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Commit cea67ab9 authored by Jeff Mahoney's avatar Jeff Mahoney Committed by David Sterba
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btrfs: clean the old superblocks before freeing the device 



btrfs_rm_device frees the block device but then re-opens it using
the saved device name.  A race exists between the close and the
re-open that allows the block size to be changed.  The result
is getting stuck forever in the reclaim loop in __getblk_slow.

This patch moves the superblock cleanup before closing the block
device, which is also consistent with other callers.  We also don't
need a private copy of dev_name as the whole routine operates under
the uuid_mutex.

Signed-off-by: default avatarJeff Mahoney <jeffm@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 02794222

fs/btrfs/volumes.c

+11 −27
Original line number Diff line number Diff line
@@ -1846,7 +1846,6 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path, u64 devid) 
	u64 num_devices;

	int ret = 0;

	bool clear_super = false;

	char *dev_name = NULL;



	mutex_lock(&uuid_mutex);
@@ -1882,11 +1881,6 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path, u64 devid) 
		list_del_init(&device->dev_alloc_list);

		device->fs_devices->rw_devices--;

		unlock_chunks(root);

		dev_name = kstrdup(device->name->str, GFP_KERNEL);

		if (!dev_name) {

			ret = -ENOMEM;

			goto error_undo;

		}

		clear_super = true;

	}
@@ -1936,14 +1930,21 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path, u64 devid) 
		btrfs_sysfs_rm_device_link(root->fs_info->fs_devices, device);

	}



	btrfs_close_bdev(device);



	call_rcu(&device->rcu, free_device);



	num_devices = btrfs_super_num_devices(root->fs_info->super_copy) - 1;

	btrfs_set_super_num_devices(root->fs_info->super_copy, num_devices);

	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);



	/*

	 * at this point, the device is zero sized and detached from

	 * the devices list.  All that's left is to zero out the old

	 * supers and free the device.

	 */

	if (device->writeable)

		btrfs_scratch_superblocks(device->bdev, device->name->str);



	btrfs_close_bdev(device);

	call_rcu(&device->rcu, free_device);



	if (cur_devices->open_devices == 0) {

		struct btrfs_fs_devices *fs_devices;

		fs_devices = root->fs_info->fs_devices;
@@ -1962,24 +1963,7 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path, u64 devid) 
	root->fs_info->num_tolerated_disk_barrier_failures =

		btrfs_calc_num_tolerated_disk_barrier_failures(root->fs_info);



	/*

	 * at this point, the device is zero sized.  We want to

	 * remove it from the devices list and zero out the old super

	 */

	if (clear_super) {

		struct block_device *bdev;



		bdev = blkdev_get_by_path(dev_name, FMODE_READ | FMODE_EXCL,

						root->fs_info->bdev_holder);

		if (!IS_ERR(bdev)) {

			btrfs_scratch_superblocks(bdev, dev_name);

			blkdev_put(bdev, FMODE_READ | FMODE_EXCL);

		}

	}



out:

	kfree(dev_name);



	mutex_unlock(&uuid_mutex);

	return ret;