From: Nikolay Borisov <nborisov@suse.com>
Date: Tue, 7 May 2019 10:23:46 +0300
Git-commit: 5f791ec31f535f62a2dc06b37c3a69e5e268b5db
Patch-mainline: 5.3
References: bsc#1174438
Subject: [PATCH] btrfs: Return EAGAIN if we can't start no snpashot
 write in check_can_nocow

The first thing code does in check_can_nocow is trying to block
concurrent snapshots. If this fails (due to snpashot already being in
progress) the function returns ENOSPC which makes no sense. Instead
return EAGAIN. Despite this return value not being propagated to callers
it's good practice to return the closest in terms of semantics error
code. No functional changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index cdc998eb5ac1..5711d6851b63 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1557,7 +1557,7 @@ static noinline int check_can_nocow(struct btrfs_inode *inode, loff_t pos,
 
 	ret = btrfs_start_write_no_snapshoting(root);
 	if (!ret)
-		return -ENOSPC;
+		return -EAGAIN;
 
 	lockstart = round_down(pos, fs_info->sectorsize);
 	lockend = round_up(pos + *write_bytes,
-- 
2.26.2