Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-qa0-f48.google.com ([209.85.216.48]:34531 "EHLO mail-qa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751035AbaJQKVX (ORCPT ); Fri, 17 Oct 2014 06:21:23 -0400 Received: by mail-qa0-f48.google.com with SMTP id dc16so277944qab.7 for ; Fri, 17 Oct 2014 03:21:22 -0700 (PDT) From: Jeff Layton To: bfields@fieldses.org Cc: linux-nfs@vger.kernel.org Subject: [PATCH] nfsd: convert nfs4_file searches to use RCU Date: Fri, 17 Oct 2014 06:21:15 -0400 Message-Id: <1413541275-3884-1-git-send-email-jlayton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: The global state_lock protects the file_hashtbl, and that has the potential to be a scalability bottleneck. Address this by making the file_hashtbl use RCU. Add a rcu_head to the nfs4_file and use that when freeing ones that have been hashed. Convert find_file to use a lockless lookup. Convert find_or_add_file to attempt a lockless lookup first, and then fall back to doing the "normal" locked search and insert if that fails to find anything. Signed-off-by: Jeff Layton --- fs/nfsd/nfs4state.c | 36 +++++++++++++++++++++++++++--------- fs/nfsd/state.h | 1 + 2 files changed, 28 insertions(+), 9 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index e9c3afe4b5d3..9bd3bcfee3c2 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -280,15 +280,22 @@ static void nfsd4_free_file(struct nfs4_file *f) kmem_cache_free(file_slab, f); } +static void nfsd4_free_file_rcu(struct rcu_head *rcu) +{ + struct nfs4_file *fp = container_of(rcu, struct nfs4_file, fi_rcu); + + nfsd4_free_file(fp); +} + static inline void put_nfs4_file(struct nfs4_file *fi) { might_lock(&state_lock); if (atomic_dec_and_lock(&fi->fi_ref, &state_lock)) { - hlist_del(&fi->fi_hash); + hlist_del_rcu(&fi->fi_hash); spin_unlock(&state_lock); - nfsd4_free_file(fi); + call_rcu(&fi->fi_rcu, nfsd4_free_file_rcu); } } @@ -3073,7 +3080,7 @@ static void nfsd4_init_file(struct nfs4_file *fp, struct knfsd_fh *fh) fp->fi_share_deny = 0; memset(fp->fi_fds, 0, sizeof(fp->fi_fds)); memset(fp->fi_access, 0, sizeof(fp->fi_access)); - hlist_add_head(&fp->fi_hash, &file_hashtbl[hashval]); + hlist_add_head_rcu(&fp->fi_hash, &file_hashtbl[hashval]); } void @@ -3313,12 +3320,19 @@ find_file_locked(struct knfsd_fh *fh) static struct nfs4_file * find_file(struct knfsd_fh *fh) { - struct nfs4_file *fp; + struct nfs4_file *fp, *ret = NULL; + unsigned int hashval = file_hashval(fh); - spin_lock(&state_lock); - fp = find_file_locked(fh); - spin_unlock(&state_lock); - return fp; + rcu_read_lock(); + hlist_for_each_entry_rcu(fp, &file_hashtbl[hashval], fi_hash) { + if (nfsd_fh_match(&fp->fi_fhandle, fh)) { + if (atomic_inc_not_zero(&fp->fi_ref)) + ret = fp; + break; + } + } + rcu_read_unlock(); + return ret; } static struct nfs4_file * @@ -3326,9 +3340,13 @@ find_or_add_file(struct nfs4_file *new, struct knfsd_fh *fh) { struct nfs4_file *fp; + fp = find_file(fh); + if (fp) + return fp; + spin_lock(&state_lock); fp = find_file_locked(fh); - if (fp == NULL) { + if (likely(fp == NULL)) { nfsd4_init_file(new, fh); fp = new; } diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index 8e85e07efce6..530470a35ecd 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -490,6 +490,7 @@ struct nfs4_file { atomic_t fi_access[2]; u32 fi_share_deny; struct file *fi_deleg_file; + struct rcu_head fi_rcu; atomic_t fi_delegees; struct knfsd_fh fi_fhandle; bool fi_had_conflict; -- 1.9.3