> Yeah, I've noticed the same hang, but hadn't able to determine why it
> was hanging. I suspect that that hang is what's tickles the bug that my
> patch fixes. With the hang, we see the client doing retransmits and not
> getting replies and that means that we exercise the DRC more...
FYI here is the one that just kills the silly direct reclaim. It also
fixes the oops, but I still see the hang:
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 9186c7c..dd260a1 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -380,11 +380,8 @@ nfsd_cache_search(struct svc_rqst *rqstp, __wsum csum)
}
/*
- * Try to find an entry matching the current call in the cache. When none
- * is found, we try to grab the oldest expired entry off the LRU list. If
- * a suitable one isn't there, then drop the cache_lock and allocate a
- * new one, then search again in case one got inserted while this thread
- * didn't hold the lock.
+ * Try to find an entry matching the current call in the cache and if none is
+ * found allocate and insert a new one.
*/
int
nfsd_cache_lookup(struct svc_rqst *rqstp)
@@ -409,22 +406,8 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
/*
* Since the common case is a cache miss followed by an insert,
- * preallocate an entry. First, try to reuse the first entry on the LRU
- * if it works, then go ahead and prune the LRU list.
+ * preallocate an entry.
*/
- spin_lock(&cache_lock);
- if (!list_empty(&lru_head)) {
- rp = list_first_entry(&lru_head, struct svc_cacherep, c_lru);
- if (nfsd_cache_entry_expired(rp) ||
- num_drc_entries >= max_drc_entries) {
- lru_put_end(rp);
- prune_cache_entries();
- goto search_cache;
- }
- }
-
- /* No expired ones available, allocate a new one. */
- spin_unlock(&cache_lock);
rp = nfsd_reply_cache_alloc();
spin_lock(&cache_lock);
if (likely(rp)) {
@@ -432,7 +415,6 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
drc_mem_usage += sizeof(*rp);
}
-search_cache:
found = nfsd_cache_search(rqstp, csum);
if (found) {
if (likely(rp))
@@ -446,15 +428,6 @@ search_cache:
goto out;
}
- /*
- * We're keeping the one we just allocated. Are we now over the
- * limit? Prune one off the tip of the LRU in trade for the one we
- * just allocated if so.
- */
- if (num_drc_entries >= max_drc_entries)
- nfsd_reply_cache_free_locked(list_first_entry(&lru_head,
- struct svc_cacherep, c_lru));
-
nfsdstats.rcmisses++;
rqstp->rq_cacherep = rp;
rp->c_state = RC_INPROG;
--
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