Re: [PATCH 1/4] xfs: use kvmalloc for xattr buffers

Darrick J. Wong
2024-04-03T03:43:43Z

On Wed, Apr 03, 2024 at 08:38:16AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.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@pankajraghav.com>
> Fixes: f078d4ea8276 ("xfs: convert kmem_alloc() to kmalloc()")
> Signed-off-be: Dave Chinner <dchinner@redhat.com>

Looks fine to me,
Reviewed-by: Darrick J. Wong <djwong@kernel.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);
> --
> 2.43.0
>
>