+++ /dev/null
-Patch-mainline: submitted 04aug2009
-References: bnc#498708
-From: NeilBrown <neilb@suse.de>
-Date: Tue, 4 Aug 2009 15:06:38 +1000
-Subject: [PATCH 07/12] sunrpc/cache: allow thread 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/ We NFSv4, requests can be quite complex and re-trying a whole
- request when a later part fails should only be a list-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.
-
-Signed-off-by: NeilBrown <neilb@suse.de>
-
----
- include/linux/sunrpc/cache.h | 3 ++
- net/sunrpc/cache.c | 44 ++++++++++++++++++++++++++++++++++++++++++-
- net/sunrpc/svc_xprt.c | 11 ++++++++++
- 3 files changed, 57 insertions(+), 1 deletion(-)
-
---- linux-2.6.27-SLE11_BRANCH.orig/include/linux/sunrpc/cache.h
-+++ linux-2.6.27-SLE11_BRANCH/include/linux/sunrpc/cache.h
-@@ -112,6 +112,9 @@ struct cache_detail {
- */
- struct cache_req {
- struct cache_deferred_req *(*defer)(struct cache_req *req);
-+ int thread_wait; /* How long (jiffies) we can block the
-+ * current thread to wait for updates.
-+ */
- };
- /* this must be embedded in a deferred_request that is being
- * delayed awaiting cache-fill
---- linux-2.6.27-SLE11_BRANCH.orig/net/sunrpc/cache.c
-+++ linux-2.6.27-SLE11_BRANCH/net/sunrpc/cache.c
-@@ -560,10 +560,22 @@ static LIST_HEAD(cache_defer_list);
- static struct list_head cache_defer_hash[DFR_HASHSIZE];
- static int cache_defer_cnt;
-
-+struct thread_deferred_req {
-+ struct cache_deferred_req handle;
-+ wait_queue_head_t wait;
-+};
-+static void cache_restart_thread(struct cache_deferred_req *dreq, int too_many)
-+{
-+ struct thread_deferred_req *dr =
-+ container_of(dreq, struct thread_deferred_req, handle);
-+ wake_up(&dr->wait);
-+}
-+
- static int cache_defer_req(struct cache_req *req, struct cache_head *item)
- {
- struct cache_deferred_req *dreq, *discard;
- int hash = DFR_HASH(item);
-+ struct thread_deferred_req sleeper;
-
- if (cache_defer_cnt >= DFR_MAX) {
- /* too much in the cache, randomly drop this one,
-@@ -572,7 +584,14 @@ static int cache_defer_req(struct cache_
- if (net_random()&1)
- return 0;
- }
-- dreq = req->defer(req);
-+ if (req->thread_wait) {
-+ dreq = &sleeper.handle;
-+ init_waitqueue_head(&sleeper.wait);
-+ dreq->revisit = cache_restart_thread;
-+ } else
-+ dreq = req->defer(req);
-+
-+ retry:
- if (dreq == NULL)
- return 0;
-
-@@ -606,6 +625,29 @@ static int cache_defer_req(struct cache_
- cache_revisit_request(item);
- return 0;
- }
-+
-+ if (dreq == &sleeper.handle) {
-+ wait_event_interruptible_timeout(
-+ sleeper.wait,
-+ !test_bit(CACHE_PENDING, &item->flags)
-+ || list_empty(&sleeper.handle.hash),
-+ req->thread_wait);
-+ spin_lock(&cache_defer_lock);
-+ if (!list_empty(&sleeper.handle.hash)) {
-+ list_del_init(&sleeper.handle.recent);
-+ list_del_init(&sleeper.handle.hash);
-+ cache_defer_cnt--;
-+ }
-+ spin_unlock(&cache_defer_lock);
-+ if (test_bit(CACHE_PENDING, &item->flags)) {
-+ /* item is still pending, try request
-+ * deferral
-+ */
-+ dreq = req->defer(req);
-+ goto retry;
-+ }
-+ return 0;
-+ }
- return 1;
- }
-
---- linux-2.6.27-SLE11_BRANCH.orig/net/sunrpc/svc_xprt.c
-+++ linux-2.6.27-SLE11_BRANCH/net/sunrpc/svc_xprt.c
-@@ -593,12 +593,23 @@ int svc_recv(struct svc_rqst *rqstp, lon
- return -EINTR;
-
- spin_lock_bh(&pool->sp_lock);
-+
-+ /* Normally we will wait up to 5 seconds for any required
-+ * cache information to be provided.
-+ */
-+ rqstp->rq_chandle.thread_wait = 5*HZ;
- xprt = svc_xprt_dequeue(pool);
- if (xprt) {
- rqstp->rq_xprt = xprt;
- 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);
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