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authorSergey Senozhatsky <sergey.senozhatsky@gmail.com>2015-02-13 00:00:39 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-13 03:54:11 +0100
commita096cafc31862c54da0b56c8441dc14023437008 (patch)
treee79e5326429f2c91b180091e114b11ec8f2eaf39 /drivers/block/zram
parentzram: fix umount-reset_store-mount race condition (diff)
downloadlinux-a096cafc31862c54da0b56c8441dc14023437008.tar.xz
linux-a096cafc31862c54da0b56c8441dc14023437008.zip
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>
Diffstat (limited to 'drivers/block/zram')
-rw-r--r--drivers/block/zram/zram_drv.c75
1 files changed, 33 insertions, 42 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 2607bd9f4955..81ac8fd53340 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);