Re: [BUG 4.10-rc7] sb_fdblocks inconsistency in xfs/297 test

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On Mon, Feb 20, 2017 at 03:25:21PM +0100, Michal Hocko wrote:
> I have discussed that shortly with Jack and he suspects that xfs
> specific part of the iomap callbacks doesn't cancel reservations.
> Let's CC more xfs people. The thread starts
> http://lkml.kernel.org/r/20170210035348.GA7075@xxxxxxxxxxxxxxxxxxxxxxxx
> 

Have you tried commit fa7f138 ("xfs: clear delalloc and cache on buffered
write failure"), currently in for-next?

Brian

> On Fri 10-02-17 10:31:31, Michal Hocko wrote:
> > [CC Christoph]
> > 
> > On Fri 10-02-17 09:02:10, Michal Hocko wrote:
> > > On Fri 10-02-17 08:14:18, Michal Hocko wrote:
> > > > On Fri 10-02-17 11:53:48, Eryu Guan wrote:
> > > > > Hi,
> > > > > 
> > > > > I was testing 4.10-rc7 kernel and noticed that xfs_repair reported XFS
> > > > > corruption after fstests xfs/297 test. This didn't happen with 4.10-rc6
> > > > > kernel, and git bisect pointed the first bad commit to
> > > > > 
> > > > > commit d1908f52557b3230fbd63c0429f3b4b748bf2b6d
> > > > > Author: Michal Hocko <mhocko@xxxxxxxx>
> > > > > Date:   Fri Feb 3 13:13:26 2017 -0800
> > > > > 
> > > > >     fs: break out of iomap_file_buffered_write on fatal signals
> > > > > 
> > > > >     Tetsuo has noticed that an OOM stress test which performs large write
> > > > >     requests can cause the full memory reserves depletion.  He has tracked
> > > > >     this down to the following path
> > > > > ....
> > > > > 
> > > > > It's the sb_fdblocks field reports inconsistency:
> > > > > ...
> > > > > Phase 2 - using internal log   
> > > > >         - zero log...
> > > > >         - scan filesystem freespace and inode maps...
> > > > > sb_fdblocks 3367765, counted 3367863
> > > > >         - 11:37:41: scanning filesystem freespace - 16 of 16 allocation groups done
> > > > >         - found root inode chunk
> > > > > ...
> > > > > 
> > > > > And it can be reproduced almost 100% with all XFS test configurations
> > > > > (e.g. xfs_4k xfs_2k_reflink), on all test hosts I tried (so I didn't
> > > > > bother pasting my detailed test and host configs, if more info is needed
> > > > > please let me know).
> > > > 
> > > > The patch can lead to short writes when the task is killed. Was there
> > > > any OOM killer triggered during the test? If not who is killing the
> > > > task? I will try to reproduce later today.
> > > 
> > > I have checked both tests and they are killing the test but none of them
> > > seems to be using SIGKILL. The patch should make a difference only for
> > > fatal signal (aka SIGKILL). Is there any other part that can do SIGKILL
> > > except for the OOM killer?
> > 
> > I have done
> > diff --git a/fs/dax.c b/fs/dax.c
> > index c45598b912e1..4de00ceaf73d 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -1032,6 +1032,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> >  		ssize_t map_len;
> >  
> >  		if (fatal_signal_pending(current)) {
> > +			WARN(1, "dax_iomap_actor\n");
> >  			ret = -EINTR;
> >  			break;
> >  		}
> > diff --git a/fs/iomap.c b/fs/iomap.c
> > index a51cb4c07d4d..00019e2cdad3 100644
> > --- a/fs/iomap.c
> > +++ b/fs/iomap.c
> > @@ -114,8 +114,10 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> >  
> >  	BUG_ON(pos + len > iomap->offset + iomap->length);
> >  
> > -	if (fatal_signal_pending(current))
> > +	if (fatal_signal_pending(current)) {
> > +		WARN(1, "iomap_write_begin\n");
> >  		return -EINTR;
> > +	}
> >  
> >  	page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
> >  	if (!page)
> > 
> > and it triggered
> > [  135.055682] WARNING: CPU: 2 PID: 4894 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.087297] WARNING: CPU: 1 PID: 4899 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.150542] WARNING: CPU: 2 PID: 4857 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.153653] WARNING: CPU: 3 PID: 4889 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.154413] WARNING: CPU: 0 PID: 4929 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.154734] WARNING: CPU: 3 PID: 4934 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.162743] WARNING: CPU: 0 PID: 4813 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.163282] WARNING: CPU: 1 PID: 4891 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.163820] WARNING: CPU: 0 PID: 4932 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.169112] WARNING: CPU: 0 PID: 4923 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.182816] WARNING: CPU: 0 PID: 4892 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.321991] WARNING: CPU: 3 PID: 4872 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > 
> > always from
> > [  135.055682] WARNING: CPU: 2 PID: 4894 at fs/iomap.c:118 iomap_write_begin+0x72/0x12c
> > [  135.057092] iomap_write_begin
> > [  135.057556] Modules linked in: xfs libcrc32c
> > [  135.058191] CPU: 2 PID: 4894 Comm: fsstress Tainted: G        W       4.10.0-rc6-test1-00149-gd1908f52557b-dirty #1064
> > [  135.060349] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-1 04/01/2014
> > [  135.060865] Call Trace:
> > [  135.060865]  dump_stack+0x68/0x92
> > [  135.060865]  __warn+0xc2/0xdd
> > [  135.060865]  warn_slowpath_fmt+0x4b/0x53
> > [  135.060865]  iomap_write_begin+0x72/0x12c
> > [  135.060865]  iomap_write_actor+0x99/0x161
> > [  135.060865]  iomap_apply+0x9e/0xec
> > [  135.060865]  ? iomap_write_end+0x62/0x62
> > [  135.060865]  iomap_file_buffered_write+0x5b/0x7f
> > [  135.060865]  ? iomap_write_end+0x62/0x62
> > [  135.060865]  xfs_file_buffered_aio_write+0x187/0x2b4 [xfs]
> > [  135.060865]  xfs_file_write_iter+0x93/0x11c [xfs]
> > [  135.060865]  __vfs_write+0xcc/0xf5
> > [  135.060865]  vfs_write+0x100/0x1a9
> > [  135.060865]  SyS_write+0x51/0x8e
> > 
> > So somebody had to send SIGKILL to fsstress. Anyway, I am wondering
> > whether this is really a regression. xfs_file_buffered_aio_write used to
> > call generic_perform_write which does the same thing.
> > -- 
> > Michal Hocko
> > SUSE Labs
> 
> -- 
> Michal Hocko
> SUSE Labs
> --
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