Thanks, Jeff. Acked-by: J. Bruce Fields <[email protected]>
--b. On Fri, Jun 20, 2014 at 02:56:52PM -0400, Jeff Layton wrote: > From: Jeff Layton <[email protected]> > > This is commit a0ef5e19684f0447da9ff0654a12019c484f57ca in mainline. > > While the commit message below doesn't lay this out, we've subsequently > found that there are some cases where an entry that's still in use can > be freed prematurely if a particular operation takes a *very* long time > (on the order of minutes) and/or the server is very busy and doesn't > have a lot of memory dedicated to the DRC. This patch eliminates that > possibility, so it's actually more than just a cleanup. > > The regression crept in in v3.9, and this patch went into mainline in > v3.14. Please apply this to any stable kernel between those two > mainline releases. > > Original patch description follows: > > -------------------------------[snip]---------------------------- > > Currently when we are processing a request, we try to scrape an expired > or over-limit entry off the list in preference to allocating a new one > from the slab. > > This is unnecessarily complicated. Just use the slab layer. > > Signed-off-by: Jeff Layton <[email protected]> > Signed-off-by: J. Bruce Fields <[email protected]> > --- > fs/nfsd/nfscache.c | 36 ++++-------------------------------- > 1 file changed, 4 insertions(+), 32 deletions(-) > > diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c > index ec8d97ddc635..02e8e9ad5750 100644 > --- a/fs/nfsd/nfscache.c > +++ b/fs/nfsd/nfscache.c > @@ -129,13 +129,6 @@ nfsd_reply_cache_alloc(void) > } > > static void > -nfsd_reply_cache_unhash(struct svc_cacherep *rp) > -{ > - hlist_del_init(&rp->c_hash); > - list_del_init(&rp->c_lru); > -} > - > -static void > nfsd_reply_cache_free_locked(struct svc_cacherep *rp) > { > if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) { > @@ -402,22 +395,8 @@ 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) { > - nfsd_reply_cache_unhash(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)) { > @@ -425,7 +404,9 @@ nfsd_cache_lookup(struct svc_rqst *rqstp) > drc_mem_usage += sizeof(*rp); > } > > -search_cache: > + /* go ahead and prune the cache */ > + prune_cache_entries(); > + > found = nfsd_cache_search(rqstp, csum); > if (found) { > if (likely(rp)) > @@ -439,15 +420,6 @@ 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; > -- > 1.9.3 > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
