[PATCH] f2fs: don't set RO when shutting down f2fs

[Jaegeuk Kim]

Shutdown does not check the error of thaw_super due to readonly, which
causes a deadlock like below.

f2fs_ioc_shutdown(F2FS_GOING_DOWN_FULLSYNC)        issue_discard_thread
 - bdev_freeze
  - freeze_super
 - f2fs_stop_checkpoint()
  - f2fs_handle_critical_error                     - sb_start_write
    - set RO                                         - waiting
 - bdev_thaw
  - thaw_super_locked
    - return -EINVAL, if sb_rdonly()
 - f2fs_stop_discard_thread
  -> wait for kthread_stop(discard_thread);

Reported-by: "Light Hsieh (謝明燈)" <Light.Hsieh@xxxxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
 fs/f2fs/super.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index df9765b41dac..ba6288e870c5 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4135,9 +4135,16 @@ void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char reason,
 	if (shutdown)
 		set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
 
-	/* continue filesystem operators if errors=continue */
-	if (continue_fs || f2fs_readonly(sb))
+	/*
+	 * Continue filesystem operators if errors=continue. Should not set
+	 * RO by shutdown, since RO bypasses thaw_super which can hang the
+	 * system.
+	 */
+	if (continue_fs || f2fs_readonly(sb) ||
+				reason == STOP_CP_REASON_SHUTDOWN) {
+		f2fs_warn(sbi, "Stopped filesystem due to readon: %d", reason);
 		return;
+	}
 
 	f2fs_warn(sbi, "Remounting filesystem read-only");
 	/*
-- 
2.44.0.478.gd926399ef9-goog