Btrfs: setup free ino caching in a more asynchronous way

For a filesystem that has lots of files in it, the first time we mount
it with free ino caching support, it can take quite a long time to
setup the caching before we can create new files.

Here we fill the cache with [highest_ino, BTRFS_LAST_FREE_OBJECTID]
before we start the caching thread to search through the extent tree.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 0009705..3262cd1 100644 (file)
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -60,12 +60,12 @@ again:
 
        while (1) {
                smp_mb();
-               if (fs_info->closing > 1)
+               if (fs_info->closing)
                        goto out;
 
                leaf = path->nodes[0];
                slot = path->slots[0];
-               if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+               if (slot >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto out;
@@ -100,7 +100,7 @@ again:
                if (key.type != BTRFS_INODE_ITEM_KEY)
                        goto next;
 
-               if (key.objectid >= BTRFS_LAST_FREE_OBJECTID)
+               if (key.objectid >= root->highest_objectid)
                        break;
 
                if (last != (u64)-1 && last + 1 != key.objectid) {
@@ -114,9 +114,9 @@ next:
                path->slots[0]++;
        }
 
-       if (last < BTRFS_LAST_FREE_OBJECTID - 1) {
+       if (last < root->highest_objectid - 1) {
                __btrfs_add_free_space(ctl, last + 1,
-                                      BTRFS_LAST_FREE_OBJECTID - last - 1);
+                                      root->highest_objectid - last - 1);
        }
 
        spin_lock(&root->cache_lock);
@@ -136,8 +136,10 @@ out:
 
 static void start_caching(struct btrfs_root *root)
 {
+       struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
        struct task_struct *tsk;
        int ret;
+       u64 objectid;
 
        spin_lock(&root->cache_lock);
        if (root->cached != BTRFS_CACHE_NO) {
@@ -156,6 +158,19 @@ static void start_caching(struct btrfs_root *root)
                return;
        }
 
+       /*
+        * It can be quite time-consuming to fill the cache by searching
+        * through the extent tree, and this can keep ino allocation path
+        * waiting. Therefore at start we quickly find out the highest
+        * inode number and we know we can use inode numbers which fall in
+        * [highest_ino + 1, BTRFS_LAST_FREE_OBJECTID].
+        */
+       ret = btrfs_find_free_objectid(root, &objectid);
+       if (!ret && objectid <= BTRFS_LAST_FREE_OBJECTID) {
+               __btrfs_add_free_space(ctl, objectid,
+                                      BTRFS_LAST_FREE_OBJECTID - objectid + 1);
+       }
+
        tsk = kthread_run(caching_kthread, root, "btrfs-ino-cache-%llu\n",
                          root->root_key.objectid);
        BUG_ON(IS_ERR(tsk));
@@ -209,7 +224,8 @@ again:
 
                start_caching(root);
 
-               if (objectid <= root->cache_progress)
+               if (objectid <= root->cache_progress ||
+                   objectid > root->highest_objectid)
                        __btrfs_add_free_space(ctl, objectid, 1);
                else
                        __btrfs_add_free_space(pinned, objectid, 1);