From 1f872924663f9a15924cc7169932608c1d697ee1 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Tue, 25 Feb 2020 14:20:13 +0800 Subject: [PATCH] btrfs: reloc: refactor finishing part of upper linkage into finish_upper_links() After handle_one_tree_backref(), all newly added (not cached) edges and nodes have the following features: - Only backref_edge::list[LOWER] is linked. This means, we can only iterate from botton to top, not the other direction. - Newly added nodes are not added to cache rb_tree yet So to finish the backref cache, we still need to finish the links and add all nodes into backref cache rb_tree. This patch will refactor the existing code into finish_upper_links(), add more comments of each branch, and why we need to do all the work. Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/relocation.c | 186 +++++++++++++++++++++++++++++++------------------- 1 file changed, 117 insertions(+), 69 deletions(-) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index ad94482..29d5340 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -1081,6 +1081,118 @@ out: } /* + * In handle_one_tree_backref(), we have only linked the lower node to the edge, + * but the upper node hasn't been linked to the edge. + * This means we can only iterate through backref_node::upper to reach parent + * edges, but not through backref_node::lower to reach children edges. + * + * This function will finish the backref_node::lower to related edges, so that + * backref cache can be bi-directionally iterated. + * + * Also, this will add the nodes to backref cache for the next run. + */ +static int finish_upper_links(struct backref_cache *cache, + struct backref_node *start) +{ + struct list_head *useless_node = &cache->useless_node; + struct backref_edge *edge; + struct rb_node *rb_node; + LIST_HEAD(pending_edge); + + ASSERT(start->checked); + + /* Insert this node to cache if it's not COW-only */ + if (!start->cowonly) { + rb_node = tree_insert(&cache->rb_root, start->bytenr, + &start->rb_node); + if (rb_node) + backref_tree_panic(rb_node, -EEXIST, start->bytenr); + list_add_tail(&start->lower, &cache->leaves); + } + + /* + * Use breadth first search to iterate all related edges. + * + * The starting points are all the edges of this node + */ + list_for_each_entry(edge, &start->upper, list[LOWER]) + list_add_tail(&edge->list[UPPER], &pending_edge); + + while (!list_empty(&pending_edge)) { + struct backref_node *upper; + struct backref_node *lower; + struct rb_node *rb_node; + + edge = list_first_entry(&pending_edge, struct backref_edge, + list[UPPER]); + list_del_init(&edge->list[UPPER]); + upper = edge->node[UPPER]; + lower = edge->node[LOWER]; + + /* Parent is detached, no need to keep any edges */ + if (upper->detached) { + list_del(&edge->list[LOWER]); + free_backref_edge(cache, edge); + + /* Lower node is orphan, queue for cleanup */ + if (list_empty(&lower->upper)) + list_add(&lower->list, useless_node); + continue; + } + + /* + * All new nodes added in current build_backref_tree() haven't + * been linked to the cache rb tree. + * So if we have upper->rb_node populated, this means a cache + * hit. We only need to link the edge, as @upper and all its + * parent have already been linked. + */ + if (!RB_EMPTY_NODE(&upper->rb_node)) { + if (upper->lowest) { + list_del_init(&upper->lower); + upper->lowest = 0; + } + + list_add_tail(&edge->list[UPPER], &upper->lower); + continue; + } + + /* Sanity check, we shouldn't have any unchecked nodes */ + if (!upper->checked) { + ASSERT(0); + return -EUCLEAN; + } + + /* Sanity check, COW-only node has non-COW-only parent */ + if (start->cowonly != upper->cowonly) { + ASSERT(0); + return -EUCLEAN; + } + + /* Only cache non-COW-only (subvolume trees) tree blocks */ + if (!upper->cowonly) { + rb_node = tree_insert(&cache->rb_root, upper->bytenr, + &upper->rb_node); + if (rb_node) { + backref_tree_panic(rb_node, -EEXIST, + upper->bytenr); + return -EUCLEAN; + } + } + + list_add_tail(&edge->list[UPPER], &upper->lower); + + /* + * Also queue all the parent edges of this uncached node to + * finish the upper linkage + */ + list_for_each_entry(edge, &upper->upper, list[LOWER]) + list_add_tail(&edge->list[UPPER], &pending_edge); + } + return 0; +} + +/* * Build backref tree for a given tree block. Root of the backref tree * corresponds the tree block, leaves of the backref tree correspond roots of * b-trees that reference the tree block. @@ -1107,8 +1219,6 @@ static noinline_for_stack struct backref_node *build_backref_tree( struct backref_node *lower; struct backref_node *node = NULL; struct backref_edge *edge; - struct rb_node *rb_node; - int cowonly; int ret; int err = 0; @@ -1149,75 +1259,13 @@ static noinline_for_stack struct backref_node *build_backref_tree( } } while (edge); - /* - * everything goes well, connect backref nodes and insert backref nodes - * into the cache. - */ - ASSERT(node->checked); - cowonly = node->cowonly; - if (!cowonly) { - rb_node = tree_insert(&cache->rb_root, node->bytenr, - &node->rb_node); - if (rb_node) - backref_tree_panic(rb_node, -EEXIST, node->bytenr); - list_add_tail(&node->lower, &cache->leaves); + /* Finish the upper linkage of newly added edges/nodes */ + ret = finish_upper_links(cache, node); + if (ret < 0) { + err = ret; + goto out; } - list_for_each_entry(edge, &node->upper, list[LOWER]) - list_add_tail(&edge->list[UPPER], &cache->pending_edge); - - 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) { - list_del(&edge->list[LOWER]); - lower = edge->node[LOWER]; - free_backref_edge(cache, edge); - if (list_empty(&lower->upper)) - list_add(&lower->list, &cache->useless_node); - continue; - } - - if (!RB_EMPTY_NODE(&upper->rb_node)) { - if (upper->lowest) { - list_del_init(&upper->lower); - upper->lowest = 0; - } - - list_add_tail(&edge->list[UPPER], &upper->lower); - continue; - } - - if (!upper->checked) { - /* - * Still want to blow up for developers since this is a - * logic bug. - */ - ASSERT(0); - err = -EINVAL; - goto out; - } - if (cowonly != upper->cowonly) { - ASSERT(0); - err = -EINVAL; - goto out; - } - - if (!cowonly) { - rb_node = tree_insert(&cache->rb_root, upper->bytenr, - &upper->rb_node); - if (rb_node) - backref_tree_panic(rb_node, -EEXIST, - upper->bytenr); - } - - list_add_tail(&edge->list[UPPER], &upper->lower); - - list_for_each_entry(edge, &upper->upper, list[LOWER]) - list_add_tail(&edge->list[UPPER], &cache->pending_edge); - } /* * process useless backref nodes. backref nodes for tree leaves * are deleted from the cache. backref nodes for upper level -- 2.7.4