Piteball/android_kernel_google_msm
1
0
Fork 0
mirror of https://github.com/followmsi/android_kernel_google_msm.git synced 2024-11-06 23:17:41 +00:00
Code Issues Projects Releases Wiki Activity

UPSTREAM: zram: fix umount-reset_store-mount race condition

Browse source 
(cherry-pick from commit ba6b17d68c8e3aa8d55d0474299cb931965c5ea5)

Ganesh Mahendran was the first one who proposed to use bdev->bd_mutex to
avoid ->bd_holders race condition:

        CPU0                            CPU1
umount /* zram->init_done is true */
reset_store()
bdev->bd_holders == 0                   mount
...                                     zram_make_request()
zram_reset_device()

However, his solution required some considerable amount of code movement,
which we can avoid.

Apart from using bdev->bd_mutex in reset_store(), this patch also
simplifies zram_reset_device().

zram_reset_device() has a bool parameter reset_capacity which tells it
whether disk capacity and itself disk should be reset.  There are two
zram_reset_device() callers:

-- zram_exit() passes reset_capacity=false
-- reset_store() passes reset_capacity=true

So we can move reset_capacity-sensitive work out of zram_reset_device()
and perform it unconditionally in reset_store().  This also lets us drop
reset_capacity parameter from zram_reset_device() and pass zram pointer
only.

Bug: 25951511

Change-Id: I009e5303f133d60fb022fef9397863f823bd1e33
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sergey Senozhatsky 2015-02-12 15:00:36 -08:00 committed by Artem Borisov
parent f3f8a63d9e
commit 3814401b02
1 changed files with 9 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

23
drivers/block/zram/zram_drv.c
View file

@ -716,7 +716,7 @@ static void zram_bio_discard(struct zram *zram, u32 index,
} }
} }
static void zram_reset_device(struct zram *zram, bool reset_capacity) static void zram_reset_device(struct zram *zram)
{ {
down_write(&zram->init_lock); down_write(&zram->init_lock);
@ -735,18 +735,7 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
memset(&zram->stats, 0, sizeof(zram->stats)); memset(&zram->stats, 0, sizeof(zram->stats));
zram->disksize = 0; zram->disksize = 0;
if (reset_capacity)
set_capacity(zram->disk, 0);
up_write(&zram->init_lock); up_write(&zram->init_lock);
/*
* Revalidate disk out of the init_lock to avoid lockdep splat.
* It's okay because disk's capacity is protected by init_lock
* so that revalidate_disk always sees up-to-date capacity.
*/
if (reset_capacity)
revalidate_disk(zram->disk);
} }
static ssize_t disksize_store(struct device *dev, static ssize_t disksize_store(struct device *dev,
@ -819,6 +808,7 @@ static ssize_t reset_store(struct device *dev,
if (!bdev) if (!bdev)
return -ENOMEM; return -ENOMEM;
mutex_lock(&bdev->bd_mutex);
/* Do not reset an active device! */ /* Do not reset an active device! */
if (bdev->bd_holders) { if (bdev->bd_holders) {
ret = -EBUSY; ret = -EBUSY;
@ -836,12 +826,17 @@ static ssize_t reset_store(struct device *dev,
/* Make sure all pending I/O is finished */ /* Make sure all pending I/O is finished */
fsync_bdev(bdev); fsync_bdev(bdev);
zram_reset_device(zram);
set_capacity(zram->disk, 0);
mutex_unlock(&bdev->bd_mutex);
revalidate_disk(zram->disk);
bdput(bdev); bdput(bdev);
zram_reset_device(zram, true);
return len; return len;
out: out:
mutex_unlock(&bdev->bd_mutex);
bdput(bdev); bdput(bdev);
return ret; return ret;
} }
@ -1145,7 +1140,7 @@ static void __exit zram_exit(void)
* Shouldn't access zram->disk after destroy_device * Shouldn't access zram->disk after destroy_device
* because destroy_device already released zram->disk. * because destroy_device already released zram->disk.
*/ */
zram_reset_device(zram, false); zram_reset_device(zram);
} }
unregister_blkdev(zram_major, "zram"); unregister_blkdev(zram_major, "zram");