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From: Ming Lei <ming.lei@redhat.com>
To: Shakeel Butt <shakeelb@google.com>
Cc: Roman Gushchin <guro@fb.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: Sat, 26 Sep 2020 09:43:25 +0800	[thread overview]
Message-ID: <20200926014325.GA2516054@T590> (raw)
In-Reply-To: <20200925191902.543953-1-shakeelb@google.com>

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>

Thanks,
Ming


  parent reply	other threads:[~2020-09-26  1:43 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 [this message]
2020-09-26  6:42                                                           ` Roman Gushchin
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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