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Commit c974c464 authored by Wang Shilong's avatar Wang Shilong Committed by Chris Mason
Browse files

Btrfs: fix an oops when doing balance relocation 



I hit an oops when inserting reloc root into @reloc_root_tree(it can be
easily triggered when forcing cow for relocation root)

[  866.494539]  [<ffffffffa0499579>] btrfs_init_reloc_root+0x79/0xb0 [btrfs]
[  866.495321]  [<ffffffffa044c240>] record_root_in_trans+0xb0/0x110 [btrfs]
[  866.496109]  [<ffffffffa044d758>] btrfs_record_root_in_trans+0x48/0x80 [btrfs]
[  866.496908]  [<ffffffffa0494da8>] select_reloc_root+0xa8/0x210 [btrfs]
[  866.497703]  [<ffffffffa0495c8a>] do_relocation+0x16a/0x540 [btrfs]

This is because reloc root inserted into @reloc_root_tree is not within one
transaction,reloc root may be cowed and root block bytenr will be reused then
oops happens.We should update reloc root in @reloc_root_tree when cow reloc
root node, fix it.

Signed-off-by: default avatarWang Shilong <wangsl.fnst@cn.fujitsu.com>
Reviewed-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 639eefc8

fs/btrfs/relocation.c

+47 −23
Original line number Diff line number Diff line
@@ -1264,10 +1264,10 @@ static int __must_check __add_reloc_root(struct btrfs_root *root) 
}



/*

 * helper to update/delete the 'address of tree root -> reloc tree'

 * helper to delete the 'address of tree root -> reloc tree'

 * mapping

 */

static int __update_reloc_root(struct btrfs_root *root, int del)

static void __del_reloc_root(struct btrfs_root *root)

{

	struct rb_node *rb_node;

	struct mapping_node *node = NULL;
@@ -1275,7 +1275,36 @@ static int __update_reloc_root(struct btrfs_root *root, int del) 


	spin_lock(&rc->reloc_root_tree.lock);

	rb_node = tree_search(&rc->reloc_root_tree.rb_root,

			      root->commit_root->start);

			      root->node->start);

	if (rb_node) {

		node = rb_entry(rb_node, struct mapping_node, rb_node);

		rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);

	}

	spin_unlock(&rc->reloc_root_tree.lock);



	if (!node)

		return;

	BUG_ON((struct btrfs_root *)node->data != root);



	spin_lock(&root->fs_info->trans_lock);

	list_del_init(&root->root_list);

	spin_unlock(&root->fs_info->trans_lock);

	kfree(node);

}



/*

 * helper to update the 'address of tree root -> reloc tree'

 * mapping

 */

static int __update_reloc_root(struct btrfs_root *root, u64 new_bytenr)

{

	struct rb_node *rb_node;

	struct mapping_node *node = NULL;

	struct reloc_control *rc = root->fs_info->reloc_ctl;



	spin_lock(&rc->reloc_root_tree.lock);

	rb_node = tree_search(&rc->reloc_root_tree.rb_root,

			      root->node->start);

	if (rb_node) {

		node = rb_entry(rb_node, struct mapping_node, rb_node);

		rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
@@ -1286,20 +1315,13 @@ static int __update_reloc_root(struct btrfs_root *root, int del) 
		return 0;

	BUG_ON((struct btrfs_root *)node->data != root);



	if (!del) {

	spin_lock(&rc->reloc_root_tree.lock);

		node->bytenr = root->node->start;

	node->bytenr = new_bytenr;

	rb_node = tree_insert(&rc->reloc_root_tree.rb_root,

			      node->bytenr, &node->rb_node);

	spin_unlock(&rc->reloc_root_tree.lock);

	if (rb_node)

		backref_tree_panic(rb_node, -EEXIST, node->bytenr);

	} else {

		spin_lock(&root->fs_info->trans_lock);

		list_del_init(&root->root_list);

		spin_unlock(&root->fs_info->trans_lock);

		kfree(node);

	}

	return 0;

}
@@ -1420,7 +1442,6 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans, 
{

	struct btrfs_root *reloc_root;

	struct btrfs_root_item *root_item;

	int del = 0;

	int ret;



	if (!root->reloc_root)
@@ -1432,11 +1453,9 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans, 
	if (root->fs_info->reloc_ctl->merge_reloc_tree &&

	    btrfs_root_refs(root_item) == 0) {

		root->reloc_root = NULL;

		del = 1;

		__del_reloc_root(reloc_root);

	}



	__update_reloc_root(reloc_root, del);



	if (reloc_root->commit_root != reloc_root->node) {

		btrfs_set_root_node(root_item, reloc_root->node);

		free_extent_buffer(reloc_root->commit_root);
@@ -2287,7 +2306,7 @@ void free_reloc_roots(struct list_head *list) 
	while (!list_empty(list)) {

		reloc_root = list_entry(list->next, struct btrfs_root,

					root_list);

		__update_reloc_root(reloc_root, 1);

		__del_reloc_root(reloc_root);

		free_extent_buffer(reloc_root->node);

		free_extent_buffer(reloc_root->commit_root);

		kfree(reloc_root);
@@ -2332,7 +2351,7 @@ again: 


			ret = merge_reloc_root(rc, root);

			if (ret) {

				__update_reloc_root(reloc_root, 1);

				__del_reloc_root(reloc_root);

				free_extent_buffer(reloc_root->node);

				free_extent_buffer(reloc_root->commit_root);

				kfree(reloc_root);
@@ -4522,6 +4541,11 @@ int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans, 
	BUG_ON(rc->stage == UPDATE_DATA_PTRS &&

	       root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);



	if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {

		if (buf == root->node)

			__update_reloc_root(root, cow->start);

	}



	level = btrfs_header_level(buf);

	if (btrfs_header_generation(buf) <=

	    btrfs_root_last_snapshot(&root->root_item))