@@ -1921,8 +1921,7 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
level = -1;
ULIST_ITER_INIT(&uiter);
while (1) {
- bool is_shared;
- bool cached;
+ const unsigned long prev_ref_count = ctx->refs.nnodes;
walk_ctx.bytenr = bytenr;
ret = find_parent_nodes(&walk_ctx, &shared);
@@ -1940,21 +1939,36 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
ret = 0;
/*
- * 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).
+ * More than one extent buffer (bytenr) may have been added to
+ * the ctx->refs ulist, in which case we have to check multiple
+ * tree paths in case the first one is not shared, so we can not
+ * use the path cache which is made for a single path. Multiple
+ * extent buffers at the current level happen when:
+ *
+ * 1) level -1, the data extent: If our data extent was not
+ * directly shared (without multiple reference items), then
+ * 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).
+ *
+ * 2) level >= 0, a tree node/leaf: We can have a mix of direct
+ * and indirect references on a b+tree node/leaf, so we have
+ * to check multiple paths, and the extent buffer (the
+ * current bytenr) may be shared or not. One example is
+ * during relocation as we may get a shared tree block ref
+ * (direct ref) and a non-shared tree block ref (indirect
+ * ref) for the same node/leaf.
*/
- if (level == -1 && ctx->refs.nnodes > 1)
+ if ((ctx->refs.nnodes - prev_ref_count) > 1)
ctx->use_path_cache = false;
if (level >= 0)
@@ -1964,18 +1978,45 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
if (!node)
break;
bytenr = node->val;
- level++;
- cached = lookup_backref_shared_cache(ctx, root, bytenr, level,
- &is_shared);
- if (cached) {
- ret = (is_shared ? 1 : 0);
- break;
+ if (ctx->use_path_cache) {
+ bool is_shared;
+ bool cached;
+
+ level++;
+ cached = lookup_backref_shared_cache(ctx, root, bytenr,
+ level, &is_shared);
+ if (cached) {
+ ret = (is_shared ? 1 : 0);
+ break;
+ }
}
shared.share_count = 0;
shared.have_delayed_delete_refs = false;
cond_resched();
}
+ /*
+ * If the path cache is disabled, then it means at some tree level we
+ * got multiple parents due to a mix of direct and indirect backrefs or
+ * multiple leaves with file extent items pointing to the same data
+ * extent. We have to invalidate the cache and cache only the sharedness
+ * result for the levels where we got only one node/reference.
+ */
+ if (!ctx->use_path_cache) {
+ int i = 0;
+
+ level--;
+ if (ret >= 0 && level >= 0) {
+ bytenr = ctx->path_cache_entries[level].bytenr;
+ ctx->use_path_cache = true;
+ store_backref_shared_cache(ctx, root, bytenr, level, ret);
+ i = level + 1;
+ }
+
+ for ( ; i < BTRFS_MAX_LEVEL; i++)
+ ctx->path_cache_entries[i].bytenr = 0;
+ }
+
/*
* Cache the sharedness result for the data extent if we know our inode
* has more than 1 file extent item that refers to the data extent.