[PATCH] Btrfs: disable online scrub repair on ro cases

[Liu Bo <bo.li.liu@oracle.com>]

This disables repair process on ro cases as it can cause system
to be unresponsive on the ASSERT() in repair_io_failure().

This can happen when scrub is running and a hardware error pops up,
we should fallback to ro mounts gracefully instead of being unresponsive.

Reported-by: Codebird <codebird@birds-are-nice.me>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
 fs/btrfs/scrub.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 2907a77..d6dd2f5 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -682,6 +682,9 @@ static int scrub_fixup_readpage(u64 inum, u64 offset, u64 root, void *fixup_ctx)
 	struct btrfs_root *local_root;
 	int srcu_index;
 
+	if (root->fs_info->sb->s_flags & MS_RDONLY)
+		return -EROFS;
+
 	key.objectid = root;
 	key.type = BTRFS_ROOT_ITEM_KEY;
 	key.offset = (u64)-1;
-- 
2.5.0