On Tue, Dec 16, 2008 at 03:16:10PM -0500, bfields wrote:
> On Tue, Dec 16, 2008 at 08:43:52PM +0100, Miklos Szeredi wrote:
> > On Tue, 2008-12-16 at 12:39 -0500, J. Bruce Fields wrote:
> > > More precisely, it looks like this started with
> > >
> > > bde74e4bc64415b142e "locks: add special return value for
> > > asynchronous locks"
> > >
> > > But I haven't had the chance to look any harder yet. Miklos? Is this
> > > easy for you to reproduce?
> >
> > Not immediately, at the moment I don't have NFS set up. But if you
> > don't beat me to it, I'll look into this.
>
> OK, thanks. I'll take another look too when I get the chance, so let me
> know of any partial result.
>
> It may just for example be returning the wrong error to the client on an
> nlm blocking lock request, so that the client assumes the lock is gone
> and goes away rather than waiting for a grant request.
Sorry, I've gotten a bit backlogged, but I finally got back to this. If
there's no objections, the following is what I intend to submit.
--b.
commit cb8b864ea6addd3a3e72fe835aafecec63f06cbd
Author: J. Bruce Fields <bfields@xxxxxxxxxxxxxxxx>
Date: Wed Feb 4 17:35:38 2009 -0500
lockd: fix regression in lockd's handling of blocked locks
If a client requests a blocking lock, is denied, then requests it again,
then here in nlmsvc_lock() we will call vfs_lock_file() without FL_SLEEP
set, because we've already queued a block and don't need the locks code
to do it again.
But that means vfs_lock_file() will return -EAGAIN instead of
FILE_LOCK_DENIED. So we still need to translate that -EAGAIN return
into a nlm_lck_blocked error in this case, and put ourselves back on
lockd's block list.
The bug was introduced by bde74e4bc64415b1 "locks: add special return
value for asynchronous locks".
Thanks to From: Frank van Maarseveen for the report; his original test
case was essentially
for i in `seq 30`; do flock /nfsmount/foo sleep 10 & done
Cc: Frank van Maarseveen <frankvm@xxxxxxxxxxx>
Cc: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index 6063a8e..763b78a 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -427,7 +427,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
goto out;
case -EAGAIN:
ret = nlm_lck_denied;
- goto out;
+ break;
case FILE_LOCK_DEFERRED:
if (wait)
break;
@@ -443,6 +443,10 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
goto out;
}
+ ret = nlm_lck_denied;
+ if (!wait)
+ goto out;
+
ret = nlm_lck_blocked;
/* Append to list of blocked */
--
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