commit fef912bf860e upstream. commit 98af4d4df889 upstream.
I got a report from Howard Chen that he saw zram and sysfs race(ie, zram block device file is created but sysfs for it isn't yet) when he tried to create new zram devices via hotadd knob.
v4.20 kernel fixes it by [1, 2] but it's too large size to merge into -stable so this patch fixes the problem by registering defualt group by Greg KH's approach[3].
This patch should be applied to every stable tree [3.16+] currently existing from kernel.org because the problem was introduced at 2.6.37 by [4].
[1] fef912bf860e, block: genhd: add 'groups' argument to device_add_disk [2] 98af4d4df889, zram: register default groups with device_add_disk() [3] http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/ [4] 33863c21e69e9, Staging: zram: Replace ioctls with sysfs interface
Cc: Sergey Senozhatsky sergey.senozhatsky@gmail.com Cc: Hannes Reinecke hare@suse.com Tested-by: Howard Chen howardsoc@google.com Signed-off-by: Minchan Kim minchan@kernel.org --- drivers/block/zram/zram_drv.c | 26 ++++++-------------------- 1 file changed, 6 insertions(+), 20 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index a1d6b5597c17..66921427d109 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1636,6 +1636,11 @@ static const struct attribute_group zram_disk_attr_group = { .attrs = zram_disk_attrs, };
+static const struct attribute_group *zram_disk_attr_groups[] = { + &zram_disk_attr_group, + NULL, +}; + /* * Allocate and initialize new zram device. the function returns * '>= 0' device_id upon success, and negative value otherwise. @@ -1716,24 +1721,15 @@ static int zram_add(void)
zram->disk->queue->backing_dev_info->capabilities |= (BDI_CAP_STABLE_WRITES | BDI_CAP_SYNCHRONOUS_IO); + disk_to_dev(zram->disk)->groups = zram_disk_attr_groups; add_disk(zram->disk);
- ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj, - &zram_disk_attr_group); - if (ret < 0) { - pr_err("Error creating sysfs group for device %d\n", - device_id); - goto out_free_disk; - } strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
zram_debugfs_register(zram); pr_info("Added device: %s\n", zram->disk->disk_name); return device_id;
-out_free_disk: - del_gendisk(zram->disk); - put_disk(zram->disk); out_free_queue: blk_cleanup_queue(queue); out_free_idr: @@ -1762,16 +1758,6 @@ static int zram_remove(struct zram *zram) mutex_unlock(&bdev->bd_mutex);
zram_debugfs_unregister(zram); - /* - * Remove sysfs first, so no one will perform a disksize - * store while we destroy the devices. This also helps during - * hot_remove -- zram_reset_device() is the last holder of - * ->init_lock, no later/concurrent disksize_store() or any - * other sysfs handlers are possible. - */ - sysfs_remove_group(&disk_to_dev(zram->disk)->kobj, - &zram_disk_attr_group); - /* Make sure all the pending I/O are finished */ fsync_bdev(bdev); zram_reset_device(zram);