NFSv4: Avoid thundering herd issues with nfs_release_seqid
Store a pointer to the rpc_task in struct nfs_seqid so that we can wake up
only that request that is able to grab the lock after we've released it.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index f0e9881..7d09860 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -916,20 +916,28 @@
if (new != NULL) {
new->sequence = counter;
INIT_LIST_HEAD(&new->list);
+ new->task = NULL;
}
return new;
}
void nfs_release_seqid(struct nfs_seqid *seqid)
{
- if (!list_empty(&seqid->list)) {
- struct nfs_seqid_counter *sequence = seqid->sequence;
+ struct nfs_seqid_counter *sequence;
- spin_lock(&sequence->lock);
- list_del_init(&seqid->list);
- spin_unlock(&sequence->lock);
- rpc_wake_up(&sequence->wait);
+ if (list_empty(&seqid->list))
+ return;
+ sequence = seqid->sequence;
+ spin_lock(&sequence->lock);
+ list_del_init(&seqid->list);
+ if (!list_empty(&sequence->list)) {
+ struct nfs_seqid *next;
+
+ next = list_first_entry(&sequence->list,
+ struct nfs_seqid, list);
+ rpc_wake_up_queued_task(&sequence->wait, next->task);
}
+ spin_unlock(&sequence->lock);
}
void nfs_free_seqid(struct nfs_seqid *seqid)
@@ -1000,6 +1008,7 @@
int status = 0;
spin_lock(&sequence->lock);
+ seqid->task = task;
if (list_empty(&seqid->list))
list_add_tail(&seqid->list, &sequence->list);
if (list_first_entry(&sequence->list, struct nfs_seqid, list) == seqid)