Re: [syzbot] INFO: task hung in ext4_fill_super

From: Pavel Skripkin <paskripkin@gmail.com>
To: syzbot <syzbot+c9ff4822a62eee994ea3@syzkaller.appspotmail.com>,
	adilger.kernel@dilger.ca, clang-built-linux@googlegroups.com,
	linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
	nathan@kernel.org, ndesaulniers@google.com,
	syzkaller-bugs@googlegroups.com, tytso@mit.edu
Subject: Re: [syzbot] INFO: task hung in ext4_fill_super
Date: Fri, 6 Aug 2021 10:45:32 +0300	[thread overview]
Message-ID: <daae3696-aed8-a0b6-9470-d76ab4901b7d@gmail.com> (raw)
In-Reply-To: <000000000000b6692805c8d0fae6@google.com>

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On 8/5/21 5:46 PM, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
> 
> Reported-and-tested-by: syzbot+c9ff4822a62eee994ea3@syzkaller.appspotmail.com
> 
> Tested on:
> 
> commit:         251a1524 Merge tag 'scsi-fixes' of git://git.kernel.or..
> git tree:       upstream
> kernel config:  https://syzkaller.appspot.com/x/.config?x=166c8f6532dd88df
> dashboard link: https://syzkaller.appspot.com/bug?extid=c9ff4822a62eee994ea3
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> patch:          https://syzkaller.appspot.com/x/patch.diff?x=160a3301300000
> 
> Note: testing is done by a robot and is best-effort only.
> 

#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master


With regards,
Pavel Skripkin

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From f31fdca900d687994a880dfd675d0a46da1eaec9 Mon Sep 17 00:00:00 2001
From: Pavel Skripkin <paskripkin@gmail.com>
Date: Fri, 6 Aug 2021 10:40:31 +0300
Subject: [PATCH] ext4: fix kthread_should_stop() while TASK_RUNNING

/* ... */

Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 fs/ext4/mmp.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index bc364c119af6..fd1985b79a8d 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -183,9 +183,15 @@ static int kmmpd(void *data)
 		}
 
 		diff = jiffies - last_update_time;
-		if (diff < mmp_update_interval * HZ)
-			schedule_timeout_interruptible(mmp_update_interval *
-						       HZ - diff);
+		if (diff < mmp_update_interval * HZ) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			if (kthread_should_stop()) {
+				__set_current_state(TASK_RUNNING);
+				break;
+			}
+
+			schedule_timeout(mmp_update_interval * HZ - diff);
+		}
 
 		/*
 		 * We need to make sure that more than mmp_check_interval
-- 
2.32.0

