On Wed, 2015-10-07 at 14:57 -0400, Trond Myklebust wrote: > Hi Al, > > Please could you take a look at the bugzilla entry in > https://bugzilla.kernel.org/show_bug.cgi?id=104911 ? > > It describes a NFS caching regression that appears to be caused by > commit 766c4cbfacd8634d7580bac6a1b8456e63de3e84 ("namei: > d_is_negative() should be checked before ->d_seq validation"). > > Shouldn't that test for 'if (negative) return -ENOENT;' happen after > the call to d_revalidate() in lookup_fast()? If not, we can end up > caching negative dentries forever, AFAICS... > > Cheers > Trond Leandro, can you please test if the following patch helps in any way? Cheers Trond 8<----------------------------------------------------------------- >From eb61ece5739bb2f3b6d03dd8ca8e335bf0d12687 Mon Sep 17 00:00:00 2001 From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> Date: Thu, 8 Oct 2015 08:44:00 -0400 Subject: [PATCH] namei: results of d_is_negative() should be checked after dentry revalidation Leandro Awa writes: After switching to version 4.1.6, our parallelized and distributed workflows now fail consistently with errors of the form: T34: ./regex.c:39:22: error: config.h: No such file or directory >From our 'git bisect' testing, the following commit appears to be the possible cause of the behavior we've been seeing: commit 766c4cbfacd8 The issue is that revalidation may cause the dentry to be dropped in NFS if, say, the client notes that the directory timestamps have changed. Reported-by: Leandro Awa <lawa@xxxxxxxxxx> Link: https://bugzilla.kernel.org/show_bug.cgi?id=104911 Fixes: 766c4cbfacd8 ("namei: d_is_negative() should be checked...") Cc: stable@xxxxxxxxxxxxxxx # v4.1+ Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> --- fs/namei.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 726d211db484..33e9495a3129 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1558,8 +1558,6 @@ static int lookup_fast(struct nameidata *nd, negative = d_is_negative(dentry); if (read_seqcount_retry(&dentry->d_seq, seq)) return -ECHILD; - if (negative) - return -ENOENT; /* * This sequence count validates that the parent had no @@ -1580,6 +1578,12 @@ static int lookup_fast(struct nameidata *nd, goto unlazy; } } + /* + * Note: do negative dentry check after revalidation in + * case that drops it. + */ + if (negative) + return -ENOENT; path->mnt = mnt; path->dentry = dentry; if (likely(__follow_mount_rcu(nd, path, inode, seqp))) -- 2.4.3 -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@xxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
