From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Takashi Iwai <tiwai@suse.de>, Hyeoncheol Lee <cheol.lee@lge.com>,
yjay.kim@lge.com, Sangseok Lee <sangseok.lee@lge.com>,
Hugh Dickins <hughd@google.com>,
"[4.7+]" <stable@vger.kernel.org>
Subject: Re: [PATCH v4 3/3] zram: support BDI_CAP_STABLE_WRITES
Date: Thu, 22 Dec 2016 10:31:34 +0900 [thread overview]
Message-ID: <20161222013134.GC644@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <1482366980-3782-4-git-send-email-minchan@kernel.org>
On (12/22/16 09:36), Minchan Kim wrote:
> zram has used per-cpu stream feature from v4.7.
> It aims for increasing cache hit ratio of scratch buffer for
> compressing. Downside of that approach is that zram should ask
> memory space for compressed page in per-cpu context which requires
> stricted gfp flag which could be failed. If so, it retries to
> allocate memory space out of per-cpu context so it could get memory
> this time and compress the data again, copies it to the memory space.
>
> In this scenario, zram assumes the data should never be changed
> but it is not true without stable page support. So, If the data is
> changed under us, zram can make buffer overrun so that zsmalloc
> free object chain is broken so system goes crash like below
> https://bugzilla.suse.com/show_bug.cgi?id=997574
>
> This patch adds BDI_CAP_STABLE_WRITES to zram for declaring
> "I am block device needing *stable write*".
>
> Fixes: da9556a2367c ("zram: user per-cpu compression streams")
> Cc: <stable@vger.kernel.org> [4.7+]
> Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
-ss
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prev parent reply other threads:[~2016-12-22 1:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-22 0:36 [PATCH v4 0/3] Fix zsmalloc crash problem Minchan Kim
2016-12-22 0:36 ` [PATCH v4 1/3] mm: support anonymous stable page Minchan Kim
2016-12-22 0:36 ` [PATCH v4 2/3] zram: revalidate disk under init_lock Minchan Kim
2016-12-22 1:32 ` Sergey Senozhatsky
2016-12-22 0:36 ` [PATCH v4 3/3] zram: support BDI_CAP_STABLE_WRITES Minchan Kim
2016-12-22 1:31 ` Sergey Senozhatsky [this message]
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