On Tue, 19 Aug 2014 18:02:27 +0800 Ian Kent <raven@xxxxxxxxxx> wrote:
> On Mon, 2014-08-18 at 16:25 +0800, Ian Kent wrote:
> > On Mon, 2014-08-18 at 16:33 +1000, NeilBrown wrote:
> > > Hi Ian,
> > > Have you had a chance to run your tests in these patches yet?
> > > I've done what testing I can think of and cannot fault them.
> >
> > I haven't, I've been plagued with illness so I'm not getting nearly
> > enough done. I'll try to put a kernel together and run the test in the
> > next week or so.
>
> Just to let you know that I managed to spend some time on this. I built
> a kernel (3.17.0-rc1) with the series and ran a couple of tests.
>
> I'm not certain that the patches I used are identical to your posting, I
> saw one difference, after the fact, that shouldn't matter, I'll have to
> check that.
>
> It isn't possible to test expire to mount races because the mounts in
> the tree never expire.
>
> At first I thought it was because so many processes were accessing the
> tree all the time but manually constructing the maps and mounting the
> mounts shows that nothing ever expires, at least for this tree.
>
> However, issuing a shut down does expire all the mounts and shuts down
> autofs cleanly.
>
> So there is something not quite right with the expire check or my
> patches have mistakes.
Ahh.. I bet I know what it is.
autofs4_can_expire() isn't idempotent.
Because we call should_expire twice, autofs4_can_expire() is called twice and
the second time it failed because the first time it resets ->last_used.
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index eb4b770a4bf6..80133a9d9427 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -26,6 +26,9 @@ static inline int autofs4_can_expire(struct dentry *dentry,
if (ino == NULL)
return 0;
+ if (ino->flags & AUTOFS_INF_NO_RCU)
+ /* Already performed this test */
+ return 1;
if (!do_now) {
/* Too young to die */
if (!timeout || time_after(ino->last_used + timeout, now))
might fix it, but might be a hack.
(tests.... yep, that seems to fix it).
I'll think some more tomorrow.
Thanks,
NeilBrown
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