Re: [PATCH v2] xfs: handle register_shrinker error

Michal Hocko
2017-11-28T09:35:59Z

On Mon 27-11-17 09:44:53, Darrick J. Wong wrote:
[...]
> > From 1009db61988c48c9a9e327a9d076945b29b02eee Mon Sep 17 00:00:00 2001
> > From: Michal Hocko <mhocko@suse.com>
> > Date: Thu, 23 Nov 2017 17:13:40 +0100
> > Subject: [PATCH] xfs: fortify xfs_alloc_buftarg error handling
> >
> > percpu_counter_init failure path doesn't clean up &btp->bt_lru list.
> > Call list_lru_destroy in that error path. Similarly register_shrinker
> > error path is not handled.
> >
> > While it is unlikely to trigger these error path, it is not impossible
> > especially the later might fail with large NUMAs. Let's handle the
> > failure to make the code more robust.
> >
> > Acked-by: Dave Chinner <dchinner@redhat.com>
> > Noticed-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> > ---
> > fs/xfs/xfs_buf.c | 15 ++++++++++-----
> > 1 file changed, 10 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> > index 4db6e8d780f6..4c6e86d861fd 100644
> > --- a/fs/xfs/xfs_buf.c
> > +++ b/fs/xfs/xfs_buf.c
> > @@ -1815,22 +1815,27 @@ xfs_alloc_buftarg(
> > btp->bt_daxdev = dax_dev;
> >
> > if (xfs_setsize_buftarg_early(btp, bdev))
> > - goto error;
> > + goto error_free;
> >
> > if (list_lru_init(&btp->bt_lru))
> > - goto error;
> > + goto error_free;
> >
> > if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
> > - goto error;
> > + goto error_lru;
> >
> > btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
> > btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
> > btp->bt_shrinker.seeks = DEFAULT_SEEKS;
> > btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
> > - register_shrinker(&btp->bt_shrinker);
> > + if (register_shrinker(&btp->bt_shrinker))
> > + goto error_pcpu;
> > return btp;
> >
> > -error:
> > +error_pcpu:
> > + percpu_counter_destroy(&btp->bt_io_count);
> > +error_lru:
> > + list_lru_destroy(&btp->bt_lru);
> > +error_free:
> > kmem_free(btp);
> > return NULL;
>
> This part looks ok,
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

Are you going to apply the patch or should I re-send it with
acks/reviewed-by?
--
Michal Hocko
SUSE Labs