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locks: add a new "lm_owner_key" lock operation

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Currently, the hashing that the locking code uses to add these values
to the blocked_hash is simply calculated using fl_owner field. That's
valid in most cases except for server-side lockd, which validates the
owner of a lock based on fl_owner and fl_pid.

In the case where you have a small number of NFS clients doing a lot
of locking between different processes, you could end up with all
the blocked requests sitting in a very small number of hash buckets.

Add a new lm_owner_key operation to the lock_manager_operations that
will generate an unsigned long to use as the key in the hashtable.
That function is only implemented for server-side lockd, and simply
XORs the fl_owner and fl_pid.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Jeff Layton
2013-06-21 08:58:19 -04:00
committed by Al Viro
parent 48f7418654
commit 3999e49364
4 changed files with 34 additions and 7 deletions
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12
fs/lockd/svclock.c
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@@ -744,8 +744,20 @@ static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
}
/*
* Since NLM uses two "keys" for tracking locks, we need to hash them down
* to one for the blocked_hash. Here, we're just xor'ing the host address
* with the pid in order to create a key value for picking a hash bucket.
*/
static unsigned long
nlmsvc_owner_key(struct file_lock *fl)
{
return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid;
}
const struct lock_manager_operations nlmsvc_lock_operations = {
.lm_compare_owner = nlmsvc_same_owner,
.lm_owner_key = nlmsvc_owner_key,
.lm_notify = nlmsvc_notify_blocked,
.lm_grant = nlmsvc_grant_deferred,
};