> + if (nmaps == 0) {
> + /*
> + * Unexpected ENOSPC - the transaction reservation should have
> + * guaranteed that this allocation will succeed. We don't know
> + * why this happened, so just back out gracefully.
> + *
> + * We commit the transaction instead of cancelling it as it may
> + * be dirty due to extent count upgrade. This avoids a potential
> + * filesystem shutdown when this happens. We ignore any error
> + * from the transaction commit - we always return -ENOSPC to the
> + * caller here so we really don't care if the commit fails for
> + * some unknown reason...
> + */
> + xfs_trans_commit(tp);
> + return -ENOSPC;
A cancel and thus shutdown does seem like the right behavior for a trap
for an unknown bug..
