Sergey Senozhatsky f405c445a4 zram: close race by open overriding ... [ Original patch from Minchan Kim <minchan@kernel.org> ] Commit ba6b17d68c ("zram: fix umount-reset_store-mount race condition") introduced bdev->bd_mutex to protect a race between mount and reset. At that time, we don't have dynamic zram-add/remove feature so it was okay. However, as we introduce dynamic device feature, bd_mutex became trouble. CPU 0 echo 1 > /sys/block/zram<id>/reset -> kernfs->s_active(A) -> zram:reset_store->bd_mutex(B) CPU 1 echo <id> > /sys/class/zram/zram-remove ->zram:zram_remove: bd_mutex(B) -> sysfs_remove_group -> kernfs->s_active(A) IOW, AB -> BA deadlock The reason we are holding bd_mutex for zram_remove is to prevent any incoming open /dev/zram[0-9]. Otherwise, we could remove zram others already have opened. But it causes above deadlock problem. To fix the problem, this patch overrides block_device.open and it returns -EBUSY if zram asserts he claims zram to reset so any incoming open will be failed so we don't need to hold bd_mutex for zram_remove ayn more. This patch is to prepare for zram-add/remove feature. [sergey.senozhatsky@gmail.com: simplify reset_store()] Signed-off-by: Minchan Kim <minchan@kernel.org> Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2015-06-25 17:00:36 -07:00
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Kconfig	zram: remove obsolete ZRAM_DEBUG option	2015-06-25 17:00:35 -07:00
Makefile	zram: add lz4 algorithm backend	2014-04-07 16:36:01 -07:00
zcomp_lz4.c	zram: add lz4 algorithm backend	2014-04-07 16:36:01 -07:00
zcomp_lz4.h	zram: add lz4 algorithm backend	2014-04-07 16:36:01 -07:00
zcomp_lzo.c	zram: introduce compressing backend abstraction	2014-04-07 16:36:01 -07:00
zcomp_lzo.h	zram: introduce compressing backend abstraction	2014-04-07 16:36:01 -07:00
zcomp.c	zram: use scnprintf() in attrs show() methods	2014-04-07 16:36:02 -07:00
zcomp.h	zram: propagate error to user	2014-04-07 16:36:02 -07:00
zram_drv.c	zram: close race by open overriding	2015-06-25 17:00:36 -07:00
zram_drv.h	zram: close race by open overriding	2015-06-25 17:00:36 -07:00