1 files changed, 103 insertions, 35 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index dce3a16996b9..18374a6d05bd 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -138,6 +138,7 @@ struct share_check {
 	u64 root_objectid;
 	u64 inum;
 	int share_count;
+	bool have_delayed_delete_refs;
 };
 
 static inline int extent_is_shared(struct share_check *sc)
@@ -288,8 +289,10 @@ static void prelim_release(struct preftree *preftree)
 	struct prelim_ref *ref, *next_ref;
 
 	rbtree_postorder_for_each_entry_safe(ref, next_ref,
-					     &preftree->root.rb_root, rbnode)
+					     &preftree->root.rb_root, rbnode) {
+		free_inode_elem_list(ref->inode_list);
 		free_pref(ref);
+	}
 
 	preftree->root = RB_ROOT_CACHED;
 	preftree->count = 0;
@@ -647,6 +650,18 @@ unode_aux_to_inode_list(struct ulist_node *node)
 	return (struct extent_inode_elem *)(uintptr_t)node->aux;
 }
 
+static void free_leaf_list(struct ulist *ulist)
+{
+	struct ulist_node *node;
+	struct ulist_iterator uiter;
+
+	ULIST_ITER_INIT(&uiter);
+	while ((node = ulist_next(ulist, &uiter)))
+		free_inode_elem_list(unode_aux_to_inode_list(node));
+
+	ulist_free(ulist);
+}
+
 /*
  * We maintain three separate rbtrees: one for direct refs, one for
  * indirect refs which have a key, and one for indirect refs which do not
@@ -761,7 +776,11 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
 		cond_resched();
 	}
 out:
-	ulist_free(parents);
+	/*
+	 * We may have inode lists attached to refs in the parents ulist, so we
+	 * must free them before freeing the ulist and its refs.
+	 */
+	free_leaf_list(parents);
 	return ret;
 }
 
@@ -820,16 +839,11 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
 			    struct preftrees *preftrees, struct share_check *sc)
 {
 	struct btrfs_delayed_ref_node *node;
-	struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 	struct btrfs_key key;
-	struct btrfs_key tmp_op_key;
 	struct rb_node *n;
 	int count;
 	int ret = 0;
 
-	if (extent_op && extent_op->update_key)
-		btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
-
 	spin_lock(&head->lock);
 	for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
 		node = rb_entry(n, struct btrfs_delayed_ref_node,
@@ -855,10 +869,16 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
 		case BTRFS_TREE_BLOCK_REF_KEY: {
 			/* NORMAL INDIRECT METADATA backref */
 			struct btrfs_delayed_tree_ref *ref;
+			struct btrfs_key *key_ptr = NULL;
+
+			if (head->extent_op && head->extent_op->update_key) {
+				btrfs_disk_key_to_cpu(&key, &head->extent_op->key);
+				key_ptr = &key;
+			}
 
 			ref = btrfs_delayed_node_to_tree_ref(node);
 			ret = add_indirect_ref(fs_info, preftrees, ref->root,
-					       &tmp_op_key, ref->level + 1,
+					       key_ptr, ref->level + 1,
 					       node->bytenr, count, sc,
 					       GFP_ATOMIC);
 			break;
@@ -884,13 +904,22 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
 			key.offset = ref->offset;
 
 			/*
-			 * Found a inum that doesn't match our known inum, we
-			 * know it's shared.
+			 * If we have a share check context and a reference for
+			 * another inode, we can't exit immediately. This is
+			 * because even if this is a BTRFS_ADD_DELAYED_REF
+			 * reference we may find next a BTRFS_DROP_DELAYED_REF
+			 * which cancels out this ADD reference.
+			 *
+			 * If this is a DROP reference and there was no previous
+			 * ADD reference, then we need to signal that when we
+			 * process references from the extent tree (through
+			 * add_inline_refs() and add_keyed_refs()), we should
+			 * not exit early if we find a reference for another
+			 * inode, because one of the delayed DROP references
+			 * may cancel that reference in the extent tree.
 			 */
-			if (sc && sc->inum && ref->objectid != sc->inum) {
-				ret = BACKREF_FOUND_SHARED;
-				goto out;
-			}
+			if (sc && count < 0)
+				sc->have_delayed_delete_refs = true;
 
 			ret = add_indirect_ref(fs_info, preftrees, ref->root,
 					       &key, 0, node->bytenr, count, sc,
@@ -920,7 +949,7 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
 	}
 	if (!ret)
 		ret = extent_is_shared(sc);
-out:
+
 	spin_unlock(&head->lock);
 	return ret;
 }
@@ -1023,7 +1052,8 @@ static int add_inline_refs(const struct btrfs_fs_info *fs_info,
 			key.type = BTRFS_EXTENT_DATA_KEY;
 			key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 
-			if (sc && sc->inum && key.objectid != sc->inum) {
+			if (sc && sc->inum && key.objectid != sc->inum &&
+			    !sc->have_delayed_delete_refs) {
 				ret = BACKREF_FOUND_SHARED;
 				break;
 			}
@@ -1033,6 +1063,7 @@ static int add_inline_refs(const struct btrfs_fs_info *fs_info,
 			ret = add_indirect_ref(fs_info, preftrees, root,
 					       &key, 0, bytenr, count,
 					       sc, GFP_NOFS);
+
 			break;
 		}
 		default:
@@ -1122,7 +1153,8 @@ static int add_keyed_refs(struct btrfs_root *extent_root,
 			key.type = BTRFS_EXTENT_DATA_KEY;
 			key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 
-			if (sc && sc->inum && key.objectid != sc->inum) {
+			if (sc && sc->inum && key.objectid != sc->inum &&
+			    !sc->have_delayed_delete_refs) {
 				ret = BACKREF_FOUND_SHARED;
 				break;
 			}
@@ -1354,6 +1386,12 @@ again:
 				if (ret < 0)
 					goto out;
 				ref->inode_list = eie;
+				/*
+				 * We transferred the list ownership to the ref,
+				 * so set to NULL to avoid a double free in case
+				 * an error happens after this.
+				 */
+				eie = NULL;
 			}
 			ret = ulist_add_merge_ptr(refs, ref->parent,
 						  ref->inode_list,
@@ -1379,6 +1417,14 @@ again:
 				eie->next = ref->inode_list;
 			}
 			eie = NULL;
+			/*
+			 * We have transferred the inode list ownership from
+			 * this ref to the ref we added to the 'refs' ulist.
+			 * So set this ref's inode list to NULL to avoid
+			 * use-after-free when our caller uses it or double
+			 * frees in case an error happens before we return.
+			 */
+			ref->inode_list = NULL;
 		}
 		cond_resched();
 	}
@@ -1395,24 +1441,6 @@ out:
 	return ret;
 }
 
-static void free_leaf_list(struct ulist *blocks)
-{
-	struct ulist_node *node = NULL;
-	struct extent_inode_elem *eie;
-	struct ulist_iterator uiter;
-
-	ULIST_ITER_INIT(&uiter);
-	while ((node = ulist_next(blocks, &uiter))) {
-		if (!node->aux)
-			continue;
-		eie = unode_aux_to_inode_list(node);
-		free_inode_elem_list(eie);
-		node->aux = 0;
-	}
-
-	ulist_free(blocks);
-}
-
 /*
  * Finds all leafs with a reference to the specified combination of bytenr and
  * offset. key_list_head will point to a list of corresponding keys (caller must
@@ -1522,6 +1550,9 @@ static bool lookup_backref_shared_cache(struct btrfs_backref_shared_cache *cache
 {
 	struct btrfs_backref_shared_cache_entry *entry;
 
+	if (!cache->use_cache)
+		return false;
+
 	if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
 		return false;
 
@@ -1557,6 +1588,19 @@ static bool lookup_backref_shared_cache(struct btrfs_backref_shared_cache *cache
 		return false;
 
 	*is_shared = entry->is_shared;
+	/*
+	 * If the node at this level is shared, than all nodes below are also
+	 * shared. Currently some of the nodes below may be marked as not shared
+	 * because we have just switched from one leaf to another, and switched
+	 * also other nodes above the leaf and below the current level, so mark
+	 * them as shared.
+	 */
+	if (*is_shared) {
+		for (int i = 0; i < level; i++) {
+			cache->entries[i].is_shared = true;
+			cache->entries[i].gen = entry->gen;
+		}
+	}
 
 	return true;
 }
@@ -1573,6 +1617,9 @@ static void store_backref_shared_cache(struct btrfs_backref_shared_cache *cache,
 	struct btrfs_backref_shared_cache_entry *entry;
 	u64 gen;
 
+	if (!cache->use_cache)
+		return;
+
 	if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
 		return;
 
@@ -1648,6 +1695,7 @@ int btrfs_is_data_extent_shared(struct btrfs_root *root, u64 inum, u64 bytenr,
 		.root_objectid = root->root_key.objectid,
 		.inum = inum,
 		.share_count = 0,
+		.have_delayed_delete_refs = false,
 	};
 	int level;
 
@@ -1669,6 +1717,7 @@ int btrfs_is_data_extent_shared(struct btrfs_root *root, u64 inum, u64 bytenr,
 	/* -1 means we are in the bytenr of the data extent. */
 	level = -1;
 	ULIST_ITER_INIT(&uiter);
+	cache->use_cache = true;
 	while (1) {
 		bool is_shared;
 		bool cached;
@@ -1698,6 +1747,24 @@ int btrfs_is_data_extent_shared(struct btrfs_root *root, u64 inum, u64 bytenr,
 		    extent_gen > btrfs_root_last_snapshot(&root->root_item))
 			break;
 
+		/*
+		 * If our data extent was not directly shared (without multiple
+		 * reference items), than it might have a single reference item
+		 * with a count > 1 for the same offset, which means there are 2
+		 * (or more) file extent items that point to the data extent -
+		 * this happens when a file extent item needs to be split and
+		 * then one item gets moved to another leaf due to a b+tree leaf
+		 * split when inserting some item. In this case the file extent
+		 * items may be located in different leaves and therefore some
+		 * of the leaves may be referenced through shared subtrees while
+		 * others are not. Since our extent buffer cache only works for
+		 * a single path (by far the most common case and simpler to
+		 * deal with), we can not use it if we have multiple leaves
+		 * (which implies multiple paths).
+		 */
+		if (level == -1 && tmp->nnodes > 1)
+			cache->use_cache = false;
+
 		if (level >= 0)
 			store_backref_shared_cache(cache, root, bytenr,
 						   level, false);
@@ -1713,6 +1780,7 @@ int btrfs_is_data_extent_shared(struct btrfs_root *root, u64 inum, u64 bytenr,
 			break;
 		}
 		shared.share_count = 0;
+		shared.have_delayed_delete_refs = false;
 		cond_resched();
 	}