[v8,08/41] btrfs: disable fallocate in ZONED mode

Commit Message

Naohiro Aota Oct. 1, 2020, 6:36 p.m. UTC

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 ZONED mode for now.

In the future, we may be able to implement "in-memory" fallocate() in ZONED
mode by utilizing space_info->bytes_may_use or so.

Reviewed-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Josef Bacik <[e-mail]>
Signed-off-by: Naohiro Aota <[e-mail]>
---
 fs/btrfs/file.c | 4 ++++
 1 file changed, 4 insertions(+)

Patch

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 038e0afaf3d0..60a01e1347ba 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -3341,6 +3341,10 @@  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 ZONED mode */
+	if (btrfs_fs_incompat(btrfs_sb(inode->i_sb), ZONED))
+		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))