diff mbox

[12/18] Btrfs: Fix misuse of chunk mutex

Message ID 1409751347-5296-12-git-send-email-miaox@cn.fujitsu.com (mailing list archive)
State Accepted
Headers show

Commit Message

Miao Xie Sept. 3, 2014, 1:35 p.m. UTC 
There were several problems about chunk mutex usage:
- Lock chunk mutex when updating metadata. It would cause the nested
  deadlock because updating metadata might need allocate new chunks
  that need acquire chunk mutex. We remove chunk mutex at this case,
  because b-tree lock and other lock mechanism can help us.
- ABBA deadlock occured between device_list_mutex and chunk_mutex.
  When we update device status, we must acquire device_list_mutex at the
  beginning, and then we might get chunk_mutex during the device status
  update because we need allocate new chunks for metadata COW. But at
  most place, we acquire chunk_mutex at first and then acquire device list
  mutex. We need change the lock order.
- Some place we needn't acquire chunk_mutex. For example we needn't get
  chunk_mutex when we free a empty seed fs_devices structure.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/btrfs/dev-replace.c |   6 +--
 fs/btrfs/extent-tree.c |   2 -
 fs/btrfs/volumes.c     | 129 ++++++++++++++++++++++++-------------------------
 3 files changed, 65 insertions(+), 72 deletions(-)

Comments

Chris Mason Sept. 11, 2014, 3:39 p.m. UTC | #1 
On 09/03/2014 09:35 AM, Miao Xie wrote:
> There were several problems about chunk mutex usage:
> - Lock chunk mutex when updating metadata. It would cause the nested
>   deadlock because updating metadata might need allocate new chunks
>   that need acquire chunk mutex. We remove chunk mutex at this case,
>   because b-tree lock and other lock mechanism can help us.
> - ABBA deadlock occured between device_list_mutex and chunk_mutex.
>   When we update device status, we must acquire device_list_mutex at the
>   beginning, and then we might get chunk_mutex during the device status
>   update because we need allocate new chunks for metadata COW. But at
>   most place, we acquire chunk_mutex at first and then acquire device list
>   mutex. We need change the lock order.
> - Some place we needn't acquire chunk_mutex. For example we needn't get
>   chunk_mutex when we free a empty seed fs_devices structure.
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 9f22398d..357f911 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> 
> @@ -2619,10 +2615,23 @@ static int btrfs_relocate_chunk(struct btrfs_root *root,
>  	map = (struct map_lookup *)em->bdev;
>  
>  	for (i = 0; i < map->num_stripes; i++) {
> -		ret = btrfs_free_dev_extent(trans, map->stripes[i].dev,
> -					    map->stripes[i].physical);
> +		device = map->stripes[i].dev;
> +		ret = btrfs_free_dev_extent(trans, device,
> +					    map->stripes[i].physical,
> +					    &dev_extent_len);
>  		BUG_ON(ret);

gcc is worried that dev_extent_len may be used uninitialized here.  The
BUG_ON makes it unlikely we'll notice dev_extent_len, but I set it to
zero in my version here.

-chris
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diff mbox

Patch

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index da7ac14..aa4c828 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -510,8 +510,8 @@  static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 	WARN_ON(ret);
 
 	/* keep away write_all_supers() during the finishing procedure */
-	mutex_lock(&root->fs_info->chunk_mutex);
 	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
+	mutex_lock(&root->fs_info->chunk_mutex);
 	btrfs_dev_replace_lock(dev_replace);
 	dev_replace->replace_state =
 		scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
@@ -534,8 +534,8 @@  static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 			      src_device->devid,
 			      rcu_str_deref(tgt_device->name), scrub_ret);
 		btrfs_dev_replace_unlock(dev_replace);
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 		mutex_unlock(&root->fs_info->chunk_mutex);
+		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 		if (tgt_device)
 			btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
 		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
@@ -589,8 +589,8 @@  static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 	 * superblock is scratched out so that it is no longer marked to
 	 * belong to this filesystem.
 	 */
-	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 	mutex_unlock(&root->fs_info->chunk_mutex);
+	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 
 	/* write back the superblocks */
 	trans = btrfs_start_transaction(root, 0);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e105558..e1ad84e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9404,8 +9404,6 @@  int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 
 	memcpy(&key, &block_group->key, sizeof(key));
 
-	btrfs_clear_space_info_full(root->fs_info);
-
 	btrfs_put_block_group(block_group);
 	btrfs_put_block_group(block_group);
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9f22398d..357f911 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1264,7 +1264,7 @@  out:
 
 static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
 			  struct btrfs_device *device,
-			  u64 start)
+			  u64 start, u64 *dev_extent_len)
 {
 	int ret;
 	struct btrfs_path *path;
@@ -1306,13 +1306,8 @@  again:
 		goto out;
 	}
 
-	if (device->bytes_used > 0) {
-		u64 len = btrfs_dev_extent_length(leaf, extent);
-		btrfs_device_set_bytes_used(device, device->bytes_used - len);
-		spin_lock(&root->fs_info->free_chunk_lock);
-		root->fs_info->free_chunk_space += len;
-		spin_unlock(&root->fs_info->free_chunk_lock);
-	}
+	*dev_extent_len = btrfs_dev_extent_length(leaf, extent);
+
 	ret = btrfs_del_item(trans, root, path);
 	if (ret) {
 		btrfs_error(root->fs_info, ret,
@@ -1521,7 +1516,6 @@  static int btrfs_rm_dev_item(struct btrfs_root *root,
 	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
 	key.type = BTRFS_DEV_ITEM_KEY;
 	key.offset = device->devid;
-	lock_chunks(root);
 
 	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 	if (ret < 0)
@@ -1537,7 +1531,6 @@  static int btrfs_rm_dev_item(struct btrfs_root *root,
 		goto out;
 out:
 	btrfs_free_path(path);
-	unlock_chunks(root);
 	btrfs_commit_transaction(trans, root);
 	return ret;
 }
@@ -1726,9 +1719,7 @@  int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 			fs_devices = fs_devices->seed;
 		}
 		cur_devices->seed = NULL;
-		lock_chunks(root);
 		__btrfs_close_devices(cur_devices);
-		unlock_chunks(root);
 		free_fs_devices(cur_devices);
 	}
 
@@ -1990,11 +1981,12 @@  static int btrfs_prepare_sprout(struct btrfs_root *root)
 	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
 	list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices,
 			      synchronize_rcu);
+	list_for_each_entry(device, &seed_devices->devices, dev_list)
+		device->fs_devices = seed_devices;
 
+	lock_chunks(root);
 	list_splice_init(&fs_devices->alloc_list, &seed_devices->alloc_list);
-	list_for_each_entry(device, &seed_devices->devices, dev_list) {
-		device->fs_devices = seed_devices;
-	}
+	unlock_chunks(root);
 
 	fs_devices->seeding = 0;
 	fs_devices->num_devices = 0;
@@ -2155,8 +2147,6 @@  int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 		goto error;
 	}
 
-	lock_chunks(root);
-
 	q = bdev_get_queue(bdev);
 	if (blk_queue_discard(q))
 		device->can_discard = 1;
@@ -2185,6 +2175,7 @@  int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 	device->fs_devices = root->fs_info->fs_devices;
 
 	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
+	lock_chunks(root);
 	list_add_rcu(&device->dev_list, &root->fs_info->fs_devices->devices);
 	list_add(&device->dev_alloc_list,
 		 &root->fs_info->fs_devices->alloc_list);
@@ -2212,15 +2203,34 @@  int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 	/* add sysfs device entry */
 	btrfs_kobj_add_device(root->fs_info, device);
 
+	/*
+	 * we've got more storage, clear any full flags on the space
+	 * infos
+	 */
+	btrfs_clear_space_info_full(root->fs_info);
+
+	unlock_chunks(root);
 	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 
 	if (seeding_dev) {
-		char fsid_buf[BTRFS_UUID_UNPARSED_SIZE];
+		lock_chunks(root);
 		ret = init_first_rw_device(trans, root, device);
+		unlock_chunks(root);
 		if (ret) {
 			btrfs_abort_transaction(trans, root, ret);
 			goto error_trans;
 		}
+	}
+
+	ret = btrfs_add_device(trans, root, device);
+	if (ret) {
+		btrfs_abort_transaction(trans, root, ret);
+		goto error_trans;
+	}
+
+	if (seeding_dev) {
+		char fsid_buf[BTRFS_UUID_UNPARSED_SIZE];
+
 		ret = btrfs_finish_sprout(trans, root);
 		if (ret) {
 			btrfs_abort_transaction(trans, root, ret);
@@ -2234,21 +2244,8 @@  int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 						root->fs_info->fsid);
 		if (kobject_rename(&root->fs_info->super_kobj, fsid_buf))
 			goto error_trans;
-	} else {
-		ret = btrfs_add_device(trans, root, device);
-		if (ret) {
-			btrfs_abort_transaction(trans, root, ret);
-			goto error_trans;
-		}
 	}
 
-	/*
-	 * we've got more storage, clear any full flags on the space
-	 * infos
-	 */
-	btrfs_clear_space_info_full(root->fs_info);
-
-	unlock_chunks(root);
 	root->fs_info->num_tolerated_disk_barrier_failures =
 		btrfs_calc_num_tolerated_disk_barrier_failures(root->fs_info);
 	ret = btrfs_commit_transaction(trans, root);
@@ -2280,7 +2277,6 @@  int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 	return ret;
 
 error_trans:
-	unlock_chunks(root);
 	btrfs_end_transaction(trans, root);
 	rcu_string_free(device->name);
 	btrfs_kobj_rm_device(root->fs_info, device);
@@ -2449,20 +2445,27 @@  out:
 	return ret;
 }
 
-static int __btrfs_grow_device(struct btrfs_trans_handle *trans,
+int btrfs_grow_device(struct btrfs_trans_handle *trans,
 		      struct btrfs_device *device, u64 new_size)
 {
 	struct btrfs_super_block *super_copy =
 		device->dev_root->fs_info->super_copy;
 	struct btrfs_fs_devices *fs_devices;
-	u64 old_total = btrfs_super_total_bytes(super_copy);
-	u64 diff = new_size - device->total_bytes;
+	u64 old_total;
+	u64 diff;
 
 	if (!device->writeable)
 		return -EACCES;
+
+	lock_chunks(device->dev_root);
+	old_total = btrfs_super_total_bytes(super_copy);
+	diff = new_size - device->total_bytes;
+
 	if (new_size <= device->total_bytes ||
-	    device->is_tgtdev_for_dev_replace)
+	    device->is_tgtdev_for_dev_replace) {
+		unlock_chunks(device->dev_root);
 		return -EINVAL;
+	}
 
 	fs_devices = device->dev_root->fs_info->fs_devices;
 
@@ -2475,20 +2478,11 @@  static int __btrfs_grow_device(struct btrfs_trans_handle *trans,
 	if (list_empty(&device->resized_list))
 		list_add_tail(&device->resized_list,
 			      &fs_devices->resized_devices);
+	unlock_chunks(device->dev_root);
 
 	return btrfs_update_device(trans, device);
 }
 
-int btrfs_grow_device(struct btrfs_trans_handle *trans,
-		      struct btrfs_device *device, u64 new_size)
-{
-	int ret;
-	lock_chunks(device->dev_root);
-	ret = __btrfs_grow_device(trans, device, new_size);
-	unlock_chunks(device->dev_root);
-	return ret;
-}
-
 static int btrfs_free_chunk(struct btrfs_trans_handle *trans,
 			    struct btrfs_root *root,
 			    u64 chunk_tree, u64 chunk_objectid,
@@ -2540,6 +2534,7 @@  static int btrfs_del_sys_chunk(struct btrfs_root *root, u64 chunk_objectid, u64
 	u32 cur;
 	struct btrfs_key key;
 
+	lock_chunks(root);
 	array_size = btrfs_super_sys_array_size(super_copy);
 
 	ptr = super_copy->sys_chunk_array;
@@ -2569,6 +2564,7 @@  static int btrfs_del_sys_chunk(struct btrfs_root *root, u64 chunk_objectid, u64
 			cur += len;
 		}
 	}
+	unlock_chunks(root);
 	return ret;
 }
 
@@ -2579,8 +2575,10 @@  static int btrfs_relocate_chunk(struct btrfs_root *root,
 	struct extent_map_tree *em_tree;
 	struct btrfs_root *extent_root;
 	struct btrfs_trans_handle *trans;
+	struct btrfs_device *device;
 	struct extent_map *em;
 	struct map_lookup *map;
+	u64 dev_extent_len;
 	int ret;
 	int i;
 
@@ -2604,8 +2602,6 @@  static int btrfs_relocate_chunk(struct btrfs_root *root,
 		return ret;
 	}
 
-	lock_chunks(root);
-
 	/*
 	 * step two, delete the device extents and the
 	 * chunk tree entries
@@ -2619,10 +2615,23 @@  static int btrfs_relocate_chunk(struct btrfs_root *root,
 	map = (struct map_lookup *)em->bdev;
 
 	for (i = 0; i < map->num_stripes; i++) {
-		ret = btrfs_free_dev_extent(trans, map->stripes[i].dev,
-					    map->stripes[i].physical);
+		device = map->stripes[i].dev;
+		ret = btrfs_free_dev_extent(trans, device,
+					    map->stripes[i].physical,
+					    &dev_extent_len);
 		BUG_ON(ret);
 
+		if (device->bytes_used > 0) {
+			lock_chunks(root);
+			btrfs_device_set_bytes_used(device,
+					device->bytes_used - dev_extent_len);
+			spin_lock(&root->fs_info->free_chunk_lock);
+			root->fs_info->free_chunk_space += dev_extent_len;
+			spin_unlock(&root->fs_info->free_chunk_lock);
+			btrfs_clear_space_info_full(root->fs_info);
+			unlock_chunks(root);
+		}
+
 		if (map->stripes[i].dev) {
 			ret = btrfs_update_device(trans, map->stripes[i].dev);
 			BUG_ON(ret);
@@ -2652,7 +2661,6 @@  static int btrfs_relocate_chunk(struct btrfs_root *root,
 	/* once for us */
 	free_extent_map(em);
 
-	unlock_chunks(root);
 	btrfs_end_transaction(trans, root);
 	return 0;
 }
@@ -4029,16 +4037,12 @@  again:
 		list_add_tail(&device->resized_list,
 			      &root->fs_info->fs_devices->resized_devices);
 
-	/* Now btrfs_update_device() will change the on-disk size. */
-	ret = btrfs_update_device(trans, device);
-	if (ret) {
-		unlock_chunks(root);
-		btrfs_end_transaction(trans, root);
-		goto done;
-	}
 	WARN_ON(diff > old_total);
 	btrfs_set_super_total_bytes(super_copy, old_total - diff);
 	unlock_chunks(root);
+
+	/* Now btrfs_update_device() will change the on-disk size. */
+	ret = btrfs_update_device(trans, device);
 	btrfs_end_transaction(trans, root);
 done:
 	btrfs_free_path(path);
@@ -4612,15 +4616,6 @@  static noinline int init_first_rw_device(struct btrfs_trans_handle *trans,
 	alloc_profile = btrfs_get_alloc_profile(fs_info->chunk_root, 0);
 	ret = __btrfs_alloc_chunk(trans, extent_root, sys_chunk_offset,
 				  alloc_profile);
-	if (ret) {
-		btrfs_abort_transaction(trans, root, ret);
-		goto out;
-	}
-
-	ret = btrfs_add_device(trans, fs_info->chunk_root, device);
-	if (ret)
-		btrfs_abort_transaction(trans, root, ret);
-out:
 	return ret;
 }