Date: Fri, 31 Jul 2015 10:46:51 -0700 (PDT)
From: Hugh Dickins <hughd@google.com>
To: Al Viro <viro@zeniv.linux.org.uk>
cc: Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: v4.2-rc dcache regression, probably 75a6f82a0d10
Message-ID: <alpine.LSU.2.11.1507311022320.10162@eggly.anvils>
User-Agent: Alpine 2.11 (LSU 23 2013-08-11)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1367
Lines: 28

I think there's something not quite right with the fs/dcache.c
commit 75a6f82a0d10 ("freeing unlinked file indefinitely delayed").

When running my old tmpfs swapping load (two repetitive make -j20
kernel builds, one on tmpfs, one on ext4 over loop over tmpfs file,
in limited memory with plenty of swapping; rm -rf of both trees
in between the builds): one of the builds, always the ext4 so far,
fails after several hours, one or another header file "No such file
or directory", but the file's there when I check the tree afterwards.

Sounds like a dcache problem, and 75a6f82a0d10 seemed the only
likely candidate, so I experimented with reverting it yesterday,
and ran successfully for 24 hours.  That's a little too soon to
be sure (I've set another run going this morning), but I'd say
90% certain that is to blame, and thought I'd better alert you
sooner than later - you'll probably guess what's the matter
long before I get back to check today's run.

(I saw exactly the same symptom two months ago; but that was just
before you put in 2159184ea01e "d_walk() might skip too much",
which fixed it back then.)

Hugh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/