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authorNeilBrown <neilb@suse.de>2010-08-12 11:04:06 +0400
committerJ. Bruce Fields <bfields@redhat.com>2010-09-08 03:22:07 +0400
commitf16b6e8d838b2e2bb4561201311c66ac02ad67df (patch)
tree92c4ab62aa566029ce25989ef7dc8e3634365f63 /include/linux/sunrpc
parentc5b29f885afe890f953f7f23424045cdad31d3e4 (diff)
downloadlinux-f16b6e8d838b2e2bb4561201311c66ac02ad67df.tar.xz
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 'include/linux/sunrpc')
-rw-r--r--include/linux/sunrpc/cache.h3
1 files changed, 3 insertions, 0 deletions
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