[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>
(cherry picked from commit a0c516cbfc)
Conflicts:
drivers/staging/zram/zram_drv.c
When system power up, hdmi irq will be enabled twice for
hwc will call fb unblack notifier. So if hdmi is not in suspend
mode, it is no need to call rk3036_hdmi_early_resume when fb unblank
event is triggered.
