net/9p: handle correctly interrupted 9P requests

Currently the 9p code crashes when a operation is interrupted, i.e. for
example when the user presses ^C while reading from a file.

This patch fixes the code that is responsible for interruption and flushing
of 9P operations.

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>

1 files changed, 19 insertions, 55 deletions

diff --git a/net/9p/client.c b/net/9p/client.c
index 781d89a952e4..dd43a8289b0d 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -203,7 +203,6 @@ static struct p9_req_t *p9_tag_alloc(struct p9_client *c, u16 tag)
         p9pdu_reset(req->tc);
         p9pdu_reset(req->rc);
 
-        req->flush_tag = 0;
         req->tc->tag = tag-1;
         req->status = REQ_STATUS_ALLOC;
 
@@ -324,35 +323,9 @@ static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
  */
 void p9_client_cb(struct p9_client *c, struct p9_req_t *req)
 {
-        struct p9_req_t *other_req;
-        unsigned long flags;
-
         P9_DPRINTK(P9_DEBUG_MUX, " tag %d\n", req->tc->tag);
-
-        if (req->status == REQ_STATUS_ERROR)
-                wake_up(req->wq);
-
-        if (req->flush_tag) {                   /* flush receive path */
-                P9_DPRINTK(P9_DEBUG_9P, "<<< RFLUSH %d\n", req->tc->tag);
-                spin_lock_irqsave(&c->lock, flags);
-                other_req = p9_tag_lookup(c, req->flush_tag);
-                if (other_req->status != REQ_STATUS_FLSH) /* stale flush */
-                        spin_unlock_irqrestore(&c->lock, flags);
-                else {
-                        other_req->status = REQ_STATUS_FLSHD;
-                        spin_unlock_irqrestore(&c->lock, flags);
-                        wake_up(other_req->wq);
-                }
-                p9_free_req(c, req);
-        } else {                                /* normal receive path */
-                P9_DPRINTK(P9_DEBUG_MUX, "normal: tag %d\n", req->tc->tag);
-                spin_lock_irqsave(&c->lock, flags);
-                if (req->status != REQ_STATUS_FLSHD)
-                        req->status = REQ_STATUS_RCVD;
-                spin_unlock_irqrestore(&c->lock, flags);
-                wake_up(req->wq);
-                P9_DPRINTK(P9_DEBUG_MUX, "wakeup: %d\n", req->tc->tag);
-        }
+        wake_up(req->wq);
+        P9_DPRINTK(P9_DEBUG_MUX, "wakeup: %d\n", req->tc->tag);
 }
 EXPORT_SYMBOL(p9_client_cb);
 
@@ -486,9 +459,15 @@ static int p9_client_flush(struct p9_client *c, struct p9_req_t *oldreq)
         if (IS_ERR(req))
                 return PTR_ERR(req);
 
-        req->flush_tag = oldtag;
 
-        /* we don't free anything here because RPC isn't complete */
+        /* if we haven't received a response for oldreq,
+           remove it from the list. */
+        spin_lock(&c->lock);
+        if (oldreq->status == REQ_STATUS_FLSH)
+                list_del(&oldreq->req_list);
+        spin_unlock(&c->lock);
+
+        p9_free_req(c, req);
         return 0;
 }
 
@@ -509,7 +488,6 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
         struct p9_req_t *req;
         unsigned long flags;
         int sigpending;
-        int flushed = 0;
 
         P9_DPRINTK(P9_DEBUG_MUX, "client %p op %d\n", c, type);
 
@@ -546,42 +524,28 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
                 goto reterr;
         }
 
-        /* if it was a flush we just transmitted, return our tag */
-        if (type == P9_TFLUSH)
-                return req;
-again:
         P9_DPRINTK(P9_DEBUG_MUX, "wait %p tag: %d\n", req->wq, tag);
         err = wait_event_interruptible(*req->wq,
                                                 req->status >= REQ_STATUS_RCVD);
-        P9_DPRINTK(P9_DEBUG_MUX, "wait %p tag: %d returned %d (flushed=%d)\n",
-                                                req->wq, tag, err, flushed);
+        P9_DPRINTK(P9_DEBUG_MUX, "wait %p tag: %d returned %d\n",
+                                                req->wq, tag, err);
 
         if (req->status == REQ_STATUS_ERROR) {
                 P9_DPRINTK(P9_DEBUG_ERROR, "req_status error %d\n", req->t_err);
                 err = req->t_err;
-        } else if (err == -ERESTARTSYS && flushed) {
-                P9_DPRINTK(P9_DEBUG_MUX, "flushed - going again\n");
-                goto again;
-        } else if (req->status == REQ_STATUS_FLSHD) {
-                P9_DPRINTK(P9_DEBUG_MUX, "flushed - erestartsys\n");
-                err = -ERESTARTSYS;
         }
 
-        if ((err == -ERESTARTSYS) && (c->status == Connected) && (!flushed)) {
+        if ((err == -ERESTARTSYS) && (c->status == Connected)) {
                 P9_DPRINTK(P9_DEBUG_MUX, "flushing\n");
-                spin_lock_irqsave(&c->lock, flags);
-                if (req->status == REQ_STATUS_SENT)
-                        req->status = REQ_STATUS_FLSH;
-                spin_unlock_irqrestore(&c->lock, flags);
                 sigpending = 1;
-                flushed = 1;
                 clear_thread_flag(TIF_SIGPENDING);
 
-                if (c->trans_mod->cancel(c, req)) {
-                        err = p9_client_flush(c, req);
-                        if (err == 0)
-                                goto again;
-                }
+                if (c->trans_mod->cancel(c, req))
+                        p9_client_flush(c, req);
+
+                /* if we received the response anyway, don't signal error */
+                if (req->status == REQ_STATUS_RCVD)
+                        err = 0;
         }
 
         if (sigpending) {