[PATCH v2 3/5] fs, xfs: introduce FALLOC_FL_UNSEAL_BLOCK_MAP

Dan Williams
2017-08-04T02:32:36Z

Provide an explicit fallocate operation type for clearing the
S_IOMAP_IMMUTABLE flag. Like the enable case it requires CAP_IMMUTABLE
and it can only be performed while no process has the file mapped.

Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Suggested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
fs/open.c | 17 +++++++++++------
fs/xfs/xfs_bmap_util.c | 42 ++++++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_bmap_util.h | 3 +++
fs/xfs/xfs_file.c | 4 +++-
include/linux/falloc.h | 3 ++-
include/uapi/linux/falloc.h | 1 +
6 files changed, 62 insertions(+), 8 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index e3aae59785ae..ccfd8d3becc8 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -274,13 +274,17 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
return -EINVAL;

/*
- * Seal block map operation should only be used exclusively, and
- * with the IMMUTABLE capability.
+ * Seal/unseal block map operations should only be used
+ * exclusively, and with the IMMUTABLE capability.
*/
- if (mode & FALLOC_FL_SEAL_BLOCK_MAP) {
+ if (mode & (FALLOC_FL_SEAL_BLOCK_MAP | FALLOC_FL_UNSEAL_BLOCK_MAP)) {
if (!capable(CAP_LINUX_IMMUTABLE))
return -EPERM;
- if (mode & ~FALLOC_FL_SEAL_BLOCK_MAP)
+ if (mode == (FALLOC_FL_SEAL_BLOCK_MAP
+ | FALLOC_FL_UNSEAL_BLOCK_MAP))
+ return -EINVAL;
+ if (mode & ~(FALLOC_FL_SEAL_BLOCK_MAP
+ | FALLOC_FL_UNSEAL_BLOCK_MAP))
return -EINVAL;
}

@@ -303,9 +307,10 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
return -ETXTBSY;

/*
- * We cannot allow any allocation changes on an iomap immutable file
+ * We cannot allow any allocation changes on an iomap immutable
+ * file, but we can allow clearing the immutable state.
*/
- if (IS_IOMAP_IMMUTABLE(inode))
+ if (IS_IOMAP_IMMUTABLE(inode) && !(mode & FALLOC_FL_UNSEAL_BLOCK_MAP))
return -ETXTBSY;

/*
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 46d8eb9e19fc..70ac2d33ab27 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1494,6 +1494,48 @@ xfs_seal_file_space(
return error;
}

+int
+xfs_unseal_file_space(
+ struct xfs_inode *ip,
+ xfs_off_t offset,
+ xfs_off_t len)
+{
+ struct inode *inode = VFS_I(ip);
+ struct address_space *mapping = inode->i_mapping;
+ int error;
+
+ ASSERT(xfs_isilocked(ip, XFS_MMAPLOCK_EXCL));
+
+ if (offset)
+ return -EINVAL;
+
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ /*
+ * It does not make sense to unseal less than the full range of
+ * the file.
+ */
+ error = -EINVAL;
+ if (len < i_size_read(inode))
+ goto out_unlock;
+
+ /*
+ * Provide safety against one thread changing the policy of not
+ * requiring fsync/msync (for block allocations) behind another
+ * thread's back.
+ */
+ error = -EBUSY;
+ if (mapping_mapped(mapping))
+ goto out_unlock;
+
+ inode->i_flags &= ~S_IOMAP_IMMUTABLE;
+ error = 0;
+
+out_unlock:
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+ return error;
+}
+
/*
* @next_fsb will keep track of the extent currently undergoing shift.
* @stop_fsb will keep track of the extent at which we have to stop.
diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h
index 5115a32a2483..b64653a75942 100644
--- a/fs/xfs/xfs_bmap_util.h
+++ b/fs/xfs/xfs_bmap_util.h
@@ -62,6 +62,9 @@ int xfs_insert_file_space(struct xfs_inode *, xfs_off_t offset,
xfs_off_t len);
int xfs_seal_file_space(struct xfs_inode *, xfs_off_t offset,
xfs_off_t len);
+int xfs_unseal_file_space(struct xfs_inode *, xfs_off_t offset,
+ xfs_off_t len);
+

/* EOF block manipulation functions */
bool xfs_can_free_eofblocks(struct xfs_inode *ip, bool force);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e21121530a90..833f77700be2 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -740,7 +740,7 @@ xfs_file_write_iter(
(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | \
FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE | \
FALLOC_FL_INSERT_RANGE | FALLOC_FL_UNSHARE_RANGE | \
- FALLOC_FL_SEAL_BLOCK_MAP)
+ FALLOC_FL_SEAL_BLOCK_MAP | FALLOC_FL_UNSEAL_BLOCK_MAP)

STATIC long
xfs_file_fallocate(
@@ -840,6 +840,8 @@ xfs_file_fallocate(
XFS_BMAPI_PREALLOC);
} else if (mode & FALLOC_FL_SEAL_BLOCK_MAP) {
error = xfs_seal_file_space(ip, offset, len);
+ } else if (mode & FALLOC_FL_UNSEAL_BLOCK_MAP) {
+ error = xfs_unseal_file_space(ip, offset, len);
} else
error = xfs_alloc_file_space(ip, offset, len,
XFS_BMAPI_PREALLOC);
diff --git a/include/linux/falloc.h b/include/linux/falloc.h
index 48546c6fbec7..b22c1368ed1e 100644
--- a/include/linux/falloc.h
+++ b/include/linux/falloc.h
@@ -27,6 +27,7 @@ struct space_resv {
FALLOC_FL_ZERO_RANGE | \
FALLOC_FL_INSERT_RANGE | \
FALLOC_FL_UNSHARE_RANGE | \
- FALLOC_FL_SEAL_BLOCK_MAP)
+ FALLOC_FL_SEAL_BLOCK_MAP | \
+ FALLOC_FL_UNSEAL_BLOCK_MAP)

#endif /* _FALLOC_H_ */
diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
index 39076975bf6f..a4949e1a2dae 100644
--- a/include/uapi/linux/falloc.h
+++ b/include/uapi/linux/falloc.h
@@ -95,4 +95,5 @@
* with the punch, zero, collapse, or insert range modes.
*/
#define FALLOC_FL_SEAL_BLOCK_MAP 0x080
+#define FALLOC_FL_UNSEAL_BLOCK_MAP 0x100
#endif /* _UAPI_FALLOC_H_ */