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authorNeilBrown <neilb@suse.de>2010-08-12 17:04:06 +1000
committerJ. Bruce Fields <bfields@redhat.com>2010-09-07 19:22:07 -0400
commitf16b6e8d838b2e2bb4561201311c66ac02ad67df (patch)
tree92c4ab62aa566029ce25989ef7dc8e3634365f63 /net/sunrpc/svc_xprt.c
parentc5b29f885afe890f953f7f23424045cdad31d3e4 (diff)
sunrpc/cache: allow threads to block while waiting for cache update.
The current practice of waiting for cache updates by queueing the whole request to be retried has (at least) two problems. 1/ With NFSv4, requests can be quite complex and re-trying a whole request when a later part fails should only be a last-resort, not a normal practice. 2/ Large requests, and in particular any 'write' request, will not be queued by the current code and doing so would be undesirable. In many cases only a very sort wait is needed before the cache gets valid data. So, providing the underlying transport permits it by setting ->thread_wait, arrange to wait briefly for an upcall to be completed (as reflected in the clearing of CACHE_PENDING). If the short wait was not long enough and CACHE_PENDING is still set, fall back on the old approach. The 'thread_wait' value is set to 5 seconds when there are spare threads, and 1 second when there are no spare threads. These values are probably much higher than needed, but will ensure some forward progress. Note that as we only request an update for a non-valid item, and as non-valid items are updated in place it is extremely unlikely that cache_check will return -ETIMEDOUT. Normally cache_defer_req will sleep for a short while and then find that the item is_valid. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Diffstat (limited to 'net/sunrpc/svc_xprt.c')
-rw-r--r--net/sunrpc/svc_xprt.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index cbc084939dd8..8ff6840866fa 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -651,6 +651,11 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
if (signalled() || kthread_should_stop())
return -EINTR;
+ /* Normally we will wait up to 5 seconds for any required
+ * cache information to be provided.
+ */
+ rqstp->rq_chandle.thread_wait = 5*HZ;
+
spin_lock_bh(&pool->sp_lock);
xprt = svc_xprt_dequeue(pool);
if (xprt) {
@@ -658,6 +663,12 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
svc_xprt_get(xprt);
rqstp->rq_reserved = serv->sv_max_mesg;
atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
+
+ /* As there is a shortage of threads and this request
+ * had to be queue, don't allow the thread to wait so
+ * long for cache updates.
+ */
+ rqstp->rq_chandle.thread_wait = 1*HZ;
} else {
/* No data pending. Go to sleep */
svc_thread_enqueue(pool, rqstp);