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>

6 files changed, 31 insertions, 116 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3b6df7140575..746a9acd2189 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1007,8 +1007,8 @@ struct btrfs_root {
         u32 stripesize;
 
         u32 type;
-        u64 highest_inode;
-        u64 last_inode_alloc;
+
+        u64 highest_objectid;
         int ref_cows;
         int track_dirty;
         u64 defrag_trans_start;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 16dae122dda4..790f4b61a3d7 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -895,8 +895,7 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
         root->fs_info = fs_info;
         root->objectid = objectid;
         root->last_trans = 0;
-        root->highest_inode = 0;
-        root->last_inode_alloc = 0;
+        root->highest_objectid = 0;
         root->name = NULL;
         root->in_sysfs = 0;
         root->inode_tree.rb_node = NULL;
@@ -1095,7 +1094,6 @@ struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
         struct btrfs_fs_info *fs_info = tree_root->fs_info;
         struct btrfs_path *path;
         struct extent_buffer *l;
-        u64 highest_inode;
         u64 generation;
         u32 blocksize;
         int ret = 0;
@@ -1110,7 +1108,7 @@ struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
                         kfree(root);
                         return ERR_PTR(ret);
                 }
-                goto insert;
+                goto out;
         }
 
         __setup_root(tree_root->nodesize, tree_root->leafsize,
@@ -1120,39 +1118,30 @@ struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
         path = btrfs_alloc_path();
         BUG_ON(!path);
         ret = btrfs_search_slot(NULL, tree_root, location, path, 0, 0);
-        if (ret != 0) {
-                if (ret > 0)
-                        ret = -ENOENT;
-                goto out;
+        if (ret == 0) {
+                l = path->nodes[0];
+                read_extent_buffer(l, &root->root_item,
+                                btrfs_item_ptr_offset(l, path->slots[0]),
+                                sizeof(root->root_item));
+                memcpy(&root->root_key, location, sizeof(*location));
         }
-        l = path->nodes[0];
-        read_extent_buffer(l, &root->root_item,
-               btrfs_item_ptr_offset(l, path->slots[0]),
-               sizeof(root->root_item));
-        memcpy(&root->root_key, location, sizeof(*location));
-        ret = 0;
-out:
-        btrfs_release_path(root, path);
         btrfs_free_path(path);
         if (ret) {
-                kfree(root);
+                if (ret > 0)
+                        ret = -ENOENT;
                 return ERR_PTR(ret);
         }
+
         generation = btrfs_root_generation(&root->root_item);
         blocksize = btrfs_level_size(root, btrfs_root_level(&root->root_item));
         root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),
                                      blocksize, generation);
         root->commit_root = btrfs_root_node(root);
         BUG_ON(!root->node);
-insert:
-        if (location->objectid != BTRFS_TREE_LOG_OBJECTID) {
+out:
+        if (location->objectid != BTRFS_TREE_LOG_OBJECTID)
                 root->ref_cows = 1;
-                ret = btrfs_find_highest_inode(root, &highest_inode);
-                if (ret == 0) {
-                        root->highest_inode = highest_inode;
-                        root->last_inode_alloc = highest_inode;
-                }
-        }
+
         return root;
 }
 
diff --git a/fs/btrfs/inode-item.c b/fs/btrfs/inode-item.c
index 6b627c611808..fc6f4a7f6405 100644
--- a/fs/btrfs/inode-item.c
+++ b/fs/btrfs/inode-item.c
@@ -177,8 +177,6 @@ int btrfs_insert_empty_inode(struct btrfs_trans_handle *trans,
 
         ret = btrfs_insert_empty_item(trans, root, path, &key,
                                       sizeof(struct btrfs_inode_item));
-        if (ret == 0 && objectid > root->highest_inode)
-                root->highest_inode = objectid;
         return ret;
 }
 
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;
 }
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 81ba6654c332..9e81f3184f24 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3624,9 +3624,6 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
         if (ret != 0)
                 goto fail;
 
-        if (objectid > root->highest_inode)
-                root->highest_inode = objectid;
-
         inode->i_uid = current_fsuid();
 
         if (dir && (dir->i_mode & S_ISGID)) {
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index f4a7b62f9bea..6e674d76186d 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2951,7 +2951,6 @@ int btrfs_recover_log_trees(struct btrfs_root *log_root_tree)
         struct btrfs_key tmp_key;
         struct btrfs_root *log;
         struct btrfs_fs_info *fs_info = log_root_tree->fs_info;
-        u64 highest_inode;
         struct walk_control wc = {
                 .process_func = process_one_buffer,
                 .stage = 0,
@@ -3010,11 +3009,6 @@ again:
                                                       path);
                         BUG_ON(ret);
                 }
-                ret = btrfs_find_highest_inode(wc.replay_dest, &highest_inode);
-                if (ret == 0) {
-                        wc.replay_dest->highest_inode = highest_inode;
-                        wc.replay_dest->last_inode_alloc = highest_inode;
-                }
 
                 key.offset = found_key.offset - 1;
                 wc.replay_dest->log_root = NULL;