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SubjectRe: [NFSv4] 2.6.23-rc4 oops in nfs4_cb_recall...
From
On Mon, Sep 10, 2007 at 03:39:23PM +0100, Daniel J Blueman wrote:
> On 09/09/2007, J. Bruce Fields <bfields@fieldses.org> wrote:
> > > When accessing a directory inode from a single other client, NFSv4
> > > callbacks catastrophically failed [1] on the NFS server with
> > > 2.6.23-rc4 (unpatched); clients are both 2.6.22 (Ubuntu Gutsy build).
> > > Seems not easy to reproduce, since this kernel was running smoothly
> > > for 7 days on the server.
> > >
> > > What information will help track this down, or is there a known
> > > failure mechanism?
> >
> > I haven't seen that before.
> >
> > > I can map stack frames to source lines with objdump, if that helps.
>
> > If it's still easy, it might help to figure out exactly where in
> > xprt_reserve() it died, and why. If we've got some race that can lead
> > to freeing the client while a callback is in progress, then perhaps this
> > is on the first dereference of xprt?
>
> I've raised the bug report into bugzilla, added other observations
> from a second occurrence recently and disassembled xprt_reserve with
> line numbers.
>
> http://bugzilla.kernel.org/show_bug.cgi?id=9003
>
> Ping me for any more detail/info and thanks!

If you or anyone else that's seen this problem could test the following,
that would be helpful. Thanks!

--b.

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index c1cb7e0..9d536a8 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -486,6 +486,7 @@ out_put_cred:
/* Success or failure, now we're either waiting for lease expiration
* or deleg_return. */
dprintk("NFSD: nfs4_cb_recall: dp %p dl_flock %p dl_count %d\n",dp, dp->dl_flock, atomic_read(&dp->dl_count));
+ put_nfs4_client(clp);
nfs4_put_delegation(dp);
return;
}
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 6256492..6f182d2 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -358,9 +358,22 @@ alloc_client(struct xdr_netobj name)
return clp;
}

+static void
+shutdown_callback_client(struct nfs4_client *clp)
+{
+ struct rpc_clnt *clnt = clp->cl_callback.cb_client;
+
+ /* shutdown rpc client, ending any outstanding recall rpcs */
+ if (clnt) {
+ clp->cl_callback.cb_client = NULL;
+ rpc_shutdown_client(clnt);
+ }
+}
+
static inline void
free_client(struct nfs4_client *clp)
{
+ shutdown_callback_client(clp);
if (clp->cl_cred.cr_group_info)
put_group_info(clp->cl_cred.cr_group_info);
kfree(clp->cl_name.data);
@@ -375,18 +388,6 @@ put_nfs4_client(struct nfs4_client *clp)
}

static void
-shutdown_callback_client(struct nfs4_client *clp)
-{
- struct rpc_clnt *clnt = clp->cl_callback.cb_client;
-
- /* shutdown rpc client, ending any outstanding recall rpcs */
- if (clnt) {
- clp->cl_callback.cb_client = NULL;
- rpc_shutdown_client(clnt);
- }
-}
-
-static void
expire_client(struct nfs4_client *clp)
{
struct nfs4_stateowner *sop;
@@ -396,8 +397,6 @@ expire_client(struct nfs4_client *clp)
dprintk("NFSD: expire_client cl_count %d\n",
atomic_read(&clp->cl_count));

- shutdown_callback_client(clp);
-
INIT_LIST_HEAD(&reaplist);
spin_lock(&recall_lock);
while (!list_empty(&clp->cl_delegations)) {
@@ -1346,6 +1345,7 @@ void nfsd_break_deleg_cb(struct file_lock *fl)
* lock) we know the server hasn't removed the lease yet, we know
* it's safe to take a reference: */
atomic_inc(&dp->dl_count);
+ atomic_inc(&dp->dl_client->cl_count);

spin_lock(&recall_lock);
list_add_tail(&dp->dl_recall_lru, &del_recall_lru);
@@ -1354,8 +1354,12 @@ void nfsd_break_deleg_cb(struct file_lock *fl)
/* only place dl_time is set. protected by lock_kernel*/
dp->dl_time = get_seconds();

- /* XXX need to merge NFSD_LEASE_TIME with fs/locks.c:lease_break_time */
- fl->fl_break_time = jiffies + NFSD_LEASE_TIME * HZ;
+ /*
+ * We don't want the locks code to timeout the lease for us;
+ * we'll remove it ourself if the delegation isn't returned
+ * in time.
+ */
+ fl->fl_break_time = 0;

t = kthread_run(do_recall, dp, "%s", "nfs4_cb_recall");
if (IS_ERR(t)) {
@@ -1364,6 +1368,7 @@ void nfsd_break_deleg_cb(struct file_lock *fl)
printk(KERN_INFO "NFSD: Callback thread failed for "
"for client (clientid %08x/%08x)\n",
clp->cl_clientid.cl_boot, clp->cl_clientid.cl_id);
+ put_nfs4_client(dp->dl_client);
nfs4_put_delegation(dp);
}
}
-
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