[PATCH 03/21] fs/bdev: Add atomic write support info to statx

John Garry
2023-09-29T10:29:07Z

From: Prasad Singamsetty <prasad.singamsetty@oracle.com>

Extend statx system call to return additional info for atomic write support
support if the specified file is a block device.

Add initial support for a block device.

Signed-off-by: Prasad Singamsetty <prasad.singamsetty@oracle.com>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
block/bdev.c | 33 +++++++++++++++++++++++----------
fs/stat.c | 15 ++++++++-------
include/linux/blkdev.h | 4 ++--
include/linux/stat.h | 2 ++
include/uapi/linux/stat.h | 7 ++++++-
5 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index f3b13aa1b7d4..037a3d9ecbcb 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -1028,24 +1028,37 @@ void sync_bdevs(bool wait)
iput(old_inode);
}

+#define BDEV_STATX_SUPPORTED_MSK (STATX_DIOALIGN | STATX_WRITE_ATOMIC)
+
/*
- * Handle STATX_DIOALIGN for block devices.
- *
- * Note that the inode passed to this is the inode of a block device node file,
- * not the block device's internal inode. Therefore it is *not* valid to use
- * I_BDEV() here; the block device has to be looked up by i_rdev instead.
+ * Handle STATX_{DIOALIGN, WRITE_ATOMIC} for block devices.
*/
-void bdev_statx_dioalign(struct inode *inode, struct kstat *stat)
+void bdev_statx(struct dentry *dentry, struct kstat *stat, u32 request_mask)
{
struct block_device *bdev;

- bdev = blkdev_get_no_open(inode->i_rdev);
+ if (!(request_mask & BDEV_STATX_SUPPORTED_MSK))
+ return;
+
+ bdev = blkdev_get_no_open(d_backing_inode(dentry)->i_rdev);
if (!bdev)
return;

- stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
- stat->dio_offset_align = bdev_logical_block_size(bdev);
- stat->result_mask |= STATX_DIOALIGN;
+ if (request_mask & STATX_DIOALIGN) {
+ stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
+ stat->dio_offset_align = bdev_logical_block_size(bdev);
+ stat->result_mask |= STATX_DIOALIGN;
+ }
+
+ if (request_mask & STATX_WRITE_ATOMIC) {
+ stat->atomic_write_unit_min =
+ queue_atomic_write_unit_min_bytes(bdev->bd_queue);
+ stat->atomic_write_unit_max =
+ queue_atomic_write_unit_max_bytes(bdev->bd_queue);
+ stat->attributes |= STATX_ATTR_WRITE_ATOMIC;
+ stat->attributes_mask |= STATX_ATTR_WRITE_ATOMIC;
+ stat->result_mask |= STATX_WRITE_ATOMIC;
+ }

blkdev_put_no_open(bdev);
}
diff --git a/fs/stat.c b/fs/stat.c
index d43a5cc1bfa4..b840e58f41fa 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -250,13 +250,12 @@ static int vfs_statx(int dfd, struct filename *filename, int flags,
stat->attributes |= STATX_ATTR_MOUNT_ROOT;
stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;

- /* Handle STATX_DIOALIGN for block devices. */
- if (request_mask & STATX_DIOALIGN) {
- struct inode *inode = d_backing_inode(path.dentry);
-
- if (S_ISBLK(inode->i_mode))
- bdev_statx_dioalign(inode, stat);
- }
+ /* If this is a block device inode, override the filesystem
+ * attributes with the block device specific parameters
+ * that need to be obtained from the bdev backing inode
+ */
+ if (S_ISBLK(d_backing_inode(path.dentry)->i_mode))
+ bdev_statx(path.dentry, stat, request_mask);

path_put(&path);
if (retry_estale(error, lookup_flags)) {
@@ -649,6 +648,8 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
tmp.stx_mnt_id = stat->mnt_id;
tmp.stx_dio_mem_align = stat->dio_mem_align;
tmp.stx_dio_offset_align = stat->dio_offset_align;
+ tmp.stx_atomic_write_unit_min = stat->atomic_write_unit_min;
+ tmp.stx_atomic_write_unit_max = stat->atomic_write_unit_max;

return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c10e47bdb34f..f70988083734 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1533,7 +1533,7 @@ int sync_blockdev(struct block_device *bdev);
int sync_blockdev_range(struct block_device *bdev, loff_t lstart, loff_t lend);
int sync_blockdev_nowait(struct block_device *bdev);
void sync_bdevs(bool wait);
-void bdev_statx_dioalign(struct inode *inode, struct kstat *stat);
+void bdev_statx(struct dentry *dentry, struct kstat *stat, u32 request_mask);
void printk_all_partitions(void);
int __init early_lookup_bdev(const char *pathname, dev_t *dev);
#else
@@ -1551,7 +1551,7 @@ static inline int sync_blockdev_nowait(struct block_device *bdev)
static inline void sync_bdevs(bool wait)
{
}
-static inline void bdev_statx_dioalign(struct inode *inode, struct kstat *stat)
+static inline void bdev_statx(struct dentry *dentry, struct kstat *stat, u32 request_mask)
{
}
static inline void printk_all_partitions(void)
diff --git a/include/linux/stat.h b/include/linux/stat.h
index 52150570d37a..dfa69ecfaacf 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -53,6 +53,8 @@ struct kstat {
u32 dio_mem_align;
u32 dio_offset_align;
u64 change_cookie;
+ u32 atomic_write_unit_max;
+ u32 atomic_write_unit_min;
};

/* These definitions are internal to the kernel for now. Mainly used by nfsd. */
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 7cab2c65d3d7..c99d7cac2aa6 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -127,7 +127,10 @@ struct statx {
__u32 stx_dio_mem_align; /* Memory buffer alignment for direct I/O */
__u32 stx_dio_offset_align; /* File offset alignment for direct I/O */
/* 0xa0 */
- __u64 __spare3[12]; /* Spare space for future expansion */
+ __u32 stx_atomic_write_unit_max;
+ __u32 stx_atomic_write_unit_min;
+ /* 0xb0 */
+ __u64 __spare3[11]; /* Spare space for future expansion */
/* 0x100 */
};

@@ -154,6 +157,7 @@ struct statx {
#define STATX_BTIME 0x00000800U /* Want/got stx_btime */
#define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */
#define STATX_DIOALIGN 0x00002000U /* Want/got direct I/O alignment info */
+#define STATX_WRITE_ATOMIC 0x00004000U /* Want/got atomic_write_* fields */

#define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */

@@ -189,6 +193,7 @@ struct statx {
#define STATX_ATTR_MOUNT_ROOT 0x00002000 /* Root of a mount */
#define STATX_ATTR_VERITY 0x00100000 /* [I] Verity protected file */
#define STATX_ATTR_DAX 0x00200000 /* File is currently in DAX state */
+#define STATX_ATTR_WRITE_ATOMIC 0x00400000 /* File supports atomic write operations */

#endif /* _UAPI_LINUX_STAT_H */
--
2.31.1