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sunrpc/cache: drop reference when sunrpc_cache_pipe_upcall() detects a race 

sunrpc_cache_pipe_upcall() can detect a race if CACHE_PENDING is no longer
set.  In this case it aborts the queuing of the upcall.
However it has already taken a new counted reference on "h" and
doesn't "put" it, even though it frees the data structure holding the reference.

So let's delay the "cache_get" until we know we need it.

Fixes: f9e1aedc6c ("sunrpc/cache: remove races with queuing an upcall.")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
NeilBrown 2016-03-04 17:20:13 +11:00 committed by J. Bruce Fields
parent 956ccef3c9
commit a6ab1e8126
1 changed files with 3 additions and 3 deletions
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6
net/sunrpc/cache.c
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@ -1182,14 +1182,14 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
}
crq->q.reader = 0;
crq->item = cache_get(h);
crq->buf = buf;
crq->len = 0;
crq->readers = 0;
spin_lock(&queue_lock);
if (test_bit(CACHE_PENDING, &h->flags))
if (test_bit(CACHE_PENDING, &h->flags)) {
crq->item = cache_get(h);
list_add_tail(&crq->q.list, &detail->queue);
else
} else
/* Lost a race, no longer PENDING, so don't enqueue */
ret = -EAGAIN;
spin_unlock(&queue_lock);