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

Pankaj Raghav (Samsung)
2024-04-28T21:06:42Z

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@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-by: Dave Chinner <dchinner@redhat.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@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);
> > --
> > 2.34.1
> >
> >