btrfs: reloc: add backref_cache::pending_edge and backref_cache::useless_node

These two new members will act the same as the existing local lists,
@useless and @list in build_backref_tree().

Currently build_backref_tree() is only executed serially, thus moving
such local list into backref_cache is still safe.

Also since we're here, use list_first_entry() to replace a lot of
list_entry() calls after !list_empty().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index a8b5ea5..39294c5 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -158,6 +158,12 @@ struct backref_cache {
 
        int nr_nodes;
        int nr_edges;
+
+       /* The list of unchecked backref edges during backref cache build */
+       struct list_head pending_edge;
+
+       /* The list of useless backref nodes during backref cache build */
+       struct list_head useless_node;
 };
 
 /*
@@ -269,6 +275,8 @@ static void backref_cache_init(struct backref_cache *cache)
        INIT_LIST_HEAD(&cache->changed);
        INIT_LIST_HEAD(&cache->detached);
        INIT_LIST_HEAD(&cache->leaves);
+       INIT_LIST_HEAD(&cache->pending_edge);
+       INIT_LIST_HEAD(&cache->useless_node);
 }
 
 static void backref_cache_cleanup(struct backref_cache *cache)
@@ -292,6 +300,8 @@ static void backref_cache_cleanup(struct backref_cache *cache)
 
        for (i = 0; i < BTRFS_MAX_LEVEL; i++)
                ASSERT(list_empty(&cache->pending[i]));
+       ASSERT(list_empty(&cache->pending_edge));
+       ASSERT(list_empty(&cache->useless_node));
        ASSERT(list_empty(&cache->changed));
        ASSERT(list_empty(&cache->detached));
        ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
@@ -699,8 +709,6 @@ struct backref_node *build_backref_tree(struct reloc_control *rc,
        struct backref_node *exist = NULL;
        struct backref_edge *edge;
        struct rb_node *rb_node;
-       LIST_HEAD(list); /* Pending edge list, upper node needs to be checked */
-       LIST_HEAD(useless);
        int cowonly;
        int ret;
        int err = 0;
@@ -764,7 +772,7 @@ again:
                 * check its backrefs
                 */
                if (!exist->checked)
-                       list_add_tail(&edge->list[UPPER], &list);
+                       list_add_tail(&edge->list[UPPER], &cache->pending_edge);
        } else {
                exist = NULL;
        }
@@ -842,7 +850,8 @@ again:
                                 *  backrefs for the upper level block isn't
                                 *  cached, add the block to pending list
                                 */
-                               list_add_tail(&edge->list[UPPER], &list);
+                               list_add_tail(&edge->list[UPPER],
+                                             &cache->pending_edge);
                        } else {
                                upper = rb_entry(rb_node, struct backref_node,
                                                 rb_node);
@@ -884,7 +893,7 @@ again:
                               cur->bytenr);
                        if (should_ignore_root(root)) {
                                btrfs_put_root(root);
-                               list_add(&cur->list, &useless);
+                               list_add(&cur->list, &cache->useless_node);
                        } else {
                                cur->root = root;
                        }
@@ -930,7 +939,8 @@ again:
                                       lower->bytenr);
                                if (should_ignore_root(root)) {
                                        btrfs_put_root(root);
-                                       list_add(&lower->list, &useless);
+                                       list_add(&lower->list,
+                                                &cache->useless_node);
                                } else {
                                        lower->root = root;
                                }
@@ -979,7 +989,7 @@ again:
                                if (!upper->checked && need_check) {
                                        need_check = false;
                                        list_add_tail(&edge->list[UPPER],
-                                                     &list);
+                                                     &cache->pending_edge);
                                } else {
                                        if (upper->checked)
                                                need_check = true;
@@ -1017,8 +1027,9 @@ again:
        WARN_ON(exist);
 
        /* the pending list isn't empty, take the first block to process */
-       if (!list_empty(&list)) {
-               edge = list_entry(list.next, struct backref_edge, list[UPPER]);
+       if (!list_empty(&cache->pending_edge)) {
+               edge = list_first_entry(&cache->pending_edge,
+                                 struct backref_edge, list[UPPER]);
                list_del_init(&edge->list[UPPER]);
                cur = edge->node[UPPER];
                goto again;
@@ -1039,10 +1050,11 @@ again:
        }
 
        list_for_each_entry(edge, &node->upper, list[LOWER])
-               list_add_tail(&edge->list[UPPER], &list);
+               list_add_tail(&edge->list[UPPER], &cache->pending_edge);
 
-       while (!list_empty(&list)) {
-               edge = list_entry(list.next, struct backref_edge, list[UPPER]);
+       while (!list_empty(&cache->pending_edge)) {
+               edge = list_first_entry(&cache->pending_edge,
+                               struct backref_edge, list[UPPER]);
                list_del_init(&edge->list[UPPER]);
                upper = edge->node[UPPER];
                if (upper->detached) {
@@ -1050,7 +1062,7 @@ again:
                        lower = edge->node[LOWER];
                        free_backref_edge(cache, edge);
                        if (list_empty(&lower->upper))
-                               list_add(&lower->list, &useless);
+                               list_add(&lower->list, &cache->useless_node);
                        continue;
                }
 
@@ -1090,7 +1102,7 @@ again:
                list_add_tail(&edge->list[UPPER], &upper->lower);
 
                list_for_each_entry(edge, &upper->upper, list[LOWER])
-                       list_add_tail(&edge->list[UPPER], &list);
+                       list_add_tail(&edge->list[UPPER], &cache->pending_edge);
        }
        /*
         * process useless backref nodes. backref nodes for tree leaves
@@ -1098,8 +1110,9 @@ again:
         * tree blocks are left in the cache to avoid unnecessary backref
         * lookup.
         */
-       while (!list_empty(&useless)) {
-               upper = list_entry(useless.next, struct backref_node, list);
+       while (!list_empty(&cache->useless_node)) {
+               upper = list_first_entry(&cache->useless_node,
+                                  struct backref_node, list);
                list_del_init(&upper->list);
                ASSERT(list_empty(&upper->upper));
                if (upper == node)
@@ -1109,7 +1122,7 @@ again:
                        upper->lowest = 0;
                }
                while (!list_empty(&upper->lower)) {
-                       edge = list_entry(upper->lower.next,
+                       edge = list_first_entry(&upper->lower,
                                          struct backref_edge, list[UPPER]);
                        list_del(&edge->list[UPPER]);
                        list_del(&edge->list[LOWER]);
@@ -1117,7 +1130,7 @@ again:
                        free_backref_edge(cache, edge);
 
                        if (list_empty(&lower->upper))
-                               list_add(&lower->list, &useless);
+                               list_add(&lower->list, &cache->useless_node);
                }
                mark_block_processed(rc, upper);
                if (upper->level > 0) {
@@ -1132,14 +1145,14 @@ out:
        btrfs_backref_iter_free(iter);
        btrfs_free_path(path);
        if (err) {
-               while (!list_empty(&useless)) {
-                       lower = list_entry(useless.next,
+               while (!list_empty(&cache->useless_node)) {
+                       lower = list_first_entry(&cache->useless_node,
                                           struct backref_node, list);
                        list_del_init(&lower->list);
                }
-               while (!list_empty(&list)) {
-                       edge = list_first_entry(&list, struct backref_edge,
-                                               list[UPPER]);
+               while (!list_empty(&cache->pending_edge)) {
+                       edge = list_first_entry(&cache->pending_edge,
+                                       struct backref_edge, list[UPPER]);
                        list_del(&edge->list[UPPER]);
                        list_del(&edge->list[LOWER]);
                        lower = edge->node[LOWER];
@@ -1152,20 +1165,21 @@ out:
                         */
                        if (list_empty(&lower->upper) &&
                            RB_EMPTY_NODE(&lower->rb_node))
-                               list_add(&lower->list, &useless);
+                               list_add(&lower->list, &cache->useless_node);
 
                        if (!RB_EMPTY_NODE(&upper->rb_node))
                                continue;
 
                        /* Add this guy's upper edges to the list to process */
                        list_for_each_entry(edge, &upper->upper, list[LOWER])
-                               list_add_tail(&edge->list[UPPER], &list);
+                               list_add_tail(&edge->list[UPPER],
+                                             &cache->pending_edge);
                        if (list_empty(&upper->upper))
-                               list_add(&upper->list, &useless);
+                               list_add(&upper->list, &cache->useless_node);
                }
 
-               while (!list_empty(&useless)) {
-                       lower = list_entry(useless.next,
+               while (!list_empty(&cache->useless_node)) {
+                       lower = list_first_entry(&cache->useless_node,
                                           struct backref_node, list);
                        list_del_init(&lower->list);
                        if (lower == node)
@@ -1174,9 +1188,13 @@ out:
                }
 
                remove_backref_node(cache, node);
+               ASSERT(list_empty(&cache->useless_node) &&
+                      list_empty(&cache->pending_edge));
                return ERR_PTR(err);
        }
        ASSERT(!node || !node->detached);
+       ASSERT(list_empty(&cache->useless_node) &&
+              list_empty(&cache->pending_edge));
        return node;
 }