On Tue, May 3, 2016 at 1:01 AM, Liu Bo <bo.li.liu@xxxxxxxxxx> wrote:
> Mounting a btrfs can resume previous balance operations asynchronously.
> An user got a crash when one drive has some corrupt sectors.
>
> Since balance can cancel itself in case of any error, we can gracefully
> return errors to upper layers and let balance do the cancel job.
>
> Reported-by: sash <master.b.at.raven@xxxxxxxxxxx>
> Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index bd0f45f..5aed2e2 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -3418,13 +3418,25 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
> ret = btrfs_shrink_device(device, old_size - size_to_free);
> if (ret == -ENOSPC)
> break;
> - BUG_ON(ret);
> + if (ret) {
> + /* btrfs_shrink_device never returns ret > 0 */
> + WARN_ON_ONCE(ret > 0);
> + goto error;
> + }
>
> trans = btrfs_start_transaction(dev_root, 0);
> - BUG_ON(IS_ERR(trans));
> + if (IS_ERR(trans)) {
> + ret = PTR_ERR(trans);
> + goto error;
> + }
>
> ret = btrfs_grow_device(trans, device, old_size);
> - BUG_ON(ret);
> + if (ret) {
> + btrfs_end_transaction(trans, dev_root);
> + /* btrfs_grow_device never returns ret > 0 */
> + WARN_ON_ONCE(ret > 0);
> + goto error;
> + }
>
> btrfs_end_transaction(trans, dev_root);
> }
Just a heads up that this seems to introduce a valid warning, since it now
can goto error before the first initializing use of path:
fs/btrfs/volumes.c: In function 'btrfs_balance':
fs/btrfs/volumes.c:3601:2: warning: 'path' may be used uninitialized
in this function [-Wmaybe-uninitialized]
btrfs_free_path(path);
^
fs/btrfs/volumes.c:3385:21: note: 'path' was declared here
struct btrfs_path *path;
^
(it's really in __btrfs_balance which got inlined, so gcc thinks it's
at the call site).
Simply setting path = NULL at the beginning of __btrfs_balance fixes it, since
btrfs_free_path allows NULL values.
cheers
Holger
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