linux-kernel - Re: [PATCH] xfs: add __GFP_NOLOCKDEP when allocating memory in xfs_attr_shortform

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Date: Fri, 28 Jun 2024 10:01:18 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Eric Sandeen <sandeen@...deen.net>
Cc: Jiwei Sun <sunjw10@...look.com>, chandan.babu@...cle.com,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	sunjw10@...ovo.com, ahuang12@...ovo.com, yi.zhang@...hat.com
Subject: Re: [PATCH] xfs: add __GFP_NOLOCKDEP when allocating memory in
 xfs_attr_shortform_list()

On Fri, Jun 28, 2024 at 11:25:10AM -0500, Eric Sandeen wrote:
> On 6/27/24 8:12 AM, Jiwei Sun wrote:
> > From: Jiwei Sun <sunjw10@...ovo.com>
> > 
> > If the following configuration is set
> > CONFIG_LOCKDEP=y
> > 
> > The following warning log appears,
> 
> Was just about to send this. :)
> 
> I had talked to dchinner about this and he also suggested that this was 
> missed in the series that removed GFP_NOFS, i.e.
> 
> [PATCH 00/12] xfs: remove remaining kmem interfaces and GFP_NOFS usage
> at https://lore.kernel.org/linux-mm/20240622094411.GA830005@ceph-admin/T/
> 
> So, I think this could also use one or both of:
> 
> Fixes: 204fae32d5f7 ("xfs: clean up remaining GFP_NOFS users")
> Fixes: 94a69db2367e ("xfs: use __GFP_NOLOCKDEP instead of GFP_NOFS")
> 
> ...
> 
> > This is a false positive. If a node is getting reclaimed, it cannot be
> > the target of a flistxattr operation. Commit 6dcde60efd94 ("xfs: more
> > lockdep whackamole with kmem_alloc*") has the similar root cause.
> > 
> > Fix the issue by adding __GFP_NOLOCKDEP in order to shut up lockdep.
> > 
> > Signed-off-by: Jiwei Sun <sunjw10@...ovo.com>
> > Suggested-by: Adrian Huang <ahuang12@...ovo.com>
> > ---
> >  fs/xfs/xfs_attr_list.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
> > index 5c947e5ce8b8..506ade0befa4 100644
> > --- a/fs/xfs/xfs_attr_list.c
> > +++ b/fs/xfs/xfs_attr_list.c
> > @@ -114,7 +114,8 @@ xfs_attr_shortform_list(
> >  	 * It didn't all fit, so we have to sort everything on hashval.
> >  	 */
> >  	sbsize = sf->count * sizeof(*sbuf);
> > -	sbp = sbuf = kmalloc(sbsize, GFP_KERNEL | __GFP_NOFAIL);
> > +	sbp = sbuf = kmalloc(sbsize, GFP_KERNEL | __GFP_NOFAIL |
> > +			     __GFP_NOLOCKDEP);
> 
> Minor nitpick, style-wise we seem to do:
> 
>         sbp = sbuf = kmalloc(sbsize,
>                         GFP_KERNEL | __GFP_NOLOCKDEP | __GFP_NOFAIL);
> 
> in most other places, and not split the flags onto 2 lines, since you need
> to add a line anyway.
> 
> Otherwise,
> 
> Acked-by: Eric Sandeen <sandeen@...hat.com>

Hey, could you all please read the list before sending duplicate
patches?

https://lore.kernel.org/linux-xfs/20240622082631.2661148-1-leo.lilong@huawei.com/

--D

> >  	/*
> >  	 * Scan the attribute list for the rest of the entries, storing
> 
>