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Date: Tue, 9 Apr 2024 16:20:19 +0000
From: Jaegeuk Kim <jaegeuk@kernel.org>
To: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Cc: Light Hsieh =?utf-8?B?KOisneaYjueHiCk=?= <Light.Hsieh@mediatek.com>
Subject: Re: [PATCH v2] f2fs: don't set RO when shutting down f2fs
Message-ID: <ZhVqwwCesxWOfbOA@google.com>
References: <20240404195254.556896-1-jaegeuk@kernel.org>
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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@mediatek.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---

 Change log from v1:
  - use better variable
  - fix typo

 fs/f2fs/super.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 8ac4734c2df6..df32573d1f62 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4159,9 +4159,15 @@ 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) || shutdown) {
+		f2fs_warn(sbi, "Stopped filesystem due to reason: %d", reason);
 		return;
+	}
 
 	f2fs_warn(sbi, "Remounting filesystem read-only");
 	/*
-- 
2.44.0.478.gd926399ef9-goog