[v6,07/28] btrfs: disable fallocate in HMZONED mode
diff mbox series

Message ID 20191213040915.3502922-8-naohiro.aota@wdc.com
State New
Headers show
Series
  • btrfs: zoned block device support
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Commit Message

Naohiro Aota Dec. 13, 2019, 4:08 a.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 HMZONED mode for now.

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

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/file.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Josef Bacik Dec. 13, 2019, 4:26 p.m. UTC | #1
On 12/12/19 11:08 PM, Naohiro Aota wrote:
> 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 for now.
> 
> In the future, we may be able to implement "in-memory" fallocate() in
> HMZONED mode by utilizing space_info->bytes_may_use or so.
> 
> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef

Patch
diff mbox series

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 0cb43b682789..22373d00428b 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -3170,6 +3170,10 @@  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))