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NLM: don't requeue block if it was invalidated while GRANT_MSG was in flight

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It's possible for lockd to catch a SIGKILL while a GRANT_MSG callback
is in flight. If this happens we don't want lockd to insert the block
back into the nlm_blocked list.

This helps that situation, but there's still a possible race. Fixing
that will mean adding real locking for nlm_blocked.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
This commit is contained in:
Jeff Layton 2008-02-06 11:34:13 -05:00 committed by J. Bruce Fields
parent 9706501e43
commit c64e80d55d
1 changed files with 11 additions and 0 deletions
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11
fs/lockd/svclock.c
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@ -795,6 +795,17 @@ static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
dprintk("lockd: GRANT_MSG RPC callback\n");
/* if the block is not on a list at this point then it has
* been invalidated. Don't try to requeue it.
*
* FIXME: it's possible that the block is removed from the list
* after this check but before the nlmsvc_insert_block. In that
* case it will be added back. Perhaps we need better locking
* for nlm_blocked?
*/
if (list_empty(&block->b_list))
return;
/* Technically, we should down the file semaphore here. Since we
* move the block towards the head of the queue only, no harm
* can be done, though. */