linux-ext4 - Re: [PATCH] ext4: fix ext4_flush_completed

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Message-ID: <87a9w1ax91.fsf@openvz.org>
Date:	Fri, 05 Oct 2012 17:01:30 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, jack@...e.cz
Subject: Re: [PATCH] ext4: fix ext4_flush_completed_IO wait semantics

On Fri, 5 Oct 2012 08:40:27 -0400, Theodore Ts'o <tytso@....edu> wrote:
> On Wed, Oct 03, 2012 at 10:43:27PM +0400, Dmitry Monakhov wrote:
> > -int ext4_flush_completed_IO(struct inode *inode)
> > +int ext4_flush_unwritten_io(struct inode *inode)
> >  {
> > -	return ext4_do_flush_completed_IO(inode, NULL);
> > +	int ret;
> > +	WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
> > +	ret = ext4_do_flush_completed_IO(inode, NULL);
> > +	ext4_unwritten_wait(inode);
> > +	return ret;
> >  }
> >  
> 
> This WARN_ON is triggering on the truncate path...
Yeap, this is false positive one. We skip i_mutex on ext4_evict_inode
This is strange xfsstress 269'th should caught that for me.
I'll try to prepare workaround ASAP.
> 
> ------------[ cut here ]------------
> WARNING: at /usr/projects/linux/ext4/fs/ext4/page-io.c:232 ext4_flush_unwritten_io+0x2d/0x4c()
> Hardware name: Bochs
> Modules linked in:
> Pid: 1907, comm: findfs Not tainted 3.6.0-rc1-00071-gb1edc6d #441
> Call Trace:
>  [<c0159cb3>] warn_slowpath_common+0x68/0x7d
>  [<c0272ebd>] ? ext4_flush_unwritten_io+0x2d/0x4c
>  [<c0159cdc>] warn_slowpath_null+0x14/0x18
>  [<c0272ebd>] ext4_flush_unwritten_io+0x2d/0x4c
>  [<c028fa09>] ext4_ext_truncate+0x21/0x174
>  [<c0270cbb>] ? ext4_mark_inode_dirty+0x172/0x1a9
>  [<c026ed9e>] ext4_truncate+0x7b/0xb9
>  [<c0272414>] ext4_evict_inode+0x1ec/0x2e3
>  [<c021a724>] evict+0x94/0x135
>  [<c021a939>] iput+0x174/0x17a
>  [<c02122bd>] do_unlinkat+0xc8/0x106
>  [<c06d8b5e>] ? restore_all+0xf/0xf
>  [<c0199909>] ? trace_hardirqs_on_caller+0x103/0x154
>  [<c02138f0>] sys_unlink+0x15/0x17
>  [<c06d8b25>] syscall_call+0x7/0xb
> ---[ end trace cdd8306e94494df8 ]---
> 
> 							- Ted
> 
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