linux/drivers/staging/zram
Minchan Kim a0c516cbfc zram: don't grab mutex in zram_slot_free_noity
[1] introduced down_write in zram_slot_free_notify to prevent race
between zram_slot_free_notify and zram_bvec_[read|write]. The race
could happen if somebody who has right permission to open swap device
is reading swap device while it is used by swap in parallel.

However, zram_slot_free_notify is called with holding spin_lock of
swap layer so we shouldn't avoid holing mutex. Otherwise, lockdep
warns it.

This patch adds new list to handle free slot and workqueue
so zram_slot_free_notify just registers slot index to be freed and
registers the request to workqueue. If workqueue is expired,
it holds mutex_lock so there is no problem any more.

If any I/O is issued, zram handles pending slot-free request
caused by zram_slot_free_notify right before handling issued
request because workqueue wouldn't be expired yet so zram I/O
request handling function can miss it.

Lastly, when zram is reset, flush_work could handle all of pending
free request so we shouldn't have memory leak.

NOTE: If zram_slot_free_notify's kmalloc with GFP_ATOMIC would be
failed, the slot will be freed when next write I/O write the slot.

[1] [57ab0485, zram: use zram->lock to protect zram_free_page()
    in swap free notify path]

* from v2
  * refactoring

* from v1
  * totally redesign

Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-08-12 15:25:00 -07:00
..
Kconfig staging: Add angle bracket before and after the URL 2013-01-07 14:56:04 -08:00
Makefile zram: remove zram_sysfs file (v2) 2013-06-24 15:59:03 -07:00
zram.txt zram: force disksize setting before using zram 2013-02-03 17:52:49 -08:00
zram_drv.c zram: don't grab mutex in zram_slot_free_noity 2013-08-12 15:25:00 -07:00
zram_drv.h zram: don't grab mutex in zram_slot_free_noity 2013-08-12 15:25:00 -07:00