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Commit 5bc7247a authored by Miao Xie's avatar Miao Xie Committed by Josef Bacik
Browse files

Btrfs: fix broken nocow after balance 



Balance will create reloc_root for each fs root, and it's going to
record last_snapshot to filter shared blocks.  The side effect of
setting last_snapshot is to break nocow attributes of files.

Since the extents are not shared by the relocation tree after the balance,
we can recover the old last_snapshot safely if no one snapshoted the
source tree. We fix the above problem by this way.

Reported-by: default avatarKyle Gates <kylegates@hotmail.com>
Signed-off-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
parent 8c2a1a30

fs/btrfs/relocation.c

+44 −0
Original line number Diff line number Diff line
@@ -1305,6 +1305,7 @@ static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans, 
	struct extent_buffer *eb;

	struct btrfs_root_item *root_item;

	struct btrfs_key root_key;

	u64 last_snap = 0;

	int ret;



	root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
@@ -1320,6 +1321,7 @@ static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans, 
				      BTRFS_TREE_RELOC_OBJECTID);

		BUG_ON(ret);



		last_snap = btrfs_root_last_snapshot(&root->root_item);

		btrfs_set_root_last_snapshot(&root->root_item,

					     trans->transid - 1);

	} else {
@@ -1345,6 +1347,12 @@ static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans, 
		memset(&root_item->drop_progress, 0,

		       sizeof(struct btrfs_disk_key));

		root_item->drop_level = 0;

		/*

		 * abuse rtransid, it is safe because it is impossible to

		 * receive data into a relocation tree.

		 */

		btrfs_set_root_rtransid(root_item, last_snap);

		btrfs_set_root_otransid(root_item, trans->transid);

	}



	btrfs_tree_unlock(eb);
@@ -2272,8 +2280,12 @@ void free_reloc_roots(struct list_head *list) 
static noinline_for_stack

int merge_reloc_roots(struct reloc_control *rc)

{

	struct btrfs_trans_handle *trans;

	struct btrfs_root *root;

	struct btrfs_root *reloc_root;

	u64 last_snap;

	u64 otransid;

	u64 objectid;

	LIST_HEAD(reloc_roots);

	int found = 0;

	int ret = 0;
@@ -2307,12 +2319,44 @@ int merge_reloc_roots(struct reloc_control *rc) 
		} else {

			list_del_init(&reloc_root->root_list);

		}



		/*

		 * we keep the old last snapshod transid in rtranid when we

		 * created the relocation tree.

		 */

		last_snap = btrfs_root_rtransid(&reloc_root->root_item);

		otransid = btrfs_root_otransid(&reloc_root->root_item);

		objectid = reloc_root->root_key.offset;



		ret = btrfs_drop_snapshot(reloc_root, rc->block_rsv, 0, 1);

		if (ret < 0) {

			if (list_empty(&reloc_root->root_list))

				list_add_tail(&reloc_root->root_list,

					      &reloc_roots);

			goto out;

		} else if (!ret) {

			/*

			 * recover the last snapshot tranid to avoid

			 * the space balance break NOCOW.

			 */

			root = read_fs_root(rc->extent_root->fs_info,

					    objectid);

			if (IS_ERR(root))

				continue;



			if (btrfs_root_refs(&root->root_item) == 0)

				continue;



			trans = btrfs_join_transaction(root);

			BUG_ON(IS_ERR(trans));



			/* Check if the fs/file tree was snapshoted or not. */

			if (btrfs_root_last_snapshot(&root->root_item) ==

			    otransid - 1)

				btrfs_set_root_last_snapshot(&root->root_item,

							     last_snap);

				

			btrfs_end_transaction(trans, root);

		}

	}