linux-kernel - Re: [PATCH v4 08/11] xfs: use kvmalloc for xattr buffers

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Message-ID: <20240428210634.bkarwrwi6rdr6ywx@quentin>
Date: Sun, 28 Apr 2024 21:06:34 +0000
From: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: willy@...radead.org, brauner@...nel.org, david@...morbit.com,
	chandan.babu@...cle.com, akpm@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, hare@...e.de,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-xfs@...r.kernel.org, mcgrof@...nel.org, gost.dev@...sung.com,
	p.raghav@...sung.com, Dave Chinner <dchinner@...hat.com>
Subject: Re: [PATCH v4 08/11] xfs: use kvmalloc for xattr buffers

On Fri, Apr 26, 2024 at 08:18:44AM -0700, Darrick J. Wong wrote:
> On Thu, Apr 25, 2024 at 01:37:43PM +0200, Pankaj Raghav (Samsung) wrote:
> > From: Dave Chinner <dchinner@...hat.com>
> > 
> > Pankaj Raghav reported that when filesystem block size is larger
> > than page size, the xattr code can use kmalloc() for high order
> > allocations. This triggers a useless warning in the allocator as it
> > is a __GFP_NOFAIL allocation here:
> > 
> > static inline
> > struct page *rmqueue(struct zone *preferred_zone,
> >                         struct zone *zone, unsigned int order,
> >                         gfp_t gfp_flags, unsigned int alloc_flags,
> >                         int migratetype)
> > {
> >         struct page *page;
> > 
> >         /*
> >          * We most definitely don't want callers attempting to
> >          * allocate greater than order-1 page units with __GFP_NOFAIL.
> >          */
> > >>>>    WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
> > ...
> > 
> > Fix this by changing all these call sites to use kvmalloc(), which
> > will strip the NOFAIL from the kmalloc attempt and if that fails
> > will do a __GFP_NOFAIL vmalloc().
> > 
> > This is not an issue that productions systems will see as
> > filesystems with block size > page size cannot be mounted by the
> > kernel; Pankaj is developing this functionality right now.
> > 
> > Reported-by: Pankaj Raghav <kernel@...kajraghav.com>
> > Fixes: f078d4ea8276 ("xfs: convert kmem_alloc() to kmalloc()")
> > Signed-off-by: Dave Chinner <dchinner@...hat.com>
> 
> Didn't this already go in for-next?

I don't think so. I think Christoph suggested to have it in the LBS
series and see if MM folks can fix the issue upstream.[1]

[1] https://www.spinics.net/lists/linux-xfs/msg83130.html
> 
> If not,
> Reviewed-by: Darrick J. Wong <djwong@...nel.org>
> 
> --D
> 
> > ---
> >  fs/xfs/libxfs/xfs_attr_leaf.c | 15 ++++++---------
> >  1 file changed, 6 insertions(+), 9 deletions(-)
> > 
> > diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> > index ac904cc1a97b..969abc6efd70 100644
> > --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> > +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> > @@ -1059,10 +1059,7 @@ xfs_attr3_leaf_to_shortform(
> >  
> >  	trace_xfs_attr_leaf_to_sf(args);
> >  
> > -	tmpbuffer = kmalloc(args->geo->blksize, GFP_KERNEL | __GFP_NOFAIL);
> > -	if (!tmpbuffer)
> > -		return -ENOMEM;
> > -
> > +	tmpbuffer = kvmalloc(args->geo->blksize, GFP_KERNEL | __GFP_NOFAIL);
> >  	memcpy(tmpbuffer, bp->b_addr, args->geo->blksize);
> >  
> >  	leaf = (xfs_attr_leafblock_t *)tmpbuffer;
> > @@ -1125,7 +1122,7 @@ xfs_attr3_leaf_to_shortform(
> >  	error = 0;
> >  
> >  out:
> > -	kfree(tmpbuffer);
> > +	kvfree(tmpbuffer);
> >  	return error;
> >  }
> >  
> > @@ -1533,7 +1530,7 @@ xfs_attr3_leaf_compact(
> >  
> >  	trace_xfs_attr_leaf_compact(args);
> >  
> > -	tmpbuffer = kmalloc(args->geo->blksize, GFP_KERNEL | __GFP_NOFAIL);
> > +	tmpbuffer = kvmalloc(args->geo->blksize, GFP_KERNEL | __GFP_NOFAIL);
> >  	memcpy(tmpbuffer, bp->b_addr, args->geo->blksize);
> >  	memset(bp->b_addr, 0, args->geo->blksize);
> >  	leaf_src = (xfs_attr_leafblock_t *)tmpbuffer;
> > @@ -1571,7 +1568,7 @@ xfs_attr3_leaf_compact(
> >  	 */
> >  	xfs_trans_log_buf(trans, bp, 0, args->geo->blksize - 1);
> >  
> > -	kfree(tmpbuffer);
> > +	kvfree(tmpbuffer);
> >  }
> >  
> >  /*
> > @@ -2250,7 +2247,7 @@ xfs_attr3_leaf_unbalance(
> >  		struct xfs_attr_leafblock *tmp_leaf;
> >  		struct xfs_attr3_icleaf_hdr tmphdr;
> >  
> > -		tmp_leaf = kzalloc(state->args->geo->blksize,
> > +		tmp_leaf = kvzalloc(state->args->geo->blksize,
> >  				GFP_KERNEL | __GFP_NOFAIL);
> >  
> >  		/*
> > @@ -2291,7 +2288,7 @@ xfs_attr3_leaf_unbalance(
> >  		}
> >  		memcpy(save_leaf, tmp_leaf, state->args->geo->blksize);
> >  		savehdr = tmphdr; /* struct copy */
> > -		kfree(tmp_leaf);
> > +		kvfree(tmp_leaf);
> >  	}
> >  
> >  	xfs_attr3_leaf_hdr_to_disk(state->args->geo, save_leaf, &savehdr);
> > -- 
> > 2.34.1
> > 
> >