[Qemu-devel] [PULL 07/12] 9pfs: only free completed request if not flushed

[Greg Kurz <groug@kaod.org>]

If a PDU has a flush request pending, the current code calls pdu_free()
twice:

1) pdu_complete()->pdu_free() with pdu->cancelled set, which does nothing

2) v9fs_flush()->pdu_free() with pdu->cancelled cleared, which moves the
   PDU back to the free list.

This works but it complexifies the logic of pdu_free().

With this patch, pdu_complete() only calls pdu_free() if no flush request
is pending, i.e. qemu_co_queue_next() returns false.

Since pdu_free() is now supposed to be called with pdu->cancelled cleared,
the check in pdu_free() is dropped and replaced by an assertion.

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/9p.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index df8aa726c9a1..f0dc2ce589cd 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -627,14 +627,10 @@ V9fsPDU *pdu_alloc(V9fsState *s)
 void pdu_free(V9fsPDU *pdu)
 {
     V9fsState *s = pdu->s;
-    /*
-     * Cancelled pdu are added back to the freelist
-     * by flush request .
-     */
-    if (!pdu->cancelled) {
-        QLIST_REMOVE(pdu, next);
-        QLIST_INSERT_HEAD(&s->free_list, pdu, next);
-    }
+
+    g_assert(!pdu->cancelled);
+    QLIST_REMOVE(pdu, next);
+    QLIST_INSERT_HEAD(&s->free_list, pdu, next);
 }
 
 /*
@@ -679,9 +675,9 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
     pdu_push_and_notify(pdu);
 
     /* Now wakeup anybody waiting in flush for this request */
-    qemu_co_queue_next(&pdu->complete);
-
-    pdu_free(pdu);
+    if (!qemu_co_queue_next(&pdu->complete)) {
+        pdu_free(pdu);
+    }
 }
 
 static mode_t v9mode_to_mode(uint32_t mode, V9fsString *extension)
-- 
2.5.5