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

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Date: Fri, 26 Apr 2024 08:18:44 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
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 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?

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
> 
>