[PATCH] v9fs: fix corner cases when flushing request

When v9fs_mux_rpc sends a 9P message, it may be put in the queue of unsent
request.  If the user process receives a signal, v9fs_mux_rpc sets the
request error to ERREQFLUSH and assigns NULL to request's send message.  If
the message was still in the unsent queue, v9fs_write_work would produce an
oops while processing it.

The patch makes sure that requests that are being flushed are moved to the
pending requests queue safely.

If a request is being flushed, don't remove it from the list of pending
requests even if it receives a reply before the flush is acknoledged.  The
request will be removed during from the Rflush handler (v9fs_mux_flush_cb).

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Cc: Eric Van Hensbergen <ericvh@ericvh.myip.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/9p/mux.c b/fs/9p/mux.c
index 945cb36..ea1134e 100644 (file)
--- a/fs/9p/mux.c
+++ b/fs/9p/mux.c
@@ -471,10 +471,13 @@ static void v9fs_write_work(void *a)
                }
 
                spin_lock(&m->lock);
-               req =
-                   list_entry(m->unsent_req_list.next, struct v9fs_req,
+again:
+               req = list_entry(m->unsent_req_list.next, struct v9fs_req,
                               req_list);
                list_move_tail(&req->req_list, &m->req_list);
+               if (req->err == ERREQFLUSH)
+                       goto again;
+
                m->wbuf = req->tcall->sdata;
                m->wsize = req->tcall->size;
                m->wpos = 0;
@@ -525,7 +528,7 @@ static void process_request(struct v9fs_mux_data *m, struct v9fs_req *req)
        struct v9fs_str *ename;
 
        tag = req->tag;
-       if (req->rcall->id == RERROR && !req->err) {
+       if (!req->err && req->rcall->id == RERROR) {
                ecode = req->rcall->params.rerror.errno;
                ename = &req->rcall->params.rerror.error;
 
@@ -551,7 +554,10 @@ static void process_request(struct v9fs_mux_data *m, struct v9fs_req *req)
                        req->err = -EIO;
        }
 
-       if (req->cb && req->err != ERREQFLUSH) {
+       if (req->err == ERREQFLUSH)
+               return;
+
+       if (req->cb) {
                dprintk(DEBUG_MUX, "calling callback tcall %p rcall %p\n",
                        req->tcall, req->rcall);
 
@@ -812,6 +818,7 @@ v9fs_mux_rpc_cb(void *a, struct v9fs_fcall *tc, struct v9fs_fcall *rc, int err)
        struct v9fs_mux_rpc *r;
 
        if (err == ERREQFLUSH) {
+               kfree(rc);
                dprintk(DEBUG_MUX, "err req flush\n");
                return;
        }