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nvme: avoid race in shutdown namespace removal 

When we remove the siblings entry, we update ns->head->list, hence we
can't separate the removal and test for being empty. They have to be
in the same critical section to avoid a race.

To avoid breaking the refcounting imbalance again, add a list empty
check to nvme_find_ns_head.

Fixes: 5396fdac56 ("nvme: fix refcounting imbalance when all paths are down")
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Daniel Wagner 2021-09-02 11:20:02 +02:00 committed by Christoph Hellwig
parent 0bd46e22c5
commit 9edceaf430
1 changed files with 7 additions and 8 deletions
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15
drivers/nvme/host/core.c
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@ -3524,7 +3524,9 @@ static struct nvme_ns_head *nvme_find_ns_head(struct nvme_subsystem *subsys,
lockdep_assert_held(&subsys->lock);
list_for_each_entry(h, &subsys->nsheads, entry) {
if (h->ns_id == nsid && nvme_tryget_ns_head(h))
if (h->ns_id != nsid)
continue;
if (!list_empty(&h->list) && nvme_tryget_ns_head(h))
return h;
}
@ -3843,6 +3845,10 @@ static void nvme_ns_remove(struct nvme_ns *ns)
mutex_lock(&ns->ctrl->subsys->lock);
list_del_rcu(&ns->siblings);
if (list_empty(&ns->head->list)) {
list_del_init(&ns->head->entry);
last_path = true;
}
mutex_unlock(&ns->ctrl->subsys->lock);
/* guarantee not available in head->list */
@ -3863,13 +3869,6 @@ static void nvme_ns_remove(struct nvme_ns *ns)
list_del_init(&ns->list);
up_write(&ns->ctrl->namespaces_rwsem);
/* Synchronize with nvme_init_ns_head() */
mutex_lock(&ns->head->subsys->lock);
if (list_empty(&ns->head->list)) {
list_del_init(&ns->head->entry);
last_path = true;
}
mutex_unlock(&ns->head->subsys->lock);
if (last_path)
nvme_mpath_shutdown_disk(ns->head);
nvme_put_ns(ns);