btrfs-progs: backref: use separate list for missing keys

Rather than iterate over all outstanding backrefs to resolve missing keys,
use a separate list that only contains refs that need missing keys resolved.

Once the missing key is resolved, move the ref to the pending list.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/backref.c b/backref.c
index 305cd05..b63a009 100644 (file)
--- a/backref.c
+++ b/backref.c
@@ -137,11 +137,13 @@ static struct __prelim_ref *list_first_pref(struct list_head *head)
 
 struct pref_state {
        struct list_head pending;
+       struct list_head pending_missing_keys;
 };
 
 static void init_pref_state(struct pref_state *prefstate)
 {
        INIT_LIST_HEAD(&prefstate->pending);
+       INIT_LIST_HEAD(&prefstate->pending_missing_keys);
 }
 
 /*
@@ -188,7 +190,7 @@ static int __add_prelim_ref(struct pref_state *prefstate, u64 root_id,
                            u64 parent, u64 wanted_disk_byte, int count,
                            gfp_t gfp_mask)
 {
-       struct list_head *head = &prefstate->pending;
+       struct list_head *head;
        struct __prelim_ref *ref;
 
        if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
@@ -199,16 +201,20 @@ static int __add_prelim_ref(struct pref_state *prefstate, u64 root_id,
                return -ENOMEM;
 
        ref->root_id = root_id;
-       if (key)
+       if (key) {
                ref->key_for_search = *key;
-       else
+               head = &prefstate->pending;
+       } else {
                memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
+               head = &prefstate->pending_missing_keys;
+       }
 
        ref->inode_list = NULL;
        ref->level = level;
        ref->count = count;
        ref->parent = parent;
        ref->wanted_disk_byte = wanted_disk_byte;
+
        list_add_tail(&ref->list, head);
 
        return 0;
@@ -454,18 +460,16 @@ static inline int ref_for_same_block(struct __prelim_ref *ref1,
 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
                              struct pref_state *prefstate)
 {
-       struct list_head *head = &prefstate->pending;
-       struct list_head *pos;
        struct extent_buffer *eb;
 
-       list_for_each(pos, head) {
+       while (!list_empty(&prefstate->pending_missing_keys)) {
                struct __prelim_ref *ref;
-               ref = list_entry(pos, struct __prelim_ref, list);
 
-               if (ref->parent)
-                       continue;
-               if (ref->key_for_search.type)
-                       continue;
+               ref = list_first_pref(&prefstate->pending_missing_keys);
+
+               ASSERT(ref->root_id);
+               ASSERT(!ref->parent);
+               ASSERT(ref->key_for_search.type);
                BUG_ON(!ref->wanted_disk_byte);
                eb = read_tree_block(fs_info, ref->wanted_disk_byte, 0);
                if (!extent_buffer_uptodate(eb)) {
@@ -477,6 +481,7 @@ static int __add_missing_keys(struct btrfs_fs_info *fs_info,
                else
                        btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
                free_extent_buffer(eb);
+               list_move(&ref->list, &prefstate->pending);
        }
        return 0;
 }
@@ -807,6 +812,8 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 
        __merge_refs(&prefstate, 2);
 
+       BUG_ON(!list_empty(&prefstate.pending_missing_keys));
+
        while (!list_empty(&prefstate.pending)) {
                ref = list_first_pref(&prefstate.pending);
                WARN_ON(ref->count < 0);