linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: ensure node page reads complete before f2fs_put

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Message-ID: <aPEvpeM_cXWcxcZe@google.com>
Date: Thu, 16 Oct 2025 17:47:17 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao@...nel.org>
Cc: Jan Prusakowski <jprusakowski@...gle.com>, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: ensure node page reads complete before
 f2fs_put_super() finishes

On 10/11, Chao Yu wrote:
> On 10/11/25 00:02, Jaegeuk Kim wrote:
> > On 10/09, Chao Yu wrote:
> >> On 10/6/2025 4:46 PM, Jan Prusakowski via Linux-f2fs-devel wrote:
> >>> Xfstests generic/335, generic/336 sometimes crash with the following message:
> >>>
> >>> F2FS-fs (dm-0): detect filesystem reference count leak during umount, type: 9, count: 1
> >>> ------------[ cut here ]------------
> >>> kernel BUG at fs/f2fs/super.c:1939!
> >>> Oops: invalid opcode: 0000 [#1] SMP NOPTI
> >>> CPU: 1 UID: 0 PID: 609351 Comm: umount Tainted: G        W           6.17.0-rc5-xfstests-g9dd1835ecda5 #1 PREEMPT(none)
> >>> Tainted: [W]=WARN
> >>> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> >>> RIP: 0010:f2fs_put_super+0x3b3/0x3c0
> >>> Call Trace:
> >>>   <TASK>
> >>>   generic_shutdown_super+0x7e/0x190
> >>>   kill_block_super+0x1a/0x40
> >>>   kill_f2fs_super+0x9d/0x190
> >>>   deactivate_locked_super+0x30/0xb0
> >>>   cleanup_mnt+0xba/0x150
> >>>   task_work_run+0x5c/0xa0
> >>>   exit_to_user_mode_loop+0xb7/0xc0
> >>>   do_syscall_64+0x1ae/0x1c0
> >>>   entry_SYSCALL_64_after_hwframe+0x76/0x7e
> >>>   </TASK>
> >>> ---[ end trace 0000000000000000 ]---
> >>>
> >>> It appears that sometimes it is possible that f2fs_put_super() is called before
> >>> all node page reads are completed.
> >>> Adding a call to f2fs_wait_on_all_pages() for F2FS_RD_NODE fixes the problem.
> >>>
> >>> Fixes: bf22c3cc8ce7 ("f2fs: fix the panic in do_checkpoint()")
> >>>
> >>> Signed-off-by: Jan Prusakowski <jprusakowski@...gle.com>
> >>> ---
> >>>   fs/f2fs/super.c | 1 +
> >>>   1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> >>> index 1e0678e37a30..5c94bc42b8a1 100644
> >>> --- a/fs/f2fs/super.c
> >>> +++ b/fs/f2fs/super.c
> >>> @@ -1976,6 +1976,7 @@ static void f2fs_put_super(struct super_block *sb)
> >>>   	f2fs_flush_merged_writes(sbi);
> >>>   	f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA);
> >>> +	f2fs_wait_on_all_pages(sbi, F2FS_RD_NODE);
> >>
> >> Jan,
> >>
> >> At this stage, GC and checkpoint are both stopped, why there is still read
> >> IOs on node page? Who is reading node page? Can you please dig more details
> >> for this issue?
> > 
> > We don't actually wait for completing read IOs. So, I think it doesn't matter
> > the threads are stopped?
> 
> Read on node page should be synchronous? so if the threads are stopped, there
> should be no node IOs? Oh, Or there is still pending asynchronous readahead IO
> on node page after all threads are stopped?

I remember we submit IOs and wait for its completion when we need by lock_page.

> 
> Thanks,
> 
> > 
> >>
> >> Thanks,
> >>
> >>>   	if (err || f2fs_cp_error(sbi)) {
> >>>   		truncate_inode_pages_final(NODE_MAPPING(sbi));