Patch "btrfs: clean the old superblocks before freeing the device" has been added to the 4.8-stable tree

PATCH [email protected] 1 participant 1 message Jan 4, 2017

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2017-01-04 09:46 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

btrfs: clean the old superblocks before freeing the device

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
btrfs-clean-the-old-superblocks-before-freeing-the-device.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From cea67ab92d3d4da9f2b4141d87cb8664757daca0 Mon Sep 17 00:00:00 2001

From: Jeff Mahoney <[email protected]>
Date: Tue, 20 Sep 2016 08:50:21 -0400
Subject: btrfs: clean the old superblocks before freeing the device

From: Jeff Mahoney <[email protected]>

commit cea67ab92d3d4da9f2b4141d87cb8664757daca0 upstream.

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 Jeff Mahoney <[email protected]>

Reviewed-by David Sterba <[email protected]>

Signed-off-by David Sterba <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 fs/btrfs/volumes.c |   38 +++++++++++---------------------------
 1 file changed, 11 insertions(+), 27 deletions(-)

fs/btrfs/volumes.c +11 ~~-27~~

@@ -1846,7 +1846,6 @@ int btrfs_rm_device(struct btrfs_root *r
 	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 *r
 		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 *r
 		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 *r
 	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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/btrfs-clean-the-old-superblocks-before-freeing-the-device.patch queue-4.8/btrfs-fix-bug_on-in-btrfs_mark_buffer_dirty.patch