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author | Sergey Senozhatsky <sergey.senozhatsky@gmail.com> | 2015-02-12 23:00:39 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-13 02:54:11 (GMT) |
commit | a096cafc31862c54da0b56c8441dc14023437008 (patch) | |
tree | e79e5326429f2c91b180091e114b11ec8f2eaf39 | |
parent | ba6b17d68c8e3aa8d55d0474299cb931965c5ea5 (diff) | |
download | linux-a096cafc31862c54da0b56c8441dc14023437008.tar.xz |
zram: rework reset and destroy path
We need to return set_capacity(disk, 0) from reset_store() back to
zram_reset_device(), a catch by Ganesh Mahendran. Potentially, we can
race set_capacity() calls from init and reset paths.
The problem is that zram_reset_device() is also getting called from
zram_exit(), which performs operations in misleading reversed order -- we
first create_device() and then init it, while zram_exit() perform
destroy_device() first and then does zram_reset_device(). This is done to
remove sysfs group before we reset device, so we can continue with device
reset/destruction not being raced by sysfs attr write (f.e. disksize).
Apart from that, destroy_device() releases zram->disk (but we still have
->disk pointer), so we cannot acces zram->disk in later
zram_reset_device() call, which may cause additional errors in the future.
So, this patch rework and cleanup destroy path.
1) remove several unneeded goto labels in zram_init()
2) factor out zram_init() error path and zram_exit() into
destroy_devices() function, which takes the number of devices to
destroy as its argument.
3) remove sysfs group in destroy_devices() first, so we can reorder
operations -- reset device (as expected) goes before disk destroy and
queue cleanup. So we can always access ->disk in zram_reset_device().
4) and, finally, return set_capacity() back under ->init_lock.
[akpm@linux-foundation.org: tweak comment]
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | drivers/block/zram/zram_drv.c | 75 |
1 files changed, 33 insertions, 42 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 2607bd9..81ac8fd 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -732,8 +732,9 @@ static void zram_reset_device(struct zram *zram) zram->meta = NULL; /* Reset stats */ memset(&zram->stats, 0, sizeof(zram->stats)); - zram->disksize = 0; + set_capacity(zram->disk, 0); + up_write(&zram->init_lock); } @@ -826,7 +827,6 @@ static ssize_t reset_store(struct device *dev, /* Make sure all pending I/O is finished */ fsync_bdev(bdev); zram_reset_device(zram); - set_capacity(zram->disk, 0); mutex_unlock(&bdev->bd_mutex); revalidate_disk(zram->disk); @@ -1112,15 +1112,31 @@ out: return ret; } -static void destroy_device(struct zram *zram) +static void destroy_devices(unsigned int nr) { - sysfs_remove_group(&disk_to_dev(zram->disk)->kobj, - &zram_disk_attr_group); + struct zram *zram; + unsigned int i; - del_gendisk(zram->disk); - put_disk(zram->disk); + for (i = 0; i < nr; i++) { + zram = &zram_devices[i]; + /* + * Remove sysfs first, so no one will perform a disksize + * store while we destroy the devices + */ + sysfs_remove_group(&disk_to_dev(zram->disk)->kobj, + &zram_disk_attr_group); - blk_cleanup_queue(zram->queue); + zram_reset_device(zram); + + del_gendisk(zram->disk); + put_disk(zram->disk); + + blk_cleanup_queue(zram->queue); + } + + kfree(zram_devices); + unregister_blkdev(zram_major, "zram"); + pr_info("Destroyed %u device(s)\n", nr); } static int __init zram_init(void) @@ -1130,64 +1146,39 @@ static int __init zram_init(void) if (num_devices > max_num_devices) { pr_warn("Invalid value for num_devices: %u\n", num_devices); - ret = -EINVAL; - goto out; + return -EINVAL; } zram_major = register_blkdev(0, "zram"); if (zram_major <= 0) { pr_warn("Unable to get major number\n"); - ret = -EBUSY; - goto out; + return -EBUSY; } /* Allocate the device array and initialize each one */ zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL); if (!zram_devices) { - ret = -ENOMEM; - goto unregister; + unregister_blkdev(zram_major, "zram"); + return -ENOMEM; } for (dev_id = 0; dev_id < num_devices; dev_id++) { ret = create_device(&zram_devices[dev_id], dev_id); if (ret) - goto free_devices; + goto out_error; } - pr_info("Created %u device(s) ...\n", num_devices); - + pr_info("Created %u device(s)\n", num_devices); return 0; -free_devices: - while (dev_id) - destroy_device(&zram_devices[--dev_id]); - kfree(zram_devices); -unregister: - unregister_blkdev(zram_major, "zram"); -out: +out_error: + destroy_devices(dev_id); return ret; } static void __exit zram_exit(void) { - int i; - struct zram *zram; - - for (i = 0; i < num_devices; i++) { - zram = &zram_devices[i]; - - destroy_device(zram); - /* - * Shouldn't access zram->disk after destroy_device - * because destroy_device already released zram->disk. - */ - zram_reset_device(zram); - } - - unregister_blkdev(zram_major, "zram"); - - kfree(zram_devices); - pr_debug("Cleanup done!\n"); + destroy_devices(num_devices); } module_init(zram_init); |