Messages in this thread | | | Date | Fri, 26 Apr 2024 21:09:41 +0100 | From | Al Viro <> | Subject | Re: [RFC v2 1/1] fs/namespace: defer RCU sync for MNT_DETACH umount |
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On Fri, Apr 26, 2024 at 03:53:48PM -0400, Lucas Karpinski wrote:
> -static void namespace_unlock(void) > +static void free_mounts(struct hlist_head *mount_list) > { > - struct hlist_head head; > struct hlist_node *p; > struct mount *m; > + > + hlist_for_each_entry_safe(m, p, mount_list, mnt_umount) { > + hlist_del(&m->mnt_umount); > + mntput(&m->mnt);
.. which may block in quite a few ways.
> + } > +} > + > +static void delayed_mount_release(struct rcu_head *head) > +{ > + struct mount_delayed_release *drelease = > + container_of(head, struct mount_delayed_release, rcu); > + > + free_mounts(&drelease->release_list);
.. and therefore so can this.
> + kfree(drelease); > +}
> + call_rcu(&drelease->rcu, delayed_mount_release);
.. which is a bad idea, since call_rcu() callbacks are run from interrupt context. Which makes blocking in them a problem.
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