[PATCH 1/4 RESEND] btrfs: fix zstd compression parameter

[Anand Jain]

We let to pass zstd compression parameter even if its not fully written.
For example:
  btrfs prop set /btrfs compression zst
  btrfs prop get /btrfs compression
     compression=zst

zlib and lzo are fine.

Fix it by using the expected number of char in strncmp().

Signed-off-by: Anand Jain <anand.j...@oracle.com>
Reviewed-by: Nikolay Borisov <nbori...@suse.com>
---
 fs/btrfs/props.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index f1a8be67f639..3cc007e3c7f8 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -304,7 +304,7 @@ static int prop_compression_apply(struct inode *inode, 
const char *value,
                btrfs_set_fs_incompat(fs_info, COMPRESS_LZO);
        } else if (!strncmp("zlib", value, 4)) {
                type = BTRFS_COMPRESS_ZLIB;
-       } else if (!strncmp("zstd", value, len)) {
+       } else if (!strncmp("zstd", value, 4)) {
                type = BTRFS_COMPRESS_ZSTD;
                btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD);
        } else {
-- 
1.8.3.1