maximum size (in fsblocks) of atomic writes that we can complete
+ * given the existing log reservations.
+ */
+xfs_extlen_t
+xfs_calc_max_atomic_write_fsblocks(
+	struct xfs_mount		*mp)
+{
+	const struct xfs_trans_res	*resv = &M_RES(mp)->tr_atomic_ioend;
+	unsigned int			per_intent = 0;
+	unsigned int			step_size = 0;
+	unsigned int			ret = 0;
+
+	if (resv->tr_logres > 0) {
+		per_intent = xfs_calc_atomic_write_ioend_geometry(mp,
+				&step_size);
+
+		if (resv->tr_logres >= step_size)
+			ret = (resv->tr_logres - step_size) / per_intent;
+	}
+
+	trace_xfs_calc_max_atomic_write_fsblocks(mp, per_intent, step_size,
+			resv->tr_logres, ret);
+
+	return ret;
+}
diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
index 670045d417a6..a6d303b83688 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.h
+++ b/fs/xfs/libxfs/xfs_trans_resv.h
@@ -121,4 +121,6 @@ unsigned int xfs_calc_itruncate_reservation_minlogsize(struct xfs_mount *mp);
 unsigned int xfs_calc_write_reservation_minlogsize(struct xfs_mount *mp);
 unsigned int xfs_calc_qm_dqalloc_reservation_minlogsize(struct xfs_mount *mp);
 
+xfs_extlen_t xfs_calc_max_atomic_write_fsblocks(struct xfs_mount *mp);
+
 #endif	/* __XFS_TRANS_RESV_H__ */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 1082b322e6d6..eebd5e7d1ab6 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -666,6 +666,80 @@ xfs_agbtree_compute_maxlevels(
 	mp->m_agbtree_maxlevels = max(levels, mp->m_refc_maxlevels);
 }
 
+/* Maximum atomic write IO size that the kernel allows. */
+static inline xfs_extlen_t xfs_calc_atomic_write_max(struct xfs_mount *mp)
+{
+	return rounddown_pow_of_two(XFS_B_TO_FSB(mp, MAX_RW_COUNT));
+}
+
+static inline unsigned int max_pow_of_two_factor(const unsigned int nr)
+{
+	return 1 << (ffs(nr) - 1);
+}
+
+/*
+ * If the data device advertises atomic write support, limit the size of data
+ * device atomic writes to the greatest power-of-two factor of the AG size so
+ * that every atomic write unit aligns with the start of every AG.  This is
+ * required so that the per-AG allocations for an atomic write will always be
+ * aligned compatibly with the alignment requirements of the storage.
+ *
+ * If the data device doesn't advertise atomic writes, then there are no
+ * alignment restrictions and the largest out-of-place write we can do
+ * ourselves is the number of blocks that user files can allocate from any AG.
+ */
+static inline xfs_extlen_t xfs_calc_perag_awu_max(struct xfs_mount *mp)
+{
+	if (mp->m_ddev_targp->bt_bdev_awu_min > 0)
+		return max_pow_of_two_factor(mp->m_sb.sb_agblocks);
+	return mp->m_ag_max_usable;
+}
+
+/*
+ * Reflink on the realtime device requires rtgroups, and atomic writes require
+ * reflink.
+ *
+ * If the realtime device advertises atomic write support, limit the size of
+ * data device atomic writes to the greatest power-of-two factor of the rtgroup
+ * size so that every atomic write unit aligns with the start of every rtgroup.
+ * This is required so that the per-rtgroup allocations for an atomic write
+ * will always be aligned compatibly with the alignment requirements of the
+ * storage.
+ *
+ * If the rt device doesn't advertise atomic writes, then there are no
+ * alignment restrictions and the largest out-of-place write we can do
+ * ourselves is the number of blocks that user files can allocate from any
+ * rtgroup.
+ */
+static inline xfs_extlen_t xfs_calc_rtgroup_awu_max(struct xfs_mount *mp)
+{
+	struct xfs_groups	*rgs = &mp->m_groups[XG_TYPE_RTG];
+
+	if (mp->m_rtdev_targp && mp->m_rtdev_targp->bt_bdev_awu_min > 0)
+		return max_pow_of_two_factor(rgs->blocks);
+	return rgs->blocks;
+}
+
+/* Compute the maximum atomic write unit size for each section. */
+static inline void
+xfs_calc_atomic_write_unit_max(
+	struct xfs_mount	*mp)
+{
+	struct xfs_groups	*ags = &mp->m_groups[XG_TYPE_AG];
+	struct xfs_groups	*rgs = &mp->m_groups[XG_TYPE_RTG];
+
+	const xfs_extlen_t	max_write = xfs_calc_atomic_write_max(mp);
+	const xfs_extlen_t	max_ioend = xfs_reflink_max_atomic_cow(mp);
+	const xfs_extlen_t	max_agsize = xfs_calc_perag_awu_max(mp);
+	const xfs_extlen_t	max_rgsize = xfs_calc_rtgroup_awu_max(mp);
+
+	ags->awu_max = min3(max_write, max_ioend, max_agsize);
+	rgs->awu_max = min3(max_write, max_ioend, max_rgsize);
+
+	trace_xfs_calc_atomic_write_unit_max(mp, max_write, max_ioend,
+			max_agsize, max_rgsize);
+}
+
 /* Compute maximum possible height for realtime btree types for this fs. */
 static inline void
 xfs_rtbtree_compute_maxlevels(
@@ -1089,6 +1163,13 @@ xfs_mountfs(
 	if (mp->m_rtdev_targp && mp->m_rtdev_targp != mp->m_ddev_targp)
 		xfs_buftarg_config_atomic_writes(mp->m_rtdev_targp);
 
+	/*
+	 * Pre-calculate atomic write unit max.  This involves computations
+	 * derived from transaction reservations, so we must do this after the
+	 * log is fully initialized.
+	 */
+	xfs_calc_atomic_write_unit_max(mp);
+
 	return 0;
 
  out_agresv:
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index e67bc3e91f98..e2abf31438e0 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -119,6 +119,12 @@ struct xfs_groups {
 	 * SMR hard drives.
 	 */
 	xfs_fsblock_t		start_fsb;
+
+	/*
+	 * Maximum length of an atomic write for files stored in this
+	 * collection of allocation groups, in fsblocks.
+	 */
+	xfs_extlen_t		awu_max;
 };
 
 struct xfs_freecounter {
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 218dee76768b..ad3bcb76d805 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1040,6 +1040,22 @@ xfs_reflink_end_atomic_cow(
 	return error;
 }
 
+/* Compute the largest atomic write that we can complete through software. */
+xfs_extlen_t
+xfs_reflink_max_atomic_cow(
+	struct xfs_mount	*mp)
+{
+	/* We cannot do any atomic writes without out of place writes. */
+	if (!xfs_can_sw_atomic_write(mp))
+		return 0;
+
+	/*
+	 * Atomic write limits must always be a power-of-2, according to
+	 * generic_atomic_write_valid.
+	 */
+	return rounddown_pow_of_two(xfs_calc_max_atomic_write_fsblocks(mp));
+}
+
 /*
  * Free all CoW staging blocks that are still referenced by the ondisk refcount
  * metadata.  The ondisk metadata does not track which inode created the
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index 412e9b6f2082..36cda724da89 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -68,4 +68,6 @@ extern int xfs_reflink_update_dest(struct xfs_inode *dest, xfs_off_t newlen,
 
 bool xfs_reflink_supports_rextsize(struct xfs_mount *mp, unsigned int rextsize);
 
+xfs_extlen_t xfs_reflink_max_atomic_cow(struct xfs_mount *mp);
+
 #endif /* __XFS_REFLINK_H */
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 9554578c6da4..d5ae00f8e04c 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -170,6 +170,66 @@ DEFINE_ATTR_LIST_EVENT(xfs_attr_list_notfound);
 DEFINE_ATTR_LIST_EVENT(xfs_attr_leaf_list);
 DEFINE_ATTR_LIST_EVENT(xfs_attr_node_list);
 
+TRACE_EVENT(xfs_calc_atomic_write_unit_max,
+	TP_PROTO(struct xfs_mount *mp, unsigned int max_write,
+		 unsigned int max_ioend, unsigned int max_agsize,
+		 unsigned int max_rgsize),
+	TP_ARGS(mp, max_write, max_ioend, max_agsize, max_rgsize),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(unsigned int, max_write)
+		__field(unsigned int, max_ioend)
+		__field(unsigned int, max_agsize)
+		__field(unsigned int, max_rgsize)
+		__field(unsigned int, data_awu_max)
+		__field(unsigned int, rt_awu_max)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->max_write = max_write;
+		__entry->max_ioend = max_ioend;
+		__entry->max_agsize = max_agsize;
+		__entry->max_rgsize = max_rgsize;
+		__entry->data_awu_max = mp->m_groups[XG_TYPE_AG].awu_max;
+		__entry->rt_awu_max = mp->m_groups[XG_TYPE_RTG].awu_max;
+	),
+	TP_printk("dev %d:%d max_write %u max_ioend %u max_agsize %u max_rgsize %u data_awu_max %u rt_awu_max %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->max_write,
+		  __entry->max_ioend,
+		  __entry->max_agsize,
+		  __entry->max_rgsize,
+		  __entry->data_awu_max,
+		  __entry->rt_awu_max)
+);
+
+TRACE_EVENT(xfs_calc_max_atomic_write_fsblocks,
+	TP_PROTO(struct xfs_mount *mp, unsigned int per_intent,
+		 unsigned int step_size, unsigned int logres,
+		 unsigned int blockcount),
+	TP_ARGS(mp, per_intent, step_size, logres, blockcount),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(unsigned int, per_intent)
+		__field(unsigned int, step_size)
+		__field(unsigned int, logres)
+		__field(unsigned int, blockcount)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->per_intent = per_intent;
+		__entry->step_size = step_size;
+		__entry->logres = logres;
+		__entry->blockcount = blockcount;
+	),
+	TP_printk("dev %d:%d per_intent %u step_size %u logres %u blockcount %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->per_intent,
+		  __entry->step_size,
+		  __entry->logres,
+		  __entry->blockcount)
+);
+
 TRACE_EVENT(xlog_intent_recovery_failed,
 	TP_PROTO(struct xfs_mount *mp, const struct xfs_defer_op_type *ops,
 		 int error),
-- 
2.31.1

Re: [PATCH v9 13/15] xfs: add xfs_compute_atomic_write_unit_max()

[John Garry]

On 25/04/2025 17:45, John Garry wrote:
> +static inline xfs_extlen_t xfs_calc_perag_awu_max(struct xfs_mount *mp)
> +{
> +	if (mp->m_ddev_targp->bt_bdev_awu_min > 0)
> +		return max_pow_of_two_factor(mp->m_sb.sb_agblocks);
> +	return mp->m_ag_max_usable;

I think that this should be rounddown_pow_of_two(mp->m_ag_max_usable)

ditto for rt

I will fix (unless disagree).

Re: [PATCH v9 13/15] xfs: add xfs_compute_atomic_write_unit_max()

[Darrick J. Wong]

On Wed, Apr 30, 2025 at 08:52:00AM +0100, John Garry wrote:
> On 25/04/2025 17:45, John Garry wrote:
> > +static inline xfs_extlen_t xfs_calc_perag_awu_max(struct xfs_mount *mp)
> > +{
> > +	if (mp->m_ddev_targp->bt_bdev_awu_min > 0)
> > +		return max_pow_of_two_factor(mp->m_sb.sb_agblocks);
> > +	return mp->m_ag_max_usable;
> 
> I think that this should be rounddown_pow_of_two(mp->m_ag_max_usable)
> 
> ditto for rt
> 
> I will fix (unless disagree).

I don't think this needs fixing.  If there's no hardware support on the
device, then we can do any size of atomic write that we want.

--D

Re: [PATCH v9 13/15] xfs: add xfs_compute_atomic_write_unit_max()

[John Garry]

On 01/05/2025 05:30, Darrick J. Wong wrote:
> On Wed, Apr 30, 2025 at 08:52:00AM +0100, John Garry wrote:
>> On 25/04/2025 17:45, John Garry wrote:
>>> +static inline xfs_extlen_t xfs_calc_perag_awu_max(struct xfs_mount *mp)
>>> +{
>>> +	if (mp->m_ddev_targp->bt_bdev_awu_min > 0)
>>> +		return max_pow_of_two_factor(mp->m_sb.sb_agblocks);
>>> +	return mp->m_ag_max_usable;
>> I think that this should be rounddown_pow_of_two(mp->m_ag_max_usable)
>>
>> ditto for rt
>>
>> I will fix (unless disagree).
> I don't think this needs fixing.  If there's no hardware support on the
> device, then we can do any size of atomic write that we want.

Check man pages for statx:

stx_atomic_write_unit_min
stx_atomic_write_unit_max
               ... These values are each guaranteed to be
               a power-of-2.

Same is enforced for size for RWF_ATOMIC.

Re: [PATCH v9 13/15] xfs: add xfs_compute_atomic_write_unit_max()

[Darrick J. Wong]

On Thu, May 01, 2025 at 06:00:12AM +0100, John Garry wrote:
> On 01/05/2025 05:30, Darrick J. Wong wrote:
> > On Wed, Apr 30, 2025 at 08:52:00AM +0100, John Garry wrote:
> > > On 25/04/2025 17:45, John Garry wrote:
> > > > +static inline xfs_extlen_t xfs_calc_perag_awu_max(struct xfs_mount *mp)
> > > > +{
> > > > +	if (mp->m_ddev_targp->bt_bdev_awu_min > 0)
> > > > +		return max_pow_of_two_factor(mp->m_sb.sb_agblocks);
> > > > +	return mp->m_ag_max_usable;
> > > I think that this should be rounddown_pow_of_two(mp->m_ag_max_usable)
> > > 
> > > ditto for rt
> > > 
> > > I will fix (unless disagree).
> > I don't think this needs fixing.  If there's no hardware support on the
> > device, then we can do any size of atomic write that we want.
> 
> Check man pages for statx:
> 
> stx_atomic_write_unit_min
> stx_atomic_write_unit_max
>               ... These values are each guaranteed to be
>               a power-of-2.
> 
> Same is enforced for size for RWF_ATOMIC.

Ok then.

--D

[PATCH v9 14/15] xfs: update atomic write limits

[John Garry]

Update the limits returned from xfs_get_atomic_write_{min, max, max_opt)().

No reflink support always means no CoW-based atomic writes.

For updating xfs_get_atomic_write_min(), we support blocksize only and that
depends on HW or reflink support.

For updating xfs_get_atomic_write_max(), for no reflink, we are limited to
blocksize but only if HW support. Otherwise we are limited to combined
limit in mp->m_atomic_write_unit_max.

For updating xfs_get_atomic_write_max_opt(), ultimately we are limited by
the bdev atomic write limit. If xfs_get_atomic_write_max() does not report
 > 1x blocksize, then just continue to report 0 as before.

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
[djwong: update comments in the helper functions]
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_file.c |  2 +-
 fs/xfs/xfs_iops.c | 52 +++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index f4a66ff85748..48254a72071b 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1557,7 +1557,7 @@ xfs_file_open(
 	if (xfs_is_shutdown(XFS_M(inode->i_sb)))
 		return -EIO;
 	file->f_mode |= FMODE_NOWAIT | FMODE_CAN_ODIRECT;
-	if (xfs_inode_can_hw_atomic_write(XFS_I(inode)))
+	if (xfs_get_atomic_write_min(XFS_I(inode)) > 0)
 		file->f_mode |= FMODE_CAN_ATOMIC_WRITE;
 	return generic_file_open(inode, file);
 }
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 77a0606e9dc9..8cddbb7c149b 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -605,27 +605,67 @@ unsigned int
 xfs_get_atomic_write_min(
 	struct xfs_inode	*ip)
 {
-	if (!xfs_inode_can_hw_atomic_write(ip))
-		return 0;
+	struct xfs_mount	*mp = ip->i_mount;
+
+	/*
+	 * If we can complete an atomic write via atomic out of place writes,
+	 * then advertise a minimum size of one fsblock.  Without this
+	 * mechanism, we can only guarantee atomic writes up to a single LBA.
+	 *
+	 * If out of place writes are not available, we can guarantee an atomic
+	 * write of exactly one single fsblock if the bdev will make that
+	 * guarantee for us.
+	 */
+	if (xfs_inode_can_hw_atomic_write(ip) || xfs_can_sw_atomic_write(mp))
+		return mp->m_sb.sb_blocksize;
 
-	return ip->i_mount->m_sb.sb_blocksize;
+	return 0;
 }
 
 unsigned int
 xfs_get_atomic_write_max(
 	struct xfs_inode	*ip)
 {
-	if (!xfs_inode_can_hw_atomic_write(ip))
+	struct xfs_mount	*mp = ip->i_mount;
+
+	/*
+	 * If out of place writes are not available, we can guarantee an atomic
+	 * write of exactly one single fsblock if the bdev will make that
+	 * guarantee for us.
+	 */
+	if (!xfs_can_sw_atomic_write(mp)) {
+		if (xfs_inode_can_hw_atomic_write(ip))
+			return mp->m_sb.sb_blocksize;
 		return 0;
+	}
 
-	return ip->i_mount->m_sb.sb_blocksize;
+	/*
+	 * If we can complete an atomic write via atomic out of place writes,
+	 * then advertise a maximum size of whatever we can complete through
+	 * that means.  Hardware support is reported via max_opt, not here.
+	 */
+	if (XFS_IS_REALTIME_INODE(ip))
+		return XFS_FSB_TO_B(mp, mp->m_groups[XG_TYPE_RTG].awu_max);
+	return XFS_FSB_TO_B(mp, mp->m_groups[XG_TYPE_AG].awu_max);
 }
 
 unsigned int
 xfs_get_atomic_write_max_opt(
 	struct xfs_inode	*ip)
 {
-	return 0;
+	unsigned int		awu_max = xfs_get_atomic_write_max(ip);
+
+	/* if the max is 1x block, then just keep behaviour that opt is 0 */
+	if (awu_max <= ip->i_mount->m_sb.sb_blocksize)
+		return 0;
+
+	/*
+	 * Advertise the maximum size of an atomic write that we can tell the
+	 * block device to perform for us.  In general the bdev limit will be
+	 * less than our out of place write limit, but we don't want to exceed
+	 * the awu_max.
+	 */
+	return min(awu_max, xfs_inode_buftarg(ip)->bt_bdev_awu_max);
 }
 
 static void
-- 
2.31.1

[PATCH v9 15/15] xfs: allow sysadmins to specify a maximum atomic write limit at mount time

[John Garry]

From: "Darrick J. Wong" <djwong@kernel.org>

Introduce a mount option to allow sysadmins to specify the maximum size
of an atomic write.  If the filesystem can work with the supplied value,
that becomes the new guaranteed maximum.

The value mustn't be too big for the existing filesystem geometry (max
write size, max AG/rtgroup size).  We dynamically recompute the
tr_atomic_write transaction reservation based on the given block size,
check that the current log size isn't less than the new minimum log size
constraints, and set a new maximum.

The actual software atomic write max is still computed based off of
tr_atomic_ioend the same way it has for the past few commits.  Note also
that xfs_calc_atomic_write_log_geometry is non-static because mkfs will
need that.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 Documentation/admin-guide/xfs.rst | 11 +++++
 fs/xfs/libxfs/xfs_trans_resv.c    | 69 ++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_trans_resv.h    |  4 ++
 fs/xfs/xfs_mount.c                | 80 ++++++++++++++++++++++++++++++-
 fs/xfs/xfs_mount.h                |  6 +++
 fs/xfs/xfs_super.c                | 58 +++++++++++++++++++++-
 fs/xfs/xfs_trace.h                | 33 +++++++++++++
 7 files changed, 259 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst
index 5becb441c3cb..a18328a5fb93 100644
--- a/Documentation/admin-guide/xfs.rst
+++ b/Documentation/admin-guide/xfs.rst
@@ -151,6 +151,17 @@ When mounting an XFS filesystem, the following options are accepted.
 	optional, and the log section can be separate from the data
 	section or contained within it.
 
+  max_atomic_write=value
+	Set the maximum size of an atomic write.  The size may be
+	specified in bytes, in kilobytes with a "k" suffix, in megabytes
+	with a "m" suffix, or in gigabytes with a "g" suffix.  The size
+	cannot be larger than the maximum write size, larger than the
+	size of any allocation group, or larger than the size of a
+	remapping operation that the log can complete atomically.
+
+	The default value is to set the maximum I/O completion size
+	to allow each CPU to handle one at a time.
+
   max_open_zones=value
 	Specify the max number of zones to keep open for writing on a
 	zoned rt device. Many open zones aids file data separation
diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index e73c09fbd24c..86a111d0f2fc 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -1488,3 +1488,72 @@ xfs_calc_max_atomic_write_fsblocks(
 
 	return ret;
 }
+
+/*
+ * Compute the log blocks and transaction reservation needed to complete an
+ * atomic write of a given number of blocks.  Worst case, each block requires
+ * separate handling.  A return value of 0 means something went wrong.
+ */
+xfs_extlen_t
+xfs_calc_atomic_write_log_geometry(
+	struct xfs_mount	*mp,
+	xfs_extlen_t		blockcount,
+	unsigned int		*new_logres)
+{
+	struct xfs_trans_res	*curr_res = &M_RES(mp)->tr_atomic_ioend;
+	uint			old_logres = curr_res->tr_logres;
+	unsigned int		per_intent, step_size;
+	unsigned int		logres;
+	xfs_extlen_t		min_logblocks;
+
+	ASSERT(blockcount > 0);
+
+	xfs_calc_default_atomic_ioend_reservation(mp, M_RES(mp));
+
+	per_intent = xfs_calc_atomic_write_ioend_geometry(mp, &step_size);
+
+	/* Check for overflows */
+	if (check_mul_overflow(blockcount, per_intent, &logres) ||
+	    check_add_overflow(logres, step_size, &logres))
+		return 0;
+
+	curr_res->tr_logres = logres;
+	min_logblocks = xfs_log_calc_minimum_size(mp);
+	curr_res->tr_logres = old_logres;
+
+	trace_xfs_calc_max_atomic_write_log_geometry(mp, per_intent, step_size,
+			blockcount, min_logblocks, logres);
+
+	*new_logres = logres;
+	return min_logblocks;
+}
+
+/*
+ * Compute the transaction reservation needed to complete an out of place
+ * atomic write of a given number of blocks.
+ */
+int
+xfs_calc_atomic_write_reservation(
+	struct xfs_mount	*mp,
+	xfs_extlen_t		blockcount)
+{
+	unsigned int		new_logres;
+	xfs_extlen_t		min_logblocks;
+
+	/*
+	 * If the caller doesn't ask for a specific atomic write size, then
+	 * use the defaults.
+	 */
+	if (blockcount == 0) {
+		xfs_calc_default_atomic_ioend_reservation(mp, M_RES(mp));
+		return 0;
+	}
+
+	min_logblocks = xfs_calc_atomic_write_log_geometry(mp, blockcount,
+			&new_logres);
+	if (!min_logblocks || min_logblocks > mp->m_sb.sb_logblocks)
+		return -EINVAL;
+
+	M_RES(mp)->tr_atomic_ioend.tr_logres = new_logres;
+	return 0;
+}
diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
index a6d303b83688..336279e0fc61 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.h
+++ b/fs/xfs/libxfs/xfs_trans_resv.h
@@ -122,5 +122,9 @@ unsigned int xfs_calc_write_reservation_minlogsize(struct xfs_mount *mp);
 unsigned int xfs_calc_qm_dqalloc_reservation_minlogsize(struct xfs_mount *mp);
 
 xfs_extlen_t xfs_calc_max_atomic_write_fsblocks(struct xfs_mount *mp);
+xfs_extlen_t xfs_calc_atomic_write_log_geometry(struct xfs_mount *mp,
+		xfs_extlen_t blockcount, unsigned int *new_logres);
+int xfs_calc_atomic_write_reservation(struct xfs_mount *mp,
+		xfs_extlen_t blockcount);
 
 #endif	/* __XFS_TRANS_RESV_H__ */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index eebd5e7d1ab6..a6cea25b3a7f 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -740,6 +740,82 @@ xfs_calc_atomic_write_unit_max(
 			max_agsize, max_rgsize);
 }
 
+/*
+ * Try to set the atomic write maximum to a new value that we got from
+ * userspace via mount option.
+ */
+int
+xfs_set_max_atomic_write_opt(
+	struct xfs_mount	*mp,
+	unsigned long long	new_max_bytes)
+{
+	const xfs_filblks_t	new_max_fsbs = XFS_B_TO_FSBT(mp, new_max_bytes);
+	const xfs_extlen_t	max_write = xfs_calc_atomic_write_max(mp);
+	const xfs_extlen_t	max_group =
+		max(mp->m_groups[XG_TYPE_AG].blocks,
+		    mp->m_groups[XG_TYPE_RTG].blocks);
+	const xfs_extlen_t	max_group_write =
+		max(xfs_calc_perag_awu_max(mp), xfs_calc_rtgroup_awu_max(mp));
+	int			error;
+
+	if (new_max_bytes == 0)
+		goto set_limit;
+
+	ASSERT(max_write <= U32_MAX);
+
+	/* generic_atomic_write_valid enforces power of two length */
+	if (!is_power_of_2(new_max_bytes)) {
+		xfs_warn(mp,
+ "max atomic write size of %llu bytes is not a power of 2",
+				new_max_bytes);
+		return -EINVAL;
+	}
+
+	if (new_max_bytes & mp->m_blockmask) {
+		xfs_warn(mp,
+ "max atomic write size of %llu bytes not aligned with fsblock",
+				new_max_bytes);
+		return -EINVAL;
+	}
+
+	if (new_max_fsbs > max_write) {
+		xfs_warn(mp,
+ "max atomic write size of %lluk cannot be larger than max write size %lluk",
+				new_max_bytes >> 10,
+				XFS_FSB_TO_B(mp, max_write) >> 10);
+		return -EINVAL;
+	}
+
+	if (new_max_fsbs > max_group) {
+		xfs_warn(mp,
+ "max atomic write size of %lluk cannot be larger than allocation group size %lluk",
+				new_max_bytes >> 10,
+				XFS_FSB_TO_B(mp, max_group) >> 10);
+		return -EINVAL;
+	}
+
+	if (new_max_fsbs > max_group_write) {
+		xfs_warn(mp,
+ "max atomic write size of %lluk cannot be larger than max allocation group write size %lluk",
+				new_max_bytes >> 10,
+				XFS_FSB_TO_B(mp, max_group_write) >> 10);
+		return -EINVAL;
+	}
+
+set_limit:
+	error = xfs_calc_atomic_write_reservation(mp, new_max_fsbs);
+	if (error) {
+		xfs_warn(mp,
+ "cannot support completing atomic writes of %lluk",
+				new_max_bytes >> 10);
+		return error;
+	}
+
+	xfs_calc_atomic_write_unit_max(mp);
+	mp->m_awu_max_bytes = new_max_bytes;
+	return 0;
+}
+
 /* Compute maximum possible height for realtime btree types for this fs. */
 static inline void
 xfs_rtbtree_compute_maxlevels(
@@ -1168,7 +1244,9 @@ xfs_mountfs(
 	 * derived from transaction reservations, so we must do this after the
 	 * log is fully initialized.
 	 */
-	xfs_calc_atomic_write_unit_max(mp);
+	error = xfs_set_max_atomic_write_opt(mp, mp->m_awu_max_bytes);
+	if (error)
+		goto out_agresv;
 
 	return 0;
 
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index e2abf31438e0..5b5df70570c0 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -237,6 +237,9 @@ typedef struct xfs_mount {
 	unsigned int		m_max_open_zones;
 	unsigned int		m_zonegc_low_space;
 
+	/* max_atomic_write mount option value */
+	unsigned long long	m_awu_max_bytes;
+
 	/*
 	 * Bitsets of per-fs metadata that have been checked and/or are sick.
 	 * Callers must hold m_sb_lock to access these two fields.
@@ -804,4 +807,7 @@ static inline void xfs_mod_sb_delalloc(struct xfs_mount *mp, int64_t delta)
 	percpu_counter_add(&mp->m_delalloc_blks, delta);
 }
 
+int xfs_set_max_atomic_write_opt(struct xfs_mount *mp,
+		unsigned long long new_max_bytes);
+
 #endif	/* __XFS_MOUNT_H__ */
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index b2dd0c0bf509..4cdb161a1bb8 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -111,7 +111,7 @@ enum {
 	Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
 	Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
 	Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum, Opt_max_open_zones,
-	Opt_lifetime, Opt_nolifetime,
+	Opt_lifetime, Opt_nolifetime, Opt_max_atomic_write,
 };
 
 static const struct fs_parameter_spec xfs_fs_parameters[] = {
@@ -159,6 +159,7 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
 	fsparam_u32("max_open_zones",	Opt_max_open_zones),
 	fsparam_flag("lifetime",	Opt_lifetime),
 	fsparam_flag("nolifetime",	Opt_nolifetime),
+	fsparam_string("max_atomic_write",	Opt_max_atomic_write),
 	{}
 };
 
@@ -241,6 +242,9 @@ xfs_fs_show_options(
 
 	if (mp->m_max_open_zones)
 		seq_printf(m, ",max_open_zones=%u", mp->m_max_open_zones);
+	if (mp->m_awu_max_bytes)
+		seq_printf(m, ",max_atomic_write=%lluk",
+				mp->m_awu_max_bytes >> 10);
 
 	return 0;
 }
@@ -1334,6 +1338,42 @@ suffix_kstrtoint(
 	return ret;
 }
 
+static int
+suffix_kstrtoull(
+	const char		*s,
+	unsigned int		base,
+	unsigned long long	*res)
+{
+	int			last, shift_left_factor = 0;
+	unsigned long long	_res;
+	char			*value;
+	int			ret = 0;
+
+	value = kstrdup(s, GFP_KERNEL);
+	if (!value)
+		return -ENOMEM;
+
+	last = strlen(value) - 1;
+	if (value[last] == 'K' || value[last] == 'k') {
+		shift_left_factor = 10;
+		value[last] = '\0';
+	}
+	if (value[last] == 'M' || value[last] == 'm') {
+		shift_left_factor = 20;
+		value[last] = '\0';
+	}
+	if (value[last] == 'G' || value[last] == 'g') {
+		shift_left_factor = 30;
+		value[last] = '\0';
+	}
+
+	if (kstrtoull(value, base, &_res))
+		ret = -EINVAL;
+	kfree(value);
+	*res = _res << shift_left_factor;
+	return ret;
+}
+
 static inline void
 xfs_fs_warn_deprecated(
 	struct fs_context	*fc,
@@ -1518,6 +1558,14 @@ xfs_fs_parse_param(
 	case Opt_nolifetime:
 		parsing_mp->m_features |= XFS_FEAT_NOLIFETIME;
 		return 0;
+	case Opt_max_atomic_write:
+		if (suffix_kstrtoull(param->string, 10,
+				     &parsing_mp->m_awu_max_bytes)) {
+			xfs_warn(parsing_mp,
+ "max atomic write size must be positive integer");
+			return -EINVAL;
+		}
+		return 0;
 	default:
 		xfs_warn(parsing_mp, "unknown mount option [%s].", param->key);
 		return -EINVAL;
@@ -2114,6 +2162,14 @@ xfs_fs_reconfigure(
 	if (error)
 		return error;
 
+	/* Validate new max_atomic_write option before making other changes */
+	if (mp->m_awu_max_bytes != new_mp->m_awu_max_bytes) {
+		error = xfs_set_max_atomic_write_opt(mp,
+				new_mp->m_awu_max_bytes);
+		if (error)
+			return error;
+	}
+
 	/* inode32 -> inode64 */
 	if (xfs_has_small_inums(mp) && !xfs_has_small_inums(new_mp)) {
 		mp->m_features &= ~XFS_FEAT_SMALL_INUMS;
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index d5ae00f8e04c..01d284a1c759 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -230,6 +230,39 @@ TRACE_EVENT(xfs_calc_max_atomic_write_fsblocks,
 		  __entry->blockcount)
 );
 
+TRACE_EVENT(xfs_calc_max_atomic_write_log_geometry,
+	TP_PROTO(struct xfs_mount *mp, unsigned int per_intent,
+		 unsigned int step_size, unsigned int blockcount,
+		 unsigned int min_logblocks, unsigned int logres),
+	TP_ARGS(mp, per_intent, step_size, blockcount, min_logblocks, logres),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(unsigned int, per_intent)
+		__field(unsigned int, step_size)
+		__field(unsigned int, blockcount)
+		__field(unsigned int, min_logblocks)
+		__field(unsigned int, cur_logblocks)
+		__field(unsigned int, logres)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->per_intent = per_intent;
+		__entry->step_size = step_size;
+		__entry->blockcount = blockcount;
+		__entry->min_logblocks = min_logblocks;
+		__entry->cur_logblocks = mp->m_sb.sb_logblocks;
+		__entry->logres = logres;
+	),
+	TP_printk("dev %d:%d per_intent %u step_size %u blockcount %u min_logblocks %u logblocks %u logres %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->per_intent,
+		  __entry->step_size,
+		  __entry->blockcount,
+		  __entry->min_logblocks,
+		  __entry->cur_logblocks,
+		  __entry->logres)
+);
+
 TRACE_EVENT(xlog_intent_recovery_failed,
 	TP_PROTO(struct xfs_mount *mp, const struct xfs_defer_op_type *ops,
 		 int error),
-- 
2.31.1

Re: [PATCH v9 15/15] xfs: allow sysadmins to specify a maximum atomic write limit at mount time

[Christoph Hellwig]

So I guess the property variant didn't work out based on the replies
from Darrick last round?

Re: [PATCH v9 15/15] xfs: allow sysadmins to specify a maximum atomic write limit at mount time

[Darrick J. Wong]

On Tue, Apr 29, 2025 at 02:22:11PM +0200, Christoph Hellwig wrote:
> So I guess the property variant didn't work out based on the replies
> from Darrick last round?

Correct.  Calling setxattr on the property wouldn't call
xfs_set_max_atomic_write_opt to change the operational limit, and I
don't want to start up the whole magic xattrs discussion again by making
xfs_xattr_set do extra things if name=="trusted.xfs:max_atomic_write".

(Though iirc you were the most opposed to magic xattrs, and my
opposition is 45% yuck factor and 55% "hch will nak it anyway" ;) )

--D

Re: [PATCH v9 00/15] large atomic writes for xfs

[John Garry]

Hi Christoph,

At this point, is your only issue now with
05/15 xfs: ignore HW which cannot atomic write a single block
?

I am not sure on 15/15...

Thanks,
John

Re: [PATCH v9 00/15] large atomic writes for xfs

[Darrick J. Wong]

On Wed, Apr 30, 2025 at 03:14:04PM +0100, John Garry wrote:
> Hi Christoph,
> 
> At this point, is your only issue now with
> 05/15 xfs: ignore HW which cannot atomic write a single block
> ?
> 
> I am not sure on 15/15...

This series still needs reviews of patches 2, 3, 5, and 15, if I'm not
mistaken.

--D

> Thanks,
> John
> 

Re: [PATCH v9 00/15] large atomic writes for xfs

[John Garry]

On 01/05/2025 05:31, Darrick J. Wong wrote:
> On Wed, Apr 30, 2025 at 03:14:04PM +0100, John Garry wrote:
>> Hi Christoph,
>>
>> At this point, is your only issue now with
>> 05/15 xfs: ignore HW which cannot atomic write a single block
>> ?
>>
>> I am not sure on 15/15...
> 
> This series still needs reviews of patches 2, 3, 5, and 15, if I'm not
> mistaken.

I can review 2 and 3, but I am not familiar with the code so I don't 
think that there is much value in that. I feel that very few are. So who 
else will?

Re: [PATCH v9 00/15] large atomic writes for xfs

[Christoph Hellwig]

On Wed, Apr 30, 2025 at 03:14:04PM +0100, John Garry wrote:
> Hi Christoph,
>
> At this point, is your only issue now with
> 05/15 xfs: ignore HW which cannot atomic write a single block
> ?
>
> I am not sure on 15/15...

I don't like it, but it's a mount option and nothing persistent so
I should probably just shut up.