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Subject[24/24] svc: Clean up deferred requests on transport destruction
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Tom Tucker <tom@opengridcomputing.com>

commit 22945e4a1c7454c97f5d8aee1ef526c83fef3223 upstream.

A race between svc_revisit and svc_delete_xprt can result in
deferred requests holding references on a transport that can never be
recovered because dead transports are not enqueued for subsequent
processing.

Check for XPT_DEAD in revisit to clean up completing deferrals on a dead
transport and sweep a transport's deferred queue to do the same for queued
but unprocessed deferrals.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: roma1390 <roma1390@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
net/sunrpc/svc_xprt.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -810,6 +810,11 @@ static void svc_age_temp_xprts(unsigned
void svc_delete_xprt(struct svc_xprt *xprt)
{
struct svc_serv *serv = xprt->xpt_server;
+ struct svc_deferred_req *dr;
+
+ /* Only do this once */
+ if (test_and_set_bit(XPT_DEAD, &xprt->xpt_flags))
+ return;

dprintk("svc: svc_delete_xprt(%p)\n", xprt);
xprt->xpt_ops->xpo_detach(xprt);
@@ -824,12 +829,16 @@ void svc_delete_xprt(struct svc_xprt *xp
* while still attached to a queue, the queue itself
* is about to be destroyed (in svc_destroy).
*/
- if (!test_and_set_bit(XPT_DEAD, &xprt->xpt_flags)) {
- BUG_ON(atomic_read(&xprt->xpt_ref.refcount) < 2);
- if (test_bit(XPT_TEMP, &xprt->xpt_flags))
- serv->sv_tmpcnt--;
+ if (test_bit(XPT_TEMP, &xprt->xpt_flags))
+ serv->sv_tmpcnt--;
+
+ for (dr = svc_deferred_dequeue(xprt); dr;
+ dr = svc_deferred_dequeue(xprt)) {
svc_xprt_put(xprt);
+ kfree(dr);
}
+
+ svc_xprt_put(xprt);
spin_unlock_bh(&serv->sv_lock);
}

@@ -875,17 +884,19 @@ static void svc_revisit(struct cache_def
container_of(dreq, struct svc_deferred_req, handle);
struct svc_xprt *xprt = dr->xprt;

- if (too_many) {
+ spin_lock(&xprt->xpt_lock);
+ set_bit(XPT_DEFERRED, &xprt->xpt_flags);
+ if (too_many || test_bit(XPT_DEAD, &xprt->xpt_flags)) {
+ spin_unlock(&xprt->xpt_lock);
+ dprintk("revisit canceled\n");
svc_xprt_put(xprt);
kfree(dr);
return;
}
dprintk("revisit queued\n");
dr->xprt = NULL;
- spin_lock(&xprt->xpt_lock);
list_add(&dr->handle.recent, &xprt->xpt_deferred);
spin_unlock(&xprt->xpt_lock);
- set_bit(XPT_DEFERRED, &xprt->xpt_flags);
svc_xprt_enqueue(xprt);
svc_xprt_put(xprt);
}



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