Hello Jeff Mahoney,
This is a semi-automatic email about new static checker warnings.
The patch cab45e22da48: "btrfs: add tracing for failed reservations"
from Oct 16, 2013, leads to the following Smatch complaint:
fs/btrfs/extent-tree.c:3710 btrfs_check_data_free_space()
error: we previously assumed 'data_sinfo' could be null (see line 3629)
fs/btrfs/extent-tree.c
3628 data_sinfo = fs_info->data_sinfo;
3629 if (!data_sinfo)
^^^^^^^^^^^
Existing check.
3630 goto alloc;
3631
3632 again:
3633 /* make sure we have enough space to handle the data first */
3634 spin_lock(&data_sinfo->lock);
3635 used = data_sinfo->bytes_used + data_sinfo->bytes_reserved +
3636 data_sinfo->bytes_pinned + data_sinfo->bytes_readonly +
3637 data_sinfo->bytes_may_use;
3638
3639 if (used + bytes > data_sinfo->total_bytes) {
3640 struct btrfs_trans_handle *trans;
3641
3642 /*
3643 * if we don't have enough free bytes in this space
then we need
3644 * to alloc a new chunk.
3645 */
3646 if (!data_sinfo->full && alloc_chunk) {
3647 u64 alloc_target;
3648
3649 data_sinfo->force_alloc = CHUNK_ALLOC_FORCE;
3650 spin_unlock(&data_sinfo->lock);
3651 alloc:
3652 alloc_target = btrfs_get_alloc_profile(root, 1);
3653 /*
3654 * It is ugly that we don't call nolock join
3655 * transaction for the free space inode case
here.
3656 * But it is safe because we only do the data
space
3657 * reservation for the free space cache in the
3658 * transaction context, the common join
transaction
3659 * just increase the counter of the current
transaction
3660 * handler, doesn't try to acquire the
trans_lock of
3661 * the fs.
3662 */
3663 trans = btrfs_join_transaction(root);
3664 if (IS_ERR(trans))
3665 return PTR_ERR(trans);
3666
3667 ret = do_chunk_alloc(trans,
root->fs_info->extent_root,
3668 alloc_target,
3669 CHUNK_ALLOC_NO_FORCE);
3670 btrfs_end_transaction(trans, root);
3671 if (ret < 0) {
3672 if (ret != -ENOSPC)
3673 return ret;
3674 else
3675 goto commit_trans;
^^^^^^^^^^^^^^^^^
Imagine we hit this goto and data_sinfo is NULL.
3676 }
3677
3678 if (!data_sinfo)
3679 data_sinfo = fs_info->data_sinfo;
3680
3681 goto again;
3682 }
3683
3684 /*
3685 * If we don't have enough pinned space to deal with
this
3686 * allocation don't bother committing the transaction.
3687 */
3688 if
(percpu_counter_compare(&data_sinfo->total_bytes_pinned,
3689 bytes) < 0)
3690 committed = 1;
3691 spin_unlock(&data_sinfo->lock);
3692
3693 /* commit the current transaction and try again */
3694 commit_trans:
3695 if (!committed &&
3696 !atomic_read(&root->fs_info->open_ioctl_trans)) {
3697 committed = 1;
3698
3699 trans = btrfs_join_transaction(root);
3700 if (IS_ERR(trans))
3701 return PTR_ERR(trans);
3702 ret = btrfs_commit_transaction(trans, root);
3703 if (ret)
3704 return ret;
3705 goto again;
3706 }
3707
3708 trace_btrfs_space_reservation(root->fs_info,
3709 "space_info:enospc",
3710 data_sinfo->flags, bytes,
1);
^^^^^^^^^^^^^^^^^
Patch introduces an unchecked dereference.
3711 return -ENOSPC;
3712 }
regards,
dan carpenter
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