From: Naohiro Aota <naohiro.aota@wdc.com>
Date: Tue, 10 Nov 2020 11:26:12 +0000 (+0900)
Subject: btrfs: disable fallocate in ZONED mode
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f1569c4c10a1e9320b92486d73043c6138859cc5;p=linux.git

btrfs: disable fallocate in ZONED mode

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 similar, so this
returns EOPNOTSUPP.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index d808928dded6f..0e41459b8de66 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -3308,6 +3308,10 @@ static long btrfs_fallocate(struct file *file, int mode,
 	int blocksize = btrfs_inode_sectorsize(BTRFS_I(inode));
 	int ret;
 
+	/* Do not allow fallocate in ZONED mode */
+	if (btrfs_is_zoned(btrfs_sb(inode->i_sb)))
+		return -EOPNOTSUPP;
+
 	alloc_start = round_down(offset, blocksize);
 	alloc_end = round_up(offset + len, blocksize);
 	cur_offset = alloc_start;