nfsd: Do not refuse to serve out of cache

Currently the knfsd replay cache appears to try to refuse replying to
retries that come within 200ms of the cache entry being created. That
makes limited sense in today's world of high speed TCP.

After a TCP disconnection, a client can very easily reconnect and retry
an rpc in less than 200ms.  If this logic drops that retry, however, the
client may be quite slow to retry again.  This logic is original to the
first reply cache implementation in 2.1, and may have made more sense
for UDP clients that retried much more frequently.

After this patch we will still drop on finding the original request
still in progress.  We may want to fix that as well at some point,
though it's less likely.

Note that svc_check_conn_limits is often the cause of those
disconnections.  We may want to fix that some day.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
index 046b3f04875745019abc3247b2e7e479d96d9dd8..b7559c6f2b9767609f0832f0fb5e0fb80d51fce0 100644 (file)
--- a/fs/nfsd/cache.h
+++ b/fs/nfsd/cache.h
@@ -67,11 +67,6 @@ enum {
        RC_REPLBUFF,
 };
 
-/*
- * If requests are retransmitted within this interval, they're dropped.
- */
-#define RC_DELAY               (HZ/5)
-
 /* Cache entries expire after this time period */
 #define RC_EXPIRE              (120 * HZ)
 

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 334f2ad6070491d2302e93fd7fc87b6603c325f7..637f87c39183e9f1cc0608f515ccda2d6b35274b 100644 (file)
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -394,7 +394,6 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
        __wsum                  csum;
        u32 hash = nfsd_cache_hash(xid);
        struct nfsd_drc_bucket *b = &drc_hashtbl[hash];
-       unsigned long           age;
        int type = rqstp->rq_cachetype;
        int rtn = RC_DOIT;
 
@@ -461,12 +460,11 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
 found_entry:
        nfsdstats.rchits++;
        /* We found a matching entry which is either in progress or done. */
-       age = jiffies - rp->c_timestamp;
        lru_put_end(b, rp);
 
        rtn = RC_DROPIT;
-       /* Request being processed or excessive rexmits */
-       if (rp->c_state == RC_INPROG || age < RC_DELAY)
+       /* Request being processed */
+       if (rp->c_state == RC_INPROG)
                goto out;
 
        /* From the hall of fame of impractical attacks: