From owner-svn-src-head@freebsd.org Sat Oct 17 08:48:33 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 6D3FC42FAF1; Sat, 17 Oct 2020 08:48:33 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4CCxWP2Jnrz3b2K; Sat, 17 Oct 2020 08:48:33 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 32B9B1EE4C; Sat, 17 Oct 2020 08:48:33 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 09H8mXLw063269; Sat, 17 Oct 2020 08:48:33 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 09H8mXHr063268; Sat, 17 Oct 2020 08:48:33 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <202010170848.09H8mXHr063268@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Sat, 17 Oct 2020 08:48:33 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r366784 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 366784 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 17 Oct 2020 08:48:33 -0000 Author: mjg Date: Sat Oct 17 08:48:32 2020 New Revision: 366784 URL: https://svnweb.freebsd.org/changeset/base/366784 Log: cache: remove entries before trying to add new ones, not after Should allow positive entries to replace negative ones in case the cache is full. Modified: head/sys/kern/vfs_cache.c Modified: head/sys/kern/vfs_cache.c ============================================================================== --- head/sys/kern/vfs_cache.c Sat Oct 17 08:47:08 2020 (r366783) +++ head/sys/kern/vfs_cache.c Sat Oct 17 08:48:32 2020 (r366784) @@ -1923,8 +1923,21 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, /* * Avoid blowout in namecache entries. + * + * Bugs: + * 1. filesystems may end up tryng to add an already existing entry + * (for example this can happen after a cache miss during concurrent + * lookup), in which case we will call cache_negative_zap_one despite + * not adding anything. + * 2. the routine may fail to free anything and no provisions are made + * to make it try harder (see the inside for failure modes) + * 3. it only ever looks at negative entries. */ lnumcache = atomic_fetchadd_long(&numcache, 1) + 1; + if (numneg * ncnegfactor > lnumcache) { + cache_negative_zap_one(); + lnumcache = atomic_load_long(&numcache); + } if (__predict_false(lnumcache >= ncsize)) { atomic_subtract_long(&numcache, 1); counter_u64_add(numdrops, 1); @@ -2087,8 +2100,6 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, atomic_store_char(&ncp->nc_flag, ncp->nc_flag & ~NCF_WIP); cache_enter_unlock(&cel); - if (numneg * ncnegfactor > lnumcache) - cache_negative_zap_one(); if (ndd != NULL) cache_free(ndd); return;