[PATCH][SRU][TRUSTY] Btrfs: fix transaction abortion when remounting btrfs from RW to RO

[Colin King]

From: Wang Shilong <wangsl.fnst at cn.fujitsu.com>

BugLink: http://bugs.launchpad.net/bugs/1411320

Steps to reproduce:
 # mkfs.btrfs -f /dev/sda8
 # mount /dev/sda8 /mnt -o flushoncommit
 # dd if=/dev/zero of=/mnt/data bs=4k count=102400 &
 # mount /dev/sda8 /mnt -o remount, ro

When remounting RW to RO, the logic is to firstly set flag
to RO and then commit transaction, however with option
flushoncommit enabled,we will do RO check within committing
transaction, so we get a transaction abortion here.

Actually,here check is wrong, we should check if FS_STATE_ERROR
is set, fix it.

Reported-by: Qu Wenruo <quwenruo at cn.fujitsu.com>
Suggested-by: Miao Xie <miaox at cn.fujitsu.com>
Signed-off-by: Wang Shilong <wangsl.fnst at cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik at fb.com>
Signed-off-by: Chris Mason <clm at fb.com>
(cherry picked from commit 2c21b4d733d6e50514e30ffd87110364ddda695b)
Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 fs/btrfs/inode.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f4a870a..387b6fb 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8290,7 +8290,7 @@ int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
 {
 	int ret;
 
-	if (root->fs_info->sb->s_flags & MS_RDONLY)
+	if (test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state))
 		return -EROFS;
 
 	ret = __start_delalloc_inodes(root, delay_iput);
@@ -8316,7 +8316,7 @@ int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, int delay_iput)
 	struct list_head splice;
 	int ret;
 
-	if (fs_info->sb->s_flags & MS_RDONLY)
+	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
 		return -EROFS;
 
 	INIT_LIST_HEAD(&splice);
-- 
1.7.9.5