From patchwork Fri Oct 28 18:57:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 13024224 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 F41DDC38A02 for ; Fri, 28 Oct 2022 18:57:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229455AbiJ1S5T (ORCPT ); Fri, 28 Oct 2022 14:57:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229935AbiJ1S5S (ORCPT ); Fri, 28 Oct 2022 14:57:18 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 036971ABA3B for ; Fri, 28 Oct 2022 11:57:18 -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 AA2F1B82C8D for ; Fri, 28 Oct 2022 18:57:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2683C433D7; Fri, 28 Oct 2022 18:57:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666983435; bh=19GN2WutVnfU1eKRekedqCHUhQm55dxuykeR22OypyA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q7ZHwZ6vvqlN4G1gKYgYg30XUSdqdy/+WKE7bP2yBOEVDdZECUhubFZpPlkUzYod+ dJThnW6amsBmLxOLDxhofqSti2lFIi9pbx2A8lDDcLw6uPOHCsvKpnW8tGEZBPb/xY ptQyxb8tTMuJUqQqBItMcsDSD5TrUmvMhwruVU/1LJgRWYiZZsJ9r4acJy183QssWX qNININq0Lad4fipuoM/1PJoejfRGB8V/HFL1e2MjqCDcZR7rPBKAXDnHPuiIxriDMs ixEF73CEy1kNCNmvhmYTswByx5hYbptKwWvWG9ZxMCMlQEDfEb2fpZuzZZu2/oD07R xF9sk6Lk1eGAA== From: Jeff Layton To: chuck.lever@oracle.com Cc: linux-nfs@vger.kernel.org, neilb@suse.de Subject: [PATCH v3 1/4] nfsd: remove the pages_flushed statistic from filecache Date: Fri, 28 Oct 2022 14:57:09 -0400 Message-Id: <20221028185712.79863-2-jlayton@kernel.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221028185712.79863-1-jlayton@kernel.org> References: <20221028185712.79863-1-jlayton@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org We're counting mapping->nrpages, but not all of those are necessarily dirty. We don't really have a simple way to count just the dirty pages, so just remove this stat since it's not accurate. Signed-off-by: Jeff Layton --- fs/nfsd/filecache.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 98c6b5f51bc8..f8ebbf7daa18 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -32,7 +32,6 @@ static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits); static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions); static DEFINE_PER_CPU(unsigned long, nfsd_file_releases); static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age); -static DEFINE_PER_CPU(unsigned long, nfsd_file_pages_flushed); static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions); struct nfsd_fcache_disposal { @@ -370,7 +369,6 @@ nfsd_file_flush(struct nfsd_file *nf) if (!file || !(file->f_mode & FMODE_WRITE)) return; - this_cpu_add(nfsd_file_pages_flushed, file->f_mapping->nrpages); if (vfs_fsync(file, 1) != 0) nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id)); } @@ -998,7 +996,6 @@ nfsd_file_cache_shutdown(void) per_cpu(nfsd_file_acquisitions, i) = 0; per_cpu(nfsd_file_releases, i) = 0; per_cpu(nfsd_file_total_age, i) = 0; - per_cpu(nfsd_file_pages_flushed, i) = 0; per_cpu(nfsd_file_evictions, i) = 0; } } @@ -1212,7 +1209,7 @@ nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp, */ int nfsd_file_cache_stats_show(struct seq_file *m, void *v) { - unsigned long releases = 0, pages_flushed = 0, evictions = 0; + unsigned long releases = 0, evictions = 0; unsigned long hits = 0, acquisitions = 0; unsigned int i, count = 0, buckets = 0; unsigned long lru = 0, total_age = 0; @@ -1240,7 +1237,6 @@ int nfsd_file_cache_stats_show(struct seq_file *m, void *v) releases += per_cpu(nfsd_file_releases, i); total_age += per_cpu(nfsd_file_total_age, i); evictions += per_cpu(nfsd_file_evictions, i); - pages_flushed += per_cpu(nfsd_file_pages_flushed, i); } seq_printf(m, "total entries: %u\n", count); @@ -1254,6 +1250,5 @@ int nfsd_file_cache_stats_show(struct seq_file *m, void *v) seq_printf(m, "mean age (ms): %ld\n", total_age / releases); else seq_printf(m, "mean age (ms): -\n"); - seq_printf(m, "pages flushed: %lu\n", pages_flushed); return 0; } From patchwork Fri Oct 28 18:57:10 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 13024226 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 64042FA3746 for ; Fri, 28 Oct 2022 18:57:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230111AbiJ1S5V (ORCPT ); Fri, 28 Oct 2022 14:57:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229935AbiJ1S5U (ORCPT ); Fri, 28 Oct 2022 14:57:20 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5C6A1D2B54 for ; Fri, 28 Oct 2022 11:57:18 -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 44DF0B82C8F for ; Fri, 28 Oct 2022 18:57:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97C37C433B5; Fri, 28 Oct 2022 18:57:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666983436; bh=qOT8H5RpLfKLLrfR6El2eT1QdYz3jtsg++rTNoL3JDw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=f3RQG6O1CqVlD4Khjr8x9CBCBWfffwtd+e5A/vWK7f1PC4tHoxFY7rroo4bAEcdJW VU3FMiOmhxYY7Gmg8oFLTnqqAkjpVwvW5EuL21gUUYC4T+NMAVogKN/PGxcjnyiC46 HdxUIerxshJM829n4JN36BUmzcRC95tc9ZveXboeYFBsQve0eb8p1vEUZ+vFwhfpwA 6slJOL1aHR/4VO7u+SzfdkIvCXV99KTVNIJLz2+pfoYyXud9Cg9l7Adya7mHQOb6I+ bXM/Y0b6XA8sTz03jHq3C1n2eMvCsooIQU3pgaBgwq7TQM4JKEDYgMqOV/12UjpAeD tlL6t+CmdGuSQ== From: Jeff Layton To: chuck.lever@oracle.com Cc: linux-nfs@vger.kernel.org, neilb@suse.de Subject: [PATCH v3 2/4] nfsd: rework refcounting in filecache Date: Fri, 28 Oct 2022 14:57:10 -0400 Message-Id: <20221028185712.79863-3-jlayton@kernel.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221028185712.79863-1-jlayton@kernel.org> References: <20221028185712.79863-1-jlayton@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org The filecache refcounting is a bit non-standard for something searchable by RCU, in that we maintain a sentinel reference while it's hashed. This in turn requires that we have to do things differently in the "put" depending on whether its hashed, which we believe to have led to races. There are other problems in here too. nfsd_file_close_inode_sync can end up freeing an nfsd_file while there are still outstanding references to it, and there are a number of subtle ToC/ToU races. Rework the code so that the refcount is what drives the lifecycle. When the refcount goes to zero, then unhash and rcu free the object. With this change, the LRU carries a reference. Take special care to deal with it when removing an entry from the list. Signed-off-by: Jeff Layton --- fs/nfsd/filecache.c | 357 ++++++++++++++++++++++---------------------- fs/nfsd/trace.h | 5 +- 2 files changed, 178 insertions(+), 184 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index f8ebbf7daa18..d928c5e38eeb 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -1,6 +1,12 @@ // SPDX-License-Identifier: GPL-2.0 /* * The NFSD open file cache. + * + * Each nfsd_file is created in response to client activity -- either regular + * file I/O for v2/v3, or opening a file for v4. Files opened via v4 are + * cleaned up as soon as their refcount goes to 0. Entries for v2/v3 are + * flagged with NFSD_FILE_GC. On their last put, they are added to the LRU for + * eventual disposal if they aren't used again within a short time period. */ #include @@ -301,55 +307,22 @@ nfsd_file_alloc(struct nfsd_file_lookup_key *key, unsigned int may) if (key->gc) __set_bit(NFSD_FILE_GC, &nf->nf_flags); nf->nf_inode = key->inode; - /* nf_ref is pre-incremented for hash table */ - refcount_set(&nf->nf_ref, 2); + refcount_set(&nf->nf_ref, 1); nf->nf_may = key->need; nf->nf_mark = NULL; } return nf; } -static bool -nfsd_file_free(struct nfsd_file *nf) -{ - s64 age = ktime_to_ms(ktime_sub(ktime_get(), nf->nf_birthtime)); - bool flush = false; - - this_cpu_inc(nfsd_file_releases); - this_cpu_add(nfsd_file_total_age, age); - - trace_nfsd_file_put_final(nf); - if (nf->nf_mark) - nfsd_file_mark_put(nf->nf_mark); - if (nf->nf_file) { - get_file(nf->nf_file); - filp_close(nf->nf_file, NULL); - fput(nf->nf_file); - flush = true; - } - - /* - * If this item is still linked via nf_lru, that's a bug. - * WARN and leak it to preserve system stability. - */ - if (WARN_ON_ONCE(!list_empty(&nf->nf_lru))) - return flush; - - call_rcu(&nf->nf_rcu, nfsd_file_slab_free); - return flush; -} - -static bool -nfsd_file_check_writeback(struct nfsd_file *nf) +static void +nfsd_file_fsync(struct nfsd_file *nf) { struct file *file = nf->nf_file; - struct address_space *mapping; if (!file || !(file->f_mode & FMODE_WRITE)) - return false; - mapping = file->f_mapping; - return mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) || - mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK); + return; + if (vfs_fsync(file, 1) != 0) + nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id)); } static int @@ -362,30 +335,6 @@ nfsd_file_check_write_error(struct nfsd_file *nf) return filemap_check_wb_err(file->f_mapping, READ_ONCE(file->f_wb_err)); } -static void -nfsd_file_flush(struct nfsd_file *nf) -{ - struct file *file = nf->nf_file; - - if (!file || !(file->f_mode & FMODE_WRITE)) - return; - if (vfs_fsync(file, 1) != 0) - nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id)); -} - -static void nfsd_file_lru_add(struct nfsd_file *nf) -{ - set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags); - if (list_lru_add(&nfsd_file_lru, &nf->nf_lru)) - trace_nfsd_file_lru_add(nf); -} - -static void nfsd_file_lru_remove(struct nfsd_file *nf) -{ - if (list_lru_del(&nfsd_file_lru, &nf->nf_lru)) - trace_nfsd_file_lru_del(nf); -} - static void nfsd_file_hash_remove(struct nfsd_file *nf) { @@ -408,53 +357,66 @@ nfsd_file_unhash(struct nfsd_file *nf) } static void -nfsd_file_unhash_and_dispose(struct nfsd_file *nf, struct list_head *dispose) +nfsd_file_free(struct nfsd_file *nf) { - trace_nfsd_file_unhash_and_dispose(nf); - if (nfsd_file_unhash(nf)) { - /* caller must call nfsd_file_dispose_list() later */ - nfsd_file_lru_remove(nf); - list_add(&nf->nf_lru, dispose); + s64 age = ktime_to_ms(ktime_sub(ktime_get(), nf->nf_birthtime)); + + trace_nfsd_file_free(nf); + + this_cpu_inc(nfsd_file_releases); + this_cpu_add(nfsd_file_total_age, age); + + nfsd_file_unhash(nf); + nfsd_file_fsync(nf); + + if (nf->nf_mark) + nfsd_file_mark_put(nf->nf_mark); + if (nf->nf_file) { + get_file(nf->nf_file); + filp_close(nf->nf_file, NULL); + fput(nf->nf_file); } + + /* + * If this item is still linked via nf_lru, that's a bug. + * WARN and leak it to preserve system stability. + */ + if (WARN_ON_ONCE(!list_empty(&nf->nf_lru))) + return; + + call_rcu(&nf->nf_rcu, nfsd_file_slab_free); } -static void -nfsd_file_put_noref(struct nfsd_file *nf) +static bool +nfsd_file_check_writeback(struct nfsd_file *nf) { - trace_nfsd_file_put(nf); + struct file *file = nf->nf_file; + struct address_space *mapping; - if (refcount_dec_and_test(&nf->nf_ref)) { - WARN_ON(test_bit(NFSD_FILE_HASHED, &nf->nf_flags)); - nfsd_file_lru_remove(nf); - nfsd_file_free(nf); - } + if (!file || !(file->f_mode & FMODE_WRITE)) + return false; + mapping = file->f_mapping; + return mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) || + mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK); } -static void -nfsd_file_unhash_and_put(struct nfsd_file *nf) +static bool nfsd_file_lru_add(struct nfsd_file *nf) { - if (nfsd_file_unhash(nf)) - nfsd_file_put_noref(nf); + set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags); + if (list_lru_add(&nfsd_file_lru, &nf->nf_lru)) { + trace_nfsd_file_lru_add(nf); + return true; + } + return false; } -void -nfsd_file_put(struct nfsd_file *nf) +static bool nfsd_file_lru_remove(struct nfsd_file *nf) { - might_sleep(); - - if (test_bit(NFSD_FILE_GC, &nf->nf_flags)) - nfsd_file_lru_add(nf); - else if (refcount_read(&nf->nf_ref) == 2) - nfsd_file_unhash_and_put(nf); - - if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) { - nfsd_file_flush(nf); - nfsd_file_put_noref(nf); - } else if (nf->nf_file && test_bit(NFSD_FILE_GC, &nf->nf_flags)) { - nfsd_file_put_noref(nf); - nfsd_file_schedule_laundrette(); - } else - nfsd_file_put_noref(nf); + if (list_lru_del(&nfsd_file_lru, &nf->nf_lru)) { + trace_nfsd_file_lru_del(nf); + return true; + } + return false; } struct nfsd_file * @@ -465,36 +427,77 @@ nfsd_file_get(struct nfsd_file *nf) return NULL; } -static void -nfsd_file_dispose_list(struct list_head *dispose) +/** + * nfsd_file_unhash_and_queue - unhash a file and queue it to the dispose list + * @nf: nfsd_file to be unhashed and queued + * @dispose: list to which it should be queued + * + * Attempt to unhash a nfsd_file and queue it to the given list. Each file + * will have a reference held on behalf of the list. That reference may come + * from the LRU, or we may need to take one. If we can't get a reference, + * ignore it altogether. + */ +static bool +nfsd_file_unhash_and_queue(struct nfsd_file *nf, struct list_head *dispose) { - struct nfsd_file *nf; + trace_nfsd_file_unhash_and_queue(nf); + if (nfsd_file_unhash(nf)) { + /* + * If we remove it from the LRU, then just use that + * reference for the dispose list. Otherwise, we need + * to take a reference. If that fails, just ignore + * the file altogether. + */ + if (!nfsd_file_lru_remove(nf) && !nfsd_file_get(nf)) + return false; + list_add(&nf->nf_lru, dispose); + return true; + } + return false; +} - while(!list_empty(dispose)) { - nf = list_first_entry(dispose, struct nfsd_file, nf_lru); - list_del_init(&nf->nf_lru); - nfsd_file_flush(nf); - nfsd_file_put_noref(nf); +/** + * nfsd_file_put - put the reference to a nfsd_file + * @nf: nfsd_file of which to put the reference + * + * Put a reference to a nfsd_file. In the v4 case, we just put the + * reference immediately. In the v2/3 case, if the reference would be + * the last one, the put it on the LRU instead to be cleaned up later. + */ +void +nfsd_file_put(struct nfsd_file *nf) +{ + trace_nfsd_file_put(nf); + + /* + * The HASHED check is racy. We may end up with the occasional + * unhashed entry on the LRU, but they should get cleaned up + * like any other. + */ + if (test_bit(NFSD_FILE_GC, &nf->nf_flags) && + test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) { + /* + * If this is the last reference (nf_ref == 1), then transfer + * it to the LRU. If the add to the LRU fails, just put it as + * usual. + */ + if (refcount_dec_not_one(&nf->nf_ref) || nfsd_file_lru_add(nf)) + return; } + if (refcount_dec_and_test(&nf->nf_ref)) + nfsd_file_free(nf); } static void -nfsd_file_dispose_list_sync(struct list_head *dispose) +nfsd_file_dispose_list(struct list_head *dispose) { - bool flush = false; struct nfsd_file *nf; while(!list_empty(dispose)) { nf = list_first_entry(dispose, struct nfsd_file, nf_lru); list_del_init(&nf->nf_lru); - nfsd_file_flush(nf); - if (!refcount_dec_and_test(&nf->nf_ref)) - continue; - if (nfsd_file_free(nf)) - flush = true; + nfsd_file_free(nf); } - if (flush) - flush_delayed_fput(); } static void @@ -564,21 +567,8 @@ nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru, struct list_head *head = arg; struct nfsd_file *nf = list_entry(item, struct nfsd_file, nf_lru); - /* - * Do a lockless refcount check. The hashtable holds one reference, so - * we look to see if anything else has a reference, or if any have - * been put since the shrinker last ran. Those don't get unhashed and - * released. - * - * Note that in the put path, we set the flag and then decrement the - * counter. Here we check the counter and then test and clear the flag. - * That order is deliberate to ensure that we can do this locklessly. - */ - if (refcount_read(&nf->nf_ref) > 1) { - list_lru_isolate(lru, &nf->nf_lru); - trace_nfsd_file_gc_in_use(nf); - return LRU_REMOVED; - } + /* We should only be dealing with v2/3 entries here */ + WARN_ON_ONCE(!test_bit(NFSD_FILE_GC, &nf->nf_flags)); /* * Don't throw out files that are still undergoing I/O or @@ -589,40 +579,30 @@ nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru, return LRU_SKIP; } + /* If it was recently added to the list, skip it */ if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags)) { trace_nfsd_file_gc_referenced(nf); return LRU_ROTATE; } - if (!test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) { - trace_nfsd_file_gc_hashed(nf); - return LRU_SKIP; + /* + * Put the reference held on behalf of the LRU. If it wasn't the last + * one, then just remove it from the LRU and ignore it. + */ + if (!refcount_dec_and_test(&nf->nf_ref)) { + trace_nfsd_file_gc_in_use(nf); + list_lru_isolate(lru, &nf->nf_lru); + return LRU_REMOVED; } + /* Refcount went to zero. Unhash it and queue it to the dispose list */ + nfsd_file_unhash(nf); list_lru_isolate_move(lru, &nf->nf_lru, head); this_cpu_inc(nfsd_file_evictions); trace_nfsd_file_gc_disposed(nf); return LRU_REMOVED; } -/* - * Unhash items on @dispose immediately, then queue them on the - * disposal workqueue to finish releasing them in the background. - * - * cel: Note that between the time list_lru_shrink_walk runs and - * now, these items are in the hash table but marked unhashed. - * Why release these outside of lru_cb ? There's no lock ordering - * problem since lru_cb currently takes no lock. - */ -static void nfsd_file_gc_dispose_list(struct list_head *dispose) -{ - struct nfsd_file *nf; - - list_for_each_entry(nf, dispose, nf_lru) - nfsd_file_hash_remove(nf); - nfsd_file_dispose_list_delayed(dispose); -} - static void nfsd_file_gc(void) { @@ -632,7 +612,7 @@ nfsd_file_gc(void) ret = list_lru_walk(&nfsd_file_lru, nfsd_file_lru_cb, &dispose, list_lru_count(&nfsd_file_lru)); trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru)); - nfsd_file_gc_dispose_list(&dispose); + nfsd_file_dispose_list_delayed(&dispose); } static void @@ -657,7 +637,7 @@ nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc) ret = list_lru_shrink_walk(&nfsd_file_lru, sc, nfsd_file_lru_cb, &dispose); trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru)); - nfsd_file_gc_dispose_list(&dispose); + nfsd_file_dispose_list_delayed(&dispose); return ret; } @@ -668,8 +648,11 @@ static struct shrinker nfsd_file_shrinker = { }; /* - * Find all cache items across all net namespaces that match @inode and - * move them to @dispose. The lookup is atomic wrt nfsd_file_acquire(). + * Find all cache items across all net namespaces that match @inode, unhash + * them, take references and then put them on @dispose if that was successful. + * + * The nfsd_file objects on the list will be unhashed, and each will have a + * reference taken. */ static unsigned int __nfsd_file_close_inode(struct inode *inode, struct list_head *dispose) @@ -687,52 +670,59 @@ __nfsd_file_close_inode(struct inode *inode, struct list_head *dispose) nfsd_file_rhash_params); if (!nf) break; - nfsd_file_unhash_and_dispose(nf, dispose); - count++; + + if (nfsd_file_unhash_and_queue(nf, dispose)) + count++; } while (1); rcu_read_unlock(); return count; } /** - * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file + * nfsd_file_close_inode - attempt a delayed close of a nfsd_file * @inode: inode of the file to attempt to remove * - * Unhash and put, then flush and fput all cache items associated with @inode. + * Unhash and put all cache item associated with @inode. */ -void -nfsd_file_close_inode_sync(struct inode *inode) +static unsigned int +nfsd_file_close_inode(struct inode *inode) { - LIST_HEAD(dispose); + struct nfsd_file *nf; unsigned int count; + LIST_HEAD(dispose); count = __nfsd_file_close_inode(inode, &dispose); - trace_nfsd_file_close_inode_sync(inode, count); - nfsd_file_dispose_list_sync(&dispose); + trace_nfsd_file_close_inode(inode, count); + if (count) { + while(!list_empty(&dispose)) { + nf = list_first_entry(&dispose, struct nfsd_file, nf_lru); + list_del_init(&nf->nf_lru); + trace_nfsd_file_closing(nf); + if (refcount_dec_and_test(&nf->nf_ref)) + nfsd_file_free(nf); + } + } + return count; } /** - * nfsd_file_close_inode - attempt a delayed close of a nfsd_file + * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file * @inode: inode of the file to attempt to remove * - * Unhash and put all cache item associated with @inode. + * Unhash and put, then flush and fput all cache items associated with @inode. */ -static void -nfsd_file_close_inode(struct inode *inode) +void +nfsd_file_close_inode_sync(struct inode *inode) { - LIST_HEAD(dispose); - unsigned int count; - - count = __nfsd_file_close_inode(inode, &dispose); - trace_nfsd_file_close_inode(inode, count); - nfsd_file_dispose_list_delayed(&dispose); + if (nfsd_file_close_inode(inode)) + flush_delayed_fput(); } /** * nfsd_file_delayed_close - close unused nfsd_files * @work: dummy * - * Walk the LRU list and close any entries that have not been used since + * Walk the LRU list and destroy any entries that have not been used since * the last scan. */ static void @@ -890,7 +880,7 @@ __nfsd_file_cache_purge(struct net *net) while (!IS_ERR_OR_NULL(nf)) { if (net && nf->nf_net != net) continue; - nfsd_file_unhash_and_dispose(nf, &dispose); + nfsd_file_unhash_and_queue(nf, &dispose); nf = rhashtable_walk_next(&iter); } @@ -1054,8 +1044,10 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, rcu_read_lock(); nf = rhashtable_lookup(&nfsd_file_rhash_tbl, &key, nfsd_file_rhash_params); - if (nf) - nf = nfsd_file_get(nf); + if (nf) { + if (!nfsd_file_lru_remove(nf)) + nf = nfsd_file_get(nf); + } rcu_read_unlock(); if (nf) goto wait_for_construction; @@ -1090,11 +1082,11 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, goto out; } open_retry = false; - nfsd_file_put_noref(nf); + if (refcount_dec_and_test(&nf->nf_ref)) + nfsd_file_free(nf); goto retry; } - nfsd_file_lru_remove(nf); this_cpu_inc(nfsd_file_cache_hits); status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags)); @@ -1104,7 +1096,8 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, this_cpu_inc(nfsd_file_acquisitions); *pnf = nf; } else { - nfsd_file_put(nf); + if (refcount_dec_and_test(&nf->nf_ref)) + nfsd_file_free(nf); nf = NULL; } @@ -1131,7 +1124,7 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, * then unhash. */ if (status != nfs_ok || key.inode->i_nlink == 0) - nfsd_file_unhash_and_put(nf); + nfsd_file_unhash(nf); clear_bit_unlock(NFSD_FILE_PENDING, &nf->nf_flags); smp_mb__after_atomic(); wake_up_bit(&nf->nf_flags, NFSD_FILE_PENDING); diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h index b09ab4f92d43..a44ded06af87 100644 --- a/fs/nfsd/trace.h +++ b/fs/nfsd/trace.h @@ -903,10 +903,11 @@ DEFINE_EVENT(nfsd_file_class, name, \ TP_PROTO(struct nfsd_file *nf), \ TP_ARGS(nf)) -DEFINE_NFSD_FILE_EVENT(nfsd_file_put_final); +DEFINE_NFSD_FILE_EVENT(nfsd_file_free); DEFINE_NFSD_FILE_EVENT(nfsd_file_unhash); DEFINE_NFSD_FILE_EVENT(nfsd_file_put); -DEFINE_NFSD_FILE_EVENT(nfsd_file_unhash_and_dispose); +DEFINE_NFSD_FILE_EVENT(nfsd_file_closing); +DEFINE_NFSD_FILE_EVENT(nfsd_file_unhash_and_queue); TRACE_EVENT(nfsd_file_alloc, TP_PROTO( From patchwork Fri Oct 28 18:57:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 13024223 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 6F9C8ECAAA1 for ; Fri, 28 Oct 2022 18:57:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229975AbiJ1S5T (ORCPT ); Fri, 28 Oct 2022 14:57:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229455AbiJ1S5S (ORCPT ); Fri, 28 Oct 2022 14:57:18 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98BBA1D2B51 for ; Fri, 28 Oct 2022 11:57:17 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 3820562A26 for ; Fri, 28 Oct 2022 18:57:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3EDB9C43470; Fri, 28 Oct 2022 18:57:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666983436; bh=NJmStmbj9UXmkjFc0+Ec0WT9PNFAnNPfSrmtnQZ5jFY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q9WAS2KgoswbDz16wXiy6IchkH7G5dDMRb7tmEfuQM+3T6RgJWjCJNVlp2YZeJunL 9KlsbR201V04kYx+RHrQst72e+8JtqRIzbpdfM/ajUSHkdmtDDwmC6xSTRg5UYrzVn oHpVft1mqj3Twsx/5/71fp4++WHgTQCI7GC2pUEND0envsM3xMSMFvNLPa/a6bPn3i YHHuewirylsAOPukbRm4N3mnYNNljexJLqBnkKwZokDRQK2QlRe7llDA9RvdL6iCr2 khCRwSq/r9HePS5hcetJJvA4wtpqptGvqapEEwB1dfjyBKxz6+FFHNklzvbQKqCy4H OQnUvJggP/Pvg== From: Jeff Layton To: chuck.lever@oracle.com Cc: linux-nfs@vger.kernel.org, neilb@suse.de Subject: [PATCH v3 3/4] nfsd: close race between unhashing and LRU addition Date: Fri, 28 Oct 2022 14:57:11 -0400 Message-Id: <20221028185712.79863-4-jlayton@kernel.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221028185712.79863-1-jlayton@kernel.org> References: <20221028185712.79863-1-jlayton@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org The list_lru_add and list_lru_del functions use list_empty checks to see whether the object is already on the LRU. That's fine in most cases, but we occasionally repurpose nf_lru after unhashing. It's possible for an LRU removal to remove it from a different list altogether if we lose a race. Add a new NFSD_FILE_LRU flag, which indicates that the object actually resides on the LRU and not some other list. Use that when adding and removing it from the LRU instead of just relying on list_empty checks. Add an extra HASHED check after adding the entry to the LRU. If it's now clear, just remove it from the LRU again and put the reference if that remove is successful. Signed-off-by: Jeff Layton --- fs/nfsd/filecache.c | 44 +++++++++++++++++++++++++++++--------------- fs/nfsd/filecache.h | 1 + 2 files changed, 30 insertions(+), 15 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index d928c5e38eeb..47cdc6129a7b 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -403,18 +403,22 @@ nfsd_file_check_writeback(struct nfsd_file *nf) static bool nfsd_file_lru_add(struct nfsd_file *nf) { set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags); - if (list_lru_add(&nfsd_file_lru, &nf->nf_lru)) { - trace_nfsd_file_lru_add(nf); - return true; + if (!test_and_set_bit(NFSD_FILE_LRU, &nf->nf_flags)) { + if (list_lru_add(&nfsd_file_lru, &nf->nf_lru)) { + trace_nfsd_file_lru_add(nf); + return true; + } } return false; } static bool nfsd_file_lru_remove(struct nfsd_file *nf) { - if (list_lru_del(&nfsd_file_lru, &nf->nf_lru)) { - trace_nfsd_file_lru_del(nf); - return true; + if (test_and_clear_bit(NFSD_FILE_LRU, &nf->nf_flags)) { + if (list_lru_del(&nfsd_file_lru, &nf->nf_lru)) { + trace_nfsd_file_lru_del(nf); + return true; + } } return false; } @@ -469,20 +473,30 @@ nfsd_file_put(struct nfsd_file *nf) { trace_nfsd_file_put(nf); - /* - * The HASHED check is racy. We may end up with the occasional - * unhashed entry on the LRU, but they should get cleaned up - * like any other. - */ if (test_bit(NFSD_FILE_GC, &nf->nf_flags) && test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) { /* - * If this is the last reference (nf_ref == 1), then transfer - * it to the LRU. If the add to the LRU fails, just put it as - * usual. + * If this is the last reference (nf_ref == 1), then try to + * transfer it to the LRU. */ - if (refcount_dec_not_one(&nf->nf_ref) || nfsd_file_lru_add(nf)) + if (refcount_dec_not_one(&nf->nf_ref)) return; + + /* Try to add it to the LRU. If that fails, decrement. */ + if (nfsd_file_lru_add(nf)) { + /* If it's still hashed, we're done */ + if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) + return; + + /* + * We're racing with unhashing, so try to remove it from + * the LRU. If removal fails, then someone else already + * has our reference and we're done. If it succeeds, + * fall through to decrement. + */ + if (!nfsd_file_lru_remove(nf)) + return; + } } if (refcount_dec_and_test(&nf->nf_ref)) nfsd_file_free(nf); diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h index b7efb2c3ddb1..e52ab7d5a44c 100644 --- a/fs/nfsd/filecache.h +++ b/fs/nfsd/filecache.h @@ -39,6 +39,7 @@ struct nfsd_file { #define NFSD_FILE_PENDING (1) #define NFSD_FILE_REFERENCED (2) #define NFSD_FILE_GC (3) +#define NFSD_FILE_LRU (4) /* file is on LRU */ unsigned long nf_flags; struct inode *nf_inode; /* don't deref */ refcount_t nf_ref; From patchwork Fri Oct 28 18:57:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 13024225 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 2FA56FA3743 for ; Fri, 28 Oct 2022 18:57:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229917AbiJ1S5V (ORCPT ); Fri, 28 Oct 2022 14:57:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55128 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230115AbiJ1S5U (ORCPT ); Fri, 28 Oct 2022 14:57:20 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D312A1D2B58 for ; Fri, 28 Oct 2022 11:57:18 -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 8F767B82C88 for ; Fri, 28 Oct 2022 18:57:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7B3DC433D6; Fri, 28 Oct 2022 18:57:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666983437; bh=Fh57O2isAT251Px6qkrQwR+hkIPHdB8ywH4ZqCZZ5ig=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PeYOB/G1p1bIUN6+jk4jdlTRMBMOVgRD0in7Ml4R53g7R9b/ZzYGfDifU/fAwRJmn +UNBbVjLajeCMKBckQCAP0KeGU4Ss3FjMxLop1WXhR/XtkiKx+hRZl+9S5//yDME47 m5mMpu9vcqvea1NWkuV1ifUG4+izfhE87MBJ937Uf6gmf/QjQOAPZ7vnugYf+p36tK +PMO+ismYjIaq90MxBkNylDbcYgBIWfHAHWymq1fNH/DB72C0YtQzE6YICUy7cetMU QnfW6dyfbtWXxbyczn189XT4OPv2TzKRL6DVXc+bOwe4zlMIbvoWAZRBVEOSgzKv7r dMgdTN0PTLcCg== From: Jeff Layton To: chuck.lever@oracle.com Cc: linux-nfs@vger.kernel.org, neilb@suse.de Subject: [PATCH v3 4/4] nfsd: start non-blocking writeback after adding nfsd_file to the LRU Date: Fri, 28 Oct 2022 14:57:12 -0400 Message-Id: <20221028185712.79863-5-jlayton@kernel.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221028185712.79863-1-jlayton@kernel.org> References: <20221028185712.79863-1-jlayton@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org When a GC entry gets added to the LRU, kick off SYNC_NONE writeback so that we can be ready to close it when the time comes. This should help minimize delays when freeing objects reaped from the LRU. Signed-off-by: Jeff Layton --- fs/nfsd/filecache.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 47cdc6129a7b..c43b6cff03e2 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -325,6 +325,20 @@ nfsd_file_fsync(struct nfsd_file *nf) nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id)); } +static void +nfsd_file_flush(struct nfsd_file *nf) +{ + struct file *file = nf->nf_file; + struct address_space *mapping; + + if (!file || !(file->f_mode & FMODE_WRITE)) + return; + + mapping = file->f_mapping; + if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) + filemap_flush(mapping); +} + static int nfsd_file_check_write_error(struct nfsd_file *nf) { @@ -484,9 +498,14 @@ nfsd_file_put(struct nfsd_file *nf) /* Try to add it to the LRU. If that fails, decrement. */ if (nfsd_file_lru_add(nf)) { - /* If it's still hashed, we're done */ - if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) + /* + * If it's still hashed, we can just return now, + * after kicking off SYNC_NONE writeback. + */ + if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) { + nfsd_file_flush(nf); return; + } /* * We're racing with unhashing, so try to remove it from