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Subject[RFC PATCH 05/17] btrfs: disable fallocate in HMZONED mode
Date
fallocate() is implemented by reserving actual extent instead of
reservations. This can result in exposing the sequential write constraint
of host-managed zoned block devices to the application, which would break
the POSIX semantic for the fallocated file. To avoid this, report
fallocate() as not supported when in HMZONED mode.

Signed-off-by: Naohiro Aota <naota@elisp.net>
---
fs/btrfs/file.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 095f0bb86bb7..6f4546ccb57d 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2993,6 +2993,10 @@ static long btrfs_fallocate(struct file *file, int mode,
alloc_end = round_up(offset + len, blocksize);
cur_offset = alloc_start;

+ /* Do not allow fallocate in HMZONED mode */
+ if (btrfs_fs_incompat(btrfs_sb(inode->i_sb), HMZONED))
+ return -EOPNOTSUPP;
+
/* Make sure we aren't being give some crap mode */
if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
FALLOC_FL_ZERO_RANGE))
--
2.18.0
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