Commit d5c88b73 authored by Jan Schmidt's avatar Jan Schmidt
Browse files

Btrfs: bugfix: ignore the wrong key for indirect tree block backrefs 



The key we store with a tree block backref is only a hint. It is set when
the ref is created and can remain correct for a long time. As the tree is
rebalanced, however, eventually the key no longer points to the correct
destination.

With this patch, we change find_parent_nodes to no longer add keys unless it
knows for sure they're correct (e.g. because they're for an extent data
backref). Then when we later encounter a backref ref with no parent and no
key set, we grab the block and take the first key from the block itself.

Signed-off-by: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
parent dadcaf78

fs/btrfs/backref.c

+135 −50
Original line number Diff line number Diff line
@@ -30,16 +30,55 @@ 
struct __prelim_ref {

	struct list_head list;

	u64 root_id;

	struct btrfs_key key;

	struct btrfs_key key_for_search;

	int level;

	int count;

	u64 parent;

	u64 wanted_disk_byte;

};



/*

 * the rules for all callers of this function are:

 * - obtaining the parent is the goal

 * - if you add a key, you must know that it is a correct key

 * - if you cannot add the parent or a correct key, then we will look into the

 *   block later to set a correct key

 *

 * delayed refs

 * ============

 *        backref type | shared | indirect | shared | indirect

 * information         |   tree |     tree |   data |     data

 * --------------------+--------+----------+--------+----------

 *      parent logical |    y   |     -    |    -   |     -

 *      key to resolve |    -   |     y    |    y   |     y

 *  tree block logical |    -   |     -    |    -   |     -

 *  root for resolving |    y   |     y    |    y   |     y

 *

 * - column 1:       we've the parent -> done

 * - column 2, 3, 4: we use the key to find the parent

 *

 * on disk refs (inline or keyed)

 * ==============================

 *        backref type | shared | indirect | shared | indirect

 * information         |   tree |     tree |   data |     data

 * --------------------+--------+----------+--------+----------

 *      parent logical |    y   |     -    |    y   |     -

 *      key to resolve |    -   |     -    |    -   |     y

 *  tree block logical |    y   |     y    |    y   |     y

 *  root for resolving |    -   |     y    |    y   |     y

 *

 * - column 1, 3: we've the parent -> done

 * - column 2:    we take the first key from the block to find the parent

 *                (see __add_missing_keys)

 * - column 4:    we use the key to find the parent

 *

 * additional information that's available but not required to find the parent

 * block might help in merging entries to gain some speed.

 */



static int __add_prelim_ref(struct list_head *head, u64 root_id,

			    struct btrfs_key *key, int level, u64 parent,

			    u64 wanted_disk_byte, int count)

			    struct btrfs_key *key, int level,

			    u64 parent, u64 wanted_disk_byte, int count)

{

	struct __prelim_ref *ref;
@@ -50,9 +89,9 @@ static int __add_prelim_ref(struct list_head *head, u64 root_id, 


	ref->root_id = root_id;

	if (key)

		ref->key = *key;

		ref->key_for_search = *key;

	else

		memset(&ref->key, 0, sizeof(ref->key));

		memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));



	ref->level = level;

	ref->count = count;
@@ -152,12 +191,13 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info, 
		goto out;



	path->lowest_level = level;

	ret = btrfs_search_slot(NULL, root, &ref->key, path, 0, 0);

	ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path, 0, 0);

	pr_debug("search slot in root %llu (level %d, ref count %d) returned "

		 "%d for key (%llu %u %llu)\n",

		 (unsigned long long)ref->root_id, level, ref->count, ret,

		 (unsigned long long)ref->key.objectid, ref->key.type,

		 (unsigned long long)ref->key.offset);

		 (unsigned long long)ref->key_for_search.objectid,

		 ref->key_for_search.type,

		 (unsigned long long)ref->key_for_search.offset);

	if (ret < 0)

		goto out;
@@ -248,10 +288,65 @@ static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info, 
	return ret;

}



static inline int ref_for_same_block(struct __prelim_ref *ref1,

				     struct __prelim_ref *ref2)

{

	if (ref1->level != ref2->level)

		return 0;

	if (ref1->root_id != ref2->root_id)

		return 0;

	if (ref1->key_for_search.type != ref2->key_for_search.type)

		return 0;

	if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)

		return 0;

	if (ref1->key_for_search.offset != ref2->key_for_search.offset)

		return 0;

	if (ref1->parent != ref2->parent)

		return 0;



	return 1;

}



/*

 * read tree blocks and add keys where required.

 */

static int __add_missing_keys(struct btrfs_fs_info *fs_info,

			      struct list_head *head)

{

	struct list_head *pos;

	struct extent_buffer *eb;



	list_for_each(pos, head) {

		struct __prelim_ref *ref;

		ref = list_entry(pos, struct __prelim_ref, list);



		if (ref->parent)

			continue;

		if (ref->key_for_search.type)

			continue;

		BUG_ON(!ref->wanted_disk_byte);

		eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,

				     fs_info->tree_root->leafsize, 0);

		BUG_ON(!eb);

		btrfs_tree_read_lock(eb);

		if (btrfs_header_level(eb) == 0)

			btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);

		else

			btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);

		btrfs_tree_read_unlock(eb);

		free_extent_buffer(eb);

	}

	return 0;

}



/*

 * merge two lists of backrefs and adjust counts accordingly

 *

 * mode = 1: merge identical keys, if key is set

 *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.

 *           additionally, we could even add a key range for the blocks we

 *           looked into to merge even more (-> replace unresolved refs by those

 *           having a parent).

 * mode = 2: merge identical parents

 */

static int __merge_refs(struct list_head *head, int mode)
@@ -265,20 +360,21 @@ static int __merge_refs(struct list_head *head, int mode) 


		ref1 = list_entry(pos1, struct __prelim_ref, list);



		if (mode == 1 && ref1->key.type == 0)

			continue;

		for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;

		     pos2 = n2, n2 = pos2->next) {

			struct __prelim_ref *ref2;

			struct __prelim_ref *xchg;



			ref2 = list_entry(pos2, struct __prelim_ref, list);



			if (mode == 1) {

				if (memcmp(&ref1->key, &ref2->key,

					   sizeof(ref1->key)) ||

				    ref1->level != ref2->level ||

				    ref1->root_id != ref2->root_id)

				if (!ref_for_same_block(ref1, ref2))

					continue;

				if (!ref1->parent && ref2->parent) {

					xchg = ref1;

					ref1 = ref2;

					ref2 = xchg;

				}

				ref1->count += ref2->count;

			} else {

				if (ref1->parent != ref2->parent)
@@ -298,16 +394,17 @@ static int __merge_refs(struct list_head *head, int mode) 
 * smaller or equal that seq to the list

 */

static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,

			      struct btrfs_key *info_key,

			      struct list_head *prefs)

{

	struct btrfs_delayed_extent_op *extent_op = head->extent_op;

	struct rb_node *n = &head->node.rb_node;

	struct btrfs_key key;

	struct btrfs_key op_key = {0};

	int sgn;

	int ret = 0;



	if (extent_op && extent_op->update_key)

		btrfs_disk_key_to_cpu(info_key, &extent_op->key);

		btrfs_disk_key_to_cpu(&op_key, &extent_op->key);



	while ((n = rb_prev(n))) {

		struct btrfs_delayed_ref_node *node;
@@ -339,7 +436,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, 
			struct btrfs_delayed_tree_ref *ref;



			ref = btrfs_delayed_node_to_tree_ref(node);

			ret = __add_prelim_ref(prefs, ref->root, info_key,

			ret = __add_prelim_ref(prefs, ref->root, &op_key,

					       ref->level + 1, 0, node->bytenr,

					       node->ref_mod * sgn);

			break;
@@ -348,7 +445,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, 
			struct btrfs_delayed_tree_ref *ref;



			ref = btrfs_delayed_node_to_tree_ref(node);

			ret = __add_prelim_ref(prefs, ref->root, info_key,

			ret = __add_prelim_ref(prefs, ref->root, NULL,

					       ref->level + 1, ref->parent,

					       node->bytenr,

					       node->ref_mod * sgn);
@@ -356,8 +453,6 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, 
		}

		case BTRFS_EXTENT_DATA_REF_KEY: {

			struct btrfs_delayed_data_ref *ref;

			struct btrfs_key key;



			ref = btrfs_delayed_node_to_data_ref(node);



			key.objectid = ref->objectid;
@@ -370,7 +465,6 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, 
		}

		case BTRFS_SHARED_DATA_REF_KEY: {

			struct btrfs_delayed_data_ref *ref;

			struct btrfs_key key;



			ref = btrfs_delayed_node_to_data_ref(node);
@@ -396,8 +490,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, 
 */

static int __add_inline_refs(struct btrfs_fs_info *fs_info,

			     struct btrfs_path *path, u64 bytenr,

			     struct btrfs_key *info_key, int *info_level,

			     struct list_head *prefs)

			     int *info_level, struct list_head *prefs)

{

	int ret = 0;

	int slot;
@@ -426,12 +519,9 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info, 


	if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {

		struct btrfs_tree_block_info *info;

		struct btrfs_disk_key disk_key;



		info = (struct btrfs_tree_block_info *)ptr;

		*info_level = btrfs_tree_block_level(leaf, info);

		btrfs_tree_block_key(leaf, info, &disk_key);

		btrfs_disk_key_to_cpu(info_key, &disk_key);

		ptr += sizeof(struct btrfs_tree_block_info);

		BUG_ON(ptr > end);

	} else {
@@ -449,7 +539,7 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info, 


		switch (type) {

		case BTRFS_SHARED_BLOCK_REF_KEY:

			ret = __add_prelim_ref(prefs, 0, info_key,

			ret = __add_prelim_ref(prefs, 0, NULL,

						*info_level + 1, offset,

						bytenr, 1);

			break;
@@ -464,8 +554,9 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info, 
			break;

		}

		case BTRFS_TREE_BLOCK_REF_KEY:

			ret = __add_prelim_ref(prefs, offset, info_key,

					       *info_level + 1, 0, bytenr, 1);

			ret = __add_prelim_ref(prefs, offset, NULL,

					       *info_level + 1, 0,

					       bytenr, 1);

			break;

		case BTRFS_EXTENT_DATA_REF_KEY: {

			struct btrfs_extent_data_ref *dref;
@@ -479,8 +570,8 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info, 
			key.type = BTRFS_EXTENT_DATA_KEY;

			key.offset = btrfs_extent_data_ref_offset(leaf, dref);

			root = btrfs_extent_data_ref_root(leaf, dref);

			ret = __add_prelim_ref(prefs, root, &key, 0, 0, bytenr,

						count);

			ret = __add_prelim_ref(prefs, root, &key, 0, 0,

					       bytenr, count);

			break;

		}

		default:
@@ -498,8 +589,7 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info, 
 */

static int __add_keyed_refs(struct btrfs_fs_info *fs_info,

			    struct btrfs_path *path, u64 bytenr,

			    struct btrfs_key *info_key, int info_level,

			    struct list_head *prefs)

			    int info_level, struct list_head *prefs)

{

	struct btrfs_root *extent_root = fs_info->extent_root;

	int ret;
@@ -529,7 +619,7 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info, 


		switch (key.type) {

		case BTRFS_SHARED_BLOCK_REF_KEY:

			ret = __add_prelim_ref(prefs, 0, info_key,

			ret = __add_prelim_ref(prefs, 0, NULL,

						info_level + 1, key.offset,

						bytenr, 1);

			break;
@@ -545,8 +635,9 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info, 
			break;

		}

		case BTRFS_TREE_BLOCK_REF_KEY:

			ret = __add_prelim_ref(prefs, key.offset, info_key,

						info_level + 1, 0, bytenr, 1);

			ret = __add_prelim_ref(prefs, key.offset, NULL,

					       info_level + 1, 0,

					       bytenr, 1);

			break;

		case BTRFS_EXTENT_DATA_REF_KEY: {

			struct btrfs_extent_data_ref *dref;
@@ -588,7 +679,6 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans, 
{

	struct btrfs_key key;

	struct btrfs_path *path;

	struct btrfs_key info_key = { 0 };

	struct btrfs_delayed_ref_root *delayed_refs = NULL;

	struct btrfs_delayed_ref_head *head;

	int info_level = 0;
@@ -647,8 +737,7 @@ again: 
				btrfs_put_delayed_ref(&head->node);

				goto again;

			}

			ret = __add_delayed_refs(head, seq, &info_key,

						 &prefs_delayed);

			ret = __add_delayed_refs(head, seq, &prefs_delayed);

			if (ret) {

				spin_unlock(&delayed_refs->lock);

				goto out;
@@ -668,10 +757,10 @@ again: 
		if (key.objectid == bytenr &&

		    key.type == BTRFS_EXTENT_ITEM_KEY) {

			ret = __add_inline_refs(fs_info, path, bytenr,

						&info_key, &info_level, &prefs);

						&info_level, &prefs);

			if (ret)

				goto out;

			ret = __add_keyed_refs(fs_info, path, bytenr, &info_key,

			ret = __add_keyed_refs(fs_info, path, bytenr,

					       info_level, &prefs);

			if (ret)

				goto out;
@@ -679,16 +768,12 @@ again: 
	}

	btrfs_release_path(path);



	/*

	 * when adding the delayed refs above, the info_key might not have

	 * been known yet. Go over the list and replace the missing keys

	 */

	list_for_each_entry(ref, &prefs_delayed, list) {

		if ((ref->key.offset | ref->key.type | ref->key.objectid) == 0)

			memcpy(&ref->key, &info_key, sizeof(ref->key));

	}

	list_splice_init(&prefs_delayed, &prefs);



	ret = __add_missing_keys(fs_info, &prefs);

	if (ret)

		goto out;



	ret = __merge_refs(&prefs, 1);

	if (ret)

		goto out;

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