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svc: Clean up deferred requests on transport destruction 

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>
This commit is contained in:
Tom Tucker 2009-01-05 15:21:19 -06:00 committed by J. Bruce Fields
parent 9a8d248e2d
commit 22945e4a1c
1 changed files with 18 additions and 7 deletions
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25
net/sunrpc/svc_xprt.c
View File

@ -850,6 +850,11 @@ static void svc_age_temp_xprts(unsigned long closure)
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);
@ -864,12 +869,16 @@ void svc_delete_xprt(struct svc_xprt *xprt)
* 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);
}
@ -915,17 +924,19 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
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);
}