From patchwork Wed Oct 5 14:55:48 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 12999301 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C230AC433F5 for ; Wed, 5 Oct 2022 14:55:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230118AbiJEOz4 (ORCPT ); Wed, 5 Oct 2022 10:55:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47448 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230002AbiJEOzy (ORCPT ); Wed, 5 Oct 2022 10:55:54 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F5C85722C for ; Wed, 5 Oct 2022 07:55:53 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 10D39B81DED for ; Wed, 5 Oct 2022 14:55:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A973DC433C1 for ; Wed, 5 Oct 2022 14:55:49 +0000 (UTC) Subject: [PATCH RFC 2/9] nfsd: rework hashtable handling in nfsd_do_file_acquire From: Chuck Lever To: linux-nfs@vger.kernel.org Date: Wed, 05 Oct 2022 10:55:48 -0400 Message-ID: <166498174879.1527.18235050678404528153.stgit@manet.1015granger.net> In-Reply-To: <166497916751.1527.11190362197003358927.stgit@manet.1015granger.net> References: <166497916751.1527.11190362197003358927.stgit@manet.1015granger.net> User-Agent: StGit/1.5.dev2+g9ce680a5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Jeff Layton nfsd_file is RCU-freed, so we need to hold the rcu_read_lock long enough to get a reference after finding it in the hash. Take the rcu_read_lock() and call rhashtable_lookup directly. Switch to using rhashtable_lookup_insert_key as well, and use the usual retry mechanism if we hit an -EEXIST. Rename the "retry" bool to open_retry, and eliminiate the insert_err goto target. Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever --- fs/nfsd/filecache.c | 52 ++++++++++++++++++++++----------------------------- 1 file changed, 22 insertions(+), 30 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 844c41832d50..a2adfc247648 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -1042,9 +1042,10 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, .need = may_flags & NFSD_FILE_MAY_MASK, .net = SVC_NET(rqstp), }; - struct nfsd_file *nf, *new; - bool retry = true; + bool open_retry = true; + struct nfsd_file *nf; __be32 status; + int ret; status = fh_verify(rqstp, fhp, S_IFREG, may_flags|NFSD_MAY_OWNER_OVERRIDE); @@ -1054,35 +1055,33 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, key.cred = get_current_cred(); retry: - /* Avoid allocation if the item is already in cache */ - nf = rhashtable_lookup_fast(&nfsd_file_rhash_tbl, &key, - nfsd_file_rhash_params); + rcu_read_lock(); + nf = rhashtable_lookup(&nfsd_file_rhash_tbl, &key, + nfsd_file_rhash_params); if (nf) nf = nfsd_file_get(nf); + rcu_read_unlock(); if (nf) goto wait_for_construction; - new = nfsd_file_alloc(&key, may_flags); - if (!new) { + nf = nfsd_file_alloc(&key, may_flags); + if (!nf) { status = nfserr_jukebox; goto out_status; } - nf = rhashtable_lookup_get_insert_key(&nfsd_file_rhash_tbl, - &key, &new->nf_rhash, - nfsd_file_rhash_params); - if (!nf) { - nf = new; - goto open_file; - } - if (IS_ERR(nf)) - goto insert_err; - nf = nfsd_file_get(nf); - if (nf == NULL) { - nf = new; + ret = rhashtable_lookup_insert_key(&nfsd_file_rhash_tbl, + &key, &nf->nf_rhash, + nfsd_file_rhash_params); + if (likely(ret == 0)) goto open_file; - } - nfsd_file_slab_free(&new->nf_rcu); + + nfsd_file_slab_free(&nf->nf_rcu); + if (ret == -EEXIST) + goto retry; + trace_nfsd_file_insert_err(rqstp, key.inode, may_flags, ret); + status = nfserr_jukebox; + goto out_status; wait_for_construction: wait_on_bit(&nf->nf_flags, NFSD_FILE_PENDING, TASK_UNINTERRUPTIBLE); @@ -1090,11 +1089,11 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, /* Did construction of this file fail? */ if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) { trace_nfsd_file_cons_err(rqstp, key.inode, may_flags, nf); - if (!retry) { + if (!open_retry) { status = nfserr_jukebox; goto out; } - retry = false; + open_retry = false; nfsd_file_put_noref(nf); goto retry; } @@ -1142,13 +1141,6 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, smp_mb__after_atomic(); wake_up_bit(&nf->nf_flags, NFSD_FILE_PENDING); goto out; - -insert_err: - nfsd_file_slab_free(&new->nf_rcu); - trace_nfsd_file_insert_err(rqstp, key.inode, may_flags, PTR_ERR(nf)); - nf = NULL; - status = nfserr_jukebox; - goto out_status; } /**