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From: Andrew Morton <akpm@linux-foundation.org>
To: Christopher Lameter <cl@linux.com>
Cc: Yu Zhao <yuzhao@google.com>, Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [FIX] slub: Remove kmalloc under list_lock from list_slab_objects() V2
Date: Sat, 30 Nov 2019 15:09:08 -0800
Message-ID: <20191130150908.06b2646edfa7bdc12a943c25@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.21.1911111553020.15366@www.lameter.com>

On Mon, 11 Nov 2019 15:55:05 +0000 (UTC) Christopher Lameter <cl@linux.com> wrote:

> Regardless of the issue with memcgs allowing allocations from its
> kmalloc array during shutdown: This patch cleans things up and properly
> allocates the bitmap outside of the list_lock.
> 
> 
> [FIX] slub: Remove kmalloc under list_lock from list_slab_objects() V2
> 
> V1->V2 : Properly handle CONFIG_SLUB_DEBUG. Handle bitmap free correctly.
> 
> list_slab_objects() is called when a slab is destroyed and there are objects still left
> to list the objects in the syslog. This is a pretty rare event.
> 
> And there it seems we take the list_lock and call kmalloc while holding that lock.
> 
> Perform the allocation in free_partial() before the list_lock is taken.

No response here?  It looks a lot simpler than the originally proposed
patch?

> --- linux.orig/mm/slub.c	2019-10-15 13:54:57.032655296 +0000
> +++ linux/mm/slub.c	2019-11-11 15:52:11.616397853 +0000
> @@ -3690,14 +3690,15 @@ error:
>  }
> 
>  static void list_slab_objects(struct kmem_cache *s, struct page *page,
> -							const char *text)
> +					const char *text, unsigned long *map)
>  {
>  #ifdef CONFIG_SLUB_DEBUG
>  	void *addr = page_address(page);
>  	void *p;
> -	unsigned long *map = bitmap_zalloc(page->objects, GFP_ATOMIC);
> +
>  	if (!map)
>  		return;
> +
>  	slab_err(s, page, text, s->name);
>  	slab_lock(page);
> 
> @@ -3710,7 +3711,6 @@ static void list_slab_objects(struct kme
>  		}
>  	}
>  	slab_unlock(page);
> -	bitmap_free(map);
>  #endif
>  }
> 
> @@ -3723,6 +3723,11 @@ static void free_partial(struct kmem_cac
>  {
>  	LIST_HEAD(discard);
>  	struct page *page, *h;
> +	unsigned long *map = NULL;
> +
> +#ifdef CONFIG_SLUB_DEBUG
> +	map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL);
> +#endif
> 
>  	BUG_ON(irqs_disabled());
>  	spin_lock_irq(&n->list_lock);
> @@ -3732,11 +3737,16 @@ static void free_partial(struct kmem_cac
>  			list_add(&page->slab_list, &discard);
>  		} else {
>  			list_slab_objects(s, page,
> -			"Objects remaining in %s on __kmem_cache_shutdown()");
> +			"Objects remaining in %s on __kmem_cache_shutdown()",
> +			map);
>  		}
>  	}
>  	spin_unlock_irq(&n->list_lock);
> 
> +#ifdef CONFIG_SLUB_DEBUG
> +	bitmap_free(map);
> +#endif
> +
>  	list_for_each_entry_safe(page, h, &discard, slab_list)
>  		discard_slab(s, page);
>  }


  reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09  6:10 [PATCH] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-09 16:00 ` Kirill A. Shutemov
     [not found]   ` <e5e25aa3-651d-92b4-ac82-c5011c66a7cb@I-love.SAKURA.ne.jp>
2019-09-09 21:39     ` Yu Zhao
     [not found]       ` <201909100141.x8A1fVdu048305@www262.sakura.ne.jp>
2019-09-10  2:16         ` Yu Zhao
2019-09-10  9:16       ` Kirill A. Shutemov
2019-09-11 14:13 ` Andrew Morton
2019-09-12  0:29   ` [PATCH 1/3] mm: correct mask size for slub page->objects Yu Zhao
2019-09-12  0:29     ` [PATCH 2/3] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12  0:44       ` Kirill A. Shutemov
2019-09-12  1:31         ` Yu Zhao
2019-09-12  2:31         ` [PATCH v2 1/4] mm: correct mask size for slub page->objects Yu Zhao
2019-09-12  2:31           ` [PATCH v2 2/4] mm: clean up validate_slab() Yu Zhao
2019-09-12  9:46             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 3/4] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12 10:04             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 4/4] mm: lock slub page when listing objects Yu Zhao
2019-09-12 10:06             ` Kirill A. Shutemov
2019-09-12 21:12               ` Yu Zhao
2019-09-13 14:58             ` Christopher Lameter
2019-09-12  9:40           ` [PATCH v2 1/4] mm: correct mask size for slub page->objects Kirill A. Shutemov
2019-09-12 21:11             ` Yu Zhao
2019-09-12 22:03               ` Kirill A. Shutemov
2019-09-14  0:07           ` [PATCH v3 1/2] mm: clean up validate_slab() Yu Zhao
2019-09-14  0:07             ` [PATCH v3 2/2] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-16  8:39             ` [PATCH v3 1/2] mm: clean up validate_slab() Kirill A. Shutemov
2019-11-08 19:39             ` [PATCH v4 " Yu Zhao
2019-11-08 19:39               ` [PATCH v4 2/2] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-11-09 20:52                 ` Christopher Lameter
2019-11-09 23:01                   ` Yu Zhao
2019-11-09 23:16                     ` Christopher Lameter
2019-11-10 18:47                       ` Yu Zhao
2019-11-11 15:47                         ` Christopher Lameter
2019-11-11 15:55                           ` [FIX] slub: Remove kmalloc under list_lock from list_slab_objects() V2 Christopher Lameter
2019-11-30 23:09                             ` Andrew Morton [this message]
2019-12-02 15:12                               ` Christopher Lameter
2019-12-07 22:03                                 ` Yu Zhao
2020-01-10 14:11                                   ` Vlastimil Babka
     [not found]                                     ` <e0ed44ae-8dae-e8db-9d14-2b09b239af8e@i-love.sakura.ne.jp>
2020-01-13  1:34                                       ` Christopher Lameter
2019-11-11 18:15                           ` [PATCH v4 2/2] mm: avoid slub allocation while holding list_lock Shakeel Butt
2019-09-12  0:29     ` [PATCH 3/3] mm: lock slub page when listing objects Yu Zhao

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