btrfs: use on-stack variable for block reserve in btrfs_replace_file_extents()

We can avoid potential memory allocation failure in
btrfs_replace_file_extents() as the block reserve lifetime is limited to
the scope of the function. This requires +48 bytes on stack.

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

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 8ce6f45f45e0bbfb1fb743ec90dd81e678d792d7..2902de88dd1b2891068d7641dcbb0537c5ecf171 100644 (file)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2341,7 +2341,7 @@ int btrfs_replace_file_extents(struct btrfs_inode *inode,
        u64 min_size = btrfs_calc_insert_metadata_size(fs_info, 1);
        u64 ino_size = round_up(inode->vfs_inode.i_size, fs_info->sectorsize);
        struct btrfs_trans_handle *trans = NULL;
-       struct btrfs_block_rsv *rsv;
+       struct btrfs_block_rsv rsv;
        unsigned int rsv_count;
        u64 cur_offset;
        u64 len = end - start;
@@ -2350,13 +2350,9 @@ int btrfs_replace_file_extents(struct btrfs_inode *inode,
        if (end <= start)
                return -EINVAL;
 
-       rsv = btrfs_alloc_block_rsv(fs_info, BTRFS_BLOCK_RSV_TEMP);
-       if (!rsv) {
-               ret = -ENOMEM;
-               goto out;
-       }
-       rsv->size = btrfs_calc_insert_metadata_size(fs_info, 1);
-       rsv->failfast = true;
+       btrfs_init_metadata_block_rsv(fs_info, &rsv, BTRFS_BLOCK_RSV_TEMP);
+       rsv.size = btrfs_calc_insert_metadata_size(fs_info, 1);
+       rsv.failfast = true;
 
        /*
         * 1 - update the inode
@@ -2373,14 +2369,14 @@ int btrfs_replace_file_extents(struct btrfs_inode *inode,
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                trans = NULL;
-               goto out_free;
+               goto out_release;
        }
 
-       ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, rsv,
+       ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, &rsv,
                                      min_size, false);
        if (WARN_ON(ret))
                goto out_trans;
-       trans->block_rsv = rsv;
+       trans->block_rsv = &rsv;
 
        cur_offset = start;
        drop_args.path = path;
@@ -2496,10 +2492,10 @@ int btrfs_replace_file_extents(struct btrfs_inode *inode,
                }
 
                ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv,
-                                             rsv, min_size, false);
+                                             &rsv, min_size, false);
                if (WARN_ON(ret))
                        break;
-               trans->block_rsv = rsv;
+               trans->block_rsv = &rsv;
 
                cur_offset = drop_args.drop_end;
                len = end - cur_offset;
@@ -2576,16 +2572,15 @@ int btrfs_replace_file_extents(struct btrfs_inode *inode,
 
 out_trans:
        if (!trans)
-               goto out_free;
+               goto out_release;
 
        trans->block_rsv = &fs_info->trans_block_rsv;
        if (ret)
                btrfs_end_transaction(trans);
        else
                *trans_out = trans;
-out_free:
-       btrfs_free_block_rsv(fs_info, rsv);
-out:
+out_release:
+       btrfs_block_rsv_release(fs_info, &rsv, (u64)-1, NULL);
        return ret;
 }