From f16b6e8d838b2e2bb4561201311c66ac02ad67df Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 12 Aug 2010 17:04:06 +1000 Subject: 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 Signed-off-by: J. Bruce Fields --- include/linux/sunrpc/cache.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/sunrpc/cache.h') diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h index ece432b7f87f..52a7d7224e90 100644 --- a/include/linux/sunrpc/cache.h +++ b/include/linux/sunrpc/cache.h @@ -125,6 +125,9 @@ 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 -- cgit v1.2.1