Minchan Kim b09ab054b6 zram: support BDI_CAP_STABLE_WRITES ... 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: da9556a236 ("zram: user per-cpu compression streams") Link: http://lkml.kernel.org/r/1482366980-3782-4-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Takashi Iwai <tiwai@suse.de> Cc: Hyeoncheol Lee <cheol.lee@lge.com> Cc: <yjay.kim@lge.com> Cc: Sangseok Lee <sangseok.lee@lge.com> Cc: Hugh Dickins <hughd@google.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: <stable@vger.kernel.org> [4.7+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2017-01-10 18:31:55 -08:00
..
Kconfig	zram: delete custom lzo/lz4	2016-07-26 16:19:19 -07:00
Makefile	zram: delete custom lzo/lz4	2016-07-26 16:19:19 -07:00
zcomp.c	zram: Convert to hotplug state machine	2016-12-02 00:52:39 +01:00
zcomp.h	zram: Convert to hotplug state machine	2016-12-02 00:52:39 +01:00
zram_drv.c	zram: support BDI_CAP_STABLE_WRITES	2017-01-10 18:31:55 -08:00
zram_drv.h	zram: use crypto api to check alg availability	2016-07-26 16:19:19 -07:00