[PATCH] Btrfs: clear compress-force when remounting with compress option

[Wang Shilong <wangsl.fnst@cn.fujitsu.com>]

Steps to reproduce:
 # mkfs.btrfs -f /dev/sdb
 # mount /dev/sdb /mnt -o compress-force=lzo
 # mount /dev/sdb /mnt -o remount,compress=zlib
 # cat /proc/mounts

Remounting from compress-force to compress could not clear compress-force
option. The problem is there is no way for users to clear compress-force
option separately.

Fix this problem by clearing @FORCE_COMPRESS flag when remounting to
compress=xxx.

Suggested-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
---
 fs/btrfs/super.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4662d92..c3bb35f 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -513,6 +513,14 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 					btrfs_info(root->fs_info,
 						   "btrfs: use %s compression",
 						   compress_type);
+				/*
+				 * If we remount from compress-force=xxx to
+				 * compress=xxx, we need clear FORCE_COMPRESS
+				 * flag, otherwise, there is no way for users
+				 * to disable forcible compression separately.
+				 */
+				btrfs_clear_and_info(root, FORCE_COMPRESS,
+						     "compress is not forced anymore");
 			}
 			break;
 		case Opt_ssd:
-- 
1.9.0