[bug report] btrfs: turn fs_roots_radix in btrfs_fs_info into an XArray

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Gabriel Niebler,

The patch 06a79e50ff00: "btrfs: turn fs_roots_radix in btrfs_fs_info
into an XArray" from May 3, 2022, leads to the following Smatch
static checker warning:

	fs/btrfs/disk-io.c:4560 btrfs_cleanup_fs_roots()
	warn: ignoring unreachable code.

fs/btrfs/disk-io.c
    4520 int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info)
    4521 {
    4522         struct btrfs_root *roots[8];
    4523         unsigned long index = 0;
    4524         int i;
    4525         int err = 0;
    4526         int grabbed;
    4527 
    4528         while (1) {
    4529                 struct btrfs_root *root;
    4530 
    4531                 spin_lock(&fs_info->fs_roots_lock);
    4532                 if (!xa_find(&fs_info->fs_roots, &index, ULONG_MAX, XA_PRESENT)) {
    4533                         spin_unlock(&fs_info->fs_roots_lock);
    4534                         return err;
    4535                 }
    4536 
    4537                 grabbed = 0;
    4538                 xa_for_each_start(&fs_info->fs_roots, index, root, index) {
    4539                         /* Avoid grabbing roots in dead_roots */
    4540                         if (btrfs_root_refs(&root->root_item) > 0)
    4541                                 roots[grabbed++] = btrfs_grab_root(root);
    4542                         if (grabbed >= ARRAY_SIZE(roots))
    4543                                 break;
    4544                 }
    4545                 spin_unlock(&fs_info->fs_roots_lock);
    4546 
    4547                 for (i = 0; i < grabbed; i++) {
    4548                         if (!roots[i])
    4549                                 continue;
    4550                         index = roots[i]->root_key.objectid;
    4551                         err = btrfs_orphan_cleanup(roots[i]);
    4552                         if (err)
    4553                                 break;
    4554                         btrfs_put_root(roots[i]);
    4555                 }
    4556                 index++;
    4557         }
    4558 
    4559         /* Release the roots that remain uncleaned due to error */
--> 4560         for (; i < grabbed; i++) {

This code is unreachable now.

    4561                 if (roots[i])
    4562                         btrfs_put_root(roots[i]);
    4563         }
    4564         return err;
    4565 }

regards,
dan carpenter