From: Roman Gushchin <guro@fb.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Theodore Y . Ts'o" <tytso@mit.edu>, Jens Axboe <axboe@kernel.dk>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
Vlastimil Babka <vbabka@suse.cz>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: REGRESSION: 37f4a24c2469: blk-mq: centralise related handling into blk_mq_get_driver_tag
Date: Fri, 25 Sep 2020 23:42:32 -0700 [thread overview]
Message-ID: <20200926064232.GA2240876@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20200926014325.GA2516054@T590>
On Sat, Sep 26, 2020 at 09:43:25AM +0800, Ming Lei wrote:
> On Fri, Sep 25, 2020 at 12:19:02PM -0700, Shakeel Butt wrote:
> > On Fri, Sep 25, 2020 at 10:58 AM Shakeel Butt <shakeelb@google.com>
> > wrote:
> > >
> > [snip]
> > >
> > > I don't think you can ignore the flushing. The __free_once() in
> > > ___cache_free() assumes there is a space available.
> > >
> > > BTW do_drain() also have the same issue.
> > >
> > > Why not move slabs_destroy() after we update ac->avail and memmove()?
> >
> > Ming, can you please try the following patch?
> >
> >
> > From: Shakeel Butt <shakeelb@google.com>
> >
> > [PATCH] mm: slab: fix potential infinite recursion in ___cache_free
> >
> > With the commit 10befea91b61 ("mm: memcg/slab: use a single set of
> > kmem_caches for all allocations"), it becomes possible to call kfree()
> > from the slabs_destroy(). However if slabs_destroy() is being called for
> > the array_cache of the local CPU then this opens the potential scenario
> > of infinite recursion because kfree() called from slabs_destroy() can
> > call slabs_destroy() with the same array_cache of the local CPU. Since
> > the array_cache of the local CPU is not updated before calling
> > slabs_destroy(), it will try to free the same pages.
> >
> > To fix the issue, simply update the cache before calling
> > slabs_destroy().
> >
> > Signed-off-by: Shakeel Butt <shakeelb@google.com>
> > ---
> > mm/slab.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/slab.c b/mm/slab.c
> > index 3160dff6fd76..f658e86ec8ce 100644
> > --- a/mm/slab.c
> > +++ b/mm/slab.c
> > @@ -1632,6 +1632,10 @@ static void slab_destroy(struct kmem_cache *cachep, struct page *page)
> > kmem_cache_free(cachep->freelist_cache, freelist);
> > }
> >
> > +/*
> > + * Update the size of the caches before calling slabs_destroy as it may
> > + * recursively call kfree.
> > + */
> > static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list)
> > {
> > struct page *page, *n;
> > @@ -2153,8 +2157,8 @@ static void do_drain(void *arg)
> > spin_lock(&n->list_lock);
> > free_block(cachep, ac->entry, ac->avail, node, &list);
> > spin_unlock(&n->list_lock);
> > - slabs_destroy(cachep, &list);
> > ac->avail = 0;
> > + slabs_destroy(cachep, &list);
> > }
> >
> > static void drain_cpu_caches(struct kmem_cache *cachep)
> > @@ -3402,9 +3406,9 @@ static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)
> > }
> > #endif
> > spin_unlock(&n->list_lock);
> > - slabs_destroy(cachep, &list);
> > ac->avail -= batchcount;
> > memmove(ac->entry, &(ac->entry[batchcount]), sizeof(void *)*ac->avail);
> > + slabs_destroy(cachep, &list);
> > }
>
> The issue can't be reproduced after applying this patch:
>
> Tested-by: Ming Lei <ming.lei@redhat.com>
Perfect, thank you very much for the confirmation!
Shakeel, can you, please, resend the patch with the proper fixes tag
and the updated commit log? Please, feel free to add
Reviewed-by: Roman Gushchin <guro@fb.com> .
Thank you!
Roman
next prev parent reply other threads:[~2020-09-26 6:43 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 23:02 [PATCH] ext4: flag as supporting buffered async reads Jens Axboe
2020-08-11 14:31 ` Jens Axboe
2020-08-18 18:11 ` Theodore Y. Ts'o
2020-08-18 18:12 ` Jens Axboe
2020-08-21 21:26 ` Jens Axboe
2020-08-22 14:33 ` Theodore Y. Ts'o
2020-08-22 15:48 ` Jens Axboe
2020-08-24 10:56 ` Jens Axboe
2020-08-25 14:18 ` Jens Axboe
2020-08-27 1:54 ` Jens Axboe
2020-09-04 0:10 ` Jens Axboe
2020-09-04 3:55 ` Theodore Y. Ts'o
2020-09-04 14:51 ` Jens Axboe
2020-09-04 15:25 ` Darrick J. Wong
2020-09-15 4:45 ` REGRESSION: 37f4a24c2469: blk-mq: centralise related handling into blk_mq_get_driver_tag Theodore Y. Ts'o
2020-09-15 7:33 ` Ming Lei
2020-09-15 22:45 ` Theodore Y. Ts'o
2020-09-15 23:09 ` Ming Lei
2020-09-16 20:20 ` Theodore Y. Ts'o
2020-09-17 2:20 ` Ming Lei
2020-09-17 14:30 ` Theodore Y. Ts'o
2020-09-17 23:08 ` Ming Lei
2020-09-24 0:59 ` Ming Lei
2020-09-24 14:33 ` Theodore Y. Ts'o
2020-09-25 1:13 ` Theodore Y. Ts'o
2020-09-25 7:31 ` Ming Lei
2020-09-25 16:19 ` Ming Lei
2020-09-25 16:32 ` Shakeel Butt
2020-09-25 16:47 ` Shakeel Butt
2020-09-25 17:22 ` Roman Gushchin
2020-09-25 17:17 ` Linus Torvalds
2020-09-25 17:22 ` Shakeel Butt
2020-09-25 17:35 ` Shakeel Butt
2020-09-25 17:47 ` Roman Gushchin
2020-09-25 17:58 ` Shakeel Butt
2020-09-25 19:19 ` Shakeel Butt
2020-09-25 20:56 ` Roman Gushchin
2020-09-25 21:18 ` Shakeel Butt
2020-09-27 17:38 ` Theodore Y. Ts'o
2020-09-26 1:43 ` Ming Lei
2020-09-26 6:42 ` Roman Gushchin [this message]
2020-09-25 1:14 ` Ming Lei
2020-09-25 2:34 ` Ming Lei
2020-10-02 20:08 ` [PATCH] ext4: flag as supporting buffered async reads Theodore Y. Ts'o
2020-10-02 20:10 ` Jens Axboe
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