Btrfs: do not reuse objectid of deleted snapshot/subvol

The new back reference format does not allow reusing objectid of
deleted snapshot/subvol. So we use ++highest_objectid to allocate
objectid for new snapshot/subvol.

Now we use ++highest_objectid to allocate objectid for both new inode
and new snapshot/subvolume, so this patch removes 'find hole' code in
btrfs_find_free_objectid.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 15 insertions, 78 deletions

diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 9abbced1123d..c56eb5909172 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -43,9 +43,10 @@ int btrfs_find_highest_inode(struct btrfs_root *root, u64 *objectid)
                 slot = path->slots[0] - 1;
                 l = path->nodes[0];
                 btrfs_item_key_to_cpu(l, &found_key, slot);
-                *objectid = found_key.objectid;
+                *objectid = max_t(u64, found_key.objectid,
+                                  BTRFS_FIRST_FREE_OBJECTID - 1);
         } else {
-                *objectid = BTRFS_FIRST_FREE_OBJECTID;
+                *objectid = BTRFS_FIRST_FREE_OBJECTID - 1;
         }
         ret = 0;
 error:
@@ -53,91 +54,27 @@ error:
         return ret;
 }
 
-/*
- * walks the btree of allocated inodes and find a hole.
- */
 int btrfs_find_free_objectid(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              u64 dirid, u64 *objectid)
 {
-        struct btrfs_path *path;
-        struct btrfs_key key;
         int ret;
-        int slot = 0;
-        u64 last_ino = 0;
-        int start_found;
-        struct extent_buffer *l;
-        struct btrfs_key search_key;
-        u64 search_start = dirid;
-
         mutex_lock(&root->objectid_mutex);
-        if (root->last_inode_alloc >= BTRFS_FIRST_FREE_OBJECTID &&
-            root->last_inode_alloc < BTRFS_LAST_FREE_OBJECTID) {
-                *objectid = ++root->last_inode_alloc;
-                mutex_unlock(&root->objectid_mutex);
-                return 0;
-        }
-        path = btrfs_alloc_path();
-        BUG_ON(!path);
-        search_start = max(search_start, (u64)BTRFS_FIRST_FREE_OBJECTID);
-        search_key.objectid = search_start;
-        search_key.type = 0;
-        search_key.offset = 0;
-
-        start_found = 0;
-        ret = btrfs_search_slot(trans, root, &search_key, path, 0, 0);
-        if (ret < 0)
-                goto error;
 
-        while (1) {
-                l = path->nodes[0];
-                slot = path->slots[0];
-                if (slot >= btrfs_header_nritems(l)) {
-                        ret = btrfs_next_leaf(root, path);
-                        if (ret == 0)
-                                continue;
-                        if (ret < 0)
-                                goto error;
-                        if (!start_found) {
-                                *objectid = search_start;
-                                start_found = 1;
-                                goto found;
-                        }
-                        *objectid = last_ino > search_start ?
-                                last_ino : search_start;
-                        goto found;
-                }
-                btrfs_item_key_to_cpu(l, &key, slot);
-                if (key.objectid >= search_start) {
-                        if (start_found) {
-                                if (last_ino < search_start)
-                                        last_ino = search_start;
-                                if (key.objectid > last_ino) {
-                                        *objectid = last_ino;
-                                        goto found;
-                                }
-                        } else if (key.objectid > search_start) {
-                                *objectid = search_start;
-                                goto found;
-                        }
-                }
-                if (key.objectid >= BTRFS_LAST_FREE_OBJECTID)
-                        break;
+        if (unlikely(root->highest_objectid < BTRFS_FIRST_FREE_OBJECTID)) {
+                ret = btrfs_find_highest_inode(root, &root->highest_objectid);
+                if (ret)
+                        goto out;
+        }
 
-                start_found = 1;
-                last_ino = key.objectid + 1;
-                path->slots[0]++;
+        if (unlikely(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
+                ret = -ENOSPC;
+                goto out;
         }
-        BUG_ON(1);
-found:
-        btrfs_release_path(root, path);
-        btrfs_free_path(path);
-        BUG_ON(*objectid < search_start);
-        mutex_unlock(&root->objectid_mutex);
-        return 0;
-error:
-        btrfs_release_path(root, path);
-        btrfs_free_path(path);
+
+        *objectid = ++root->highest_objectid;
+        ret = 0;
+out:
         mutex_unlock(&root->objectid_mutex);
         return ret;
 }