[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>

1 files changed, 11 insertions, 4 deletions

diff --git a/fs/9p/mux.c b/fs/9p/mux.c
index 945cb368d451..ea1134eb47c8 100644
--- 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;
         }