[Qemu-devel] [PATCH v2 5/5] linux-aio: simplify removal of completed iocbs from the list

[Paolo Bonzini <pbonzini@redhat.com>]

There is no need to do another O(n) pass on the list; the iocb to
split the list at is already available through the array we passed to
io_submit.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/linux-aio.c    | 12 ++++++------
 include/qemu/queue.h | 11 +++++++++++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/block/linux-aio.c b/block/linux-aio.c
index 8474378..c991443 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -186,9 +186,10 @@ static void ioq_init(LaioQueue *io_q)
 
 static void ioq_submit(struct qemu_laio_state *s)
 {
-    int ret, i, len;
+    int ret, len;
     struct qemu_laiocb *aiocb;
     struct iocb *iocbs[MAX_QUEUED_IO];
+    QSIMPLEQ_HEAD(, qemu_laiocb) completed;
 
     do {
         len = 0;
@@ -201,16 +202,15 @@ static void ioq_submit(struct qemu_laio_state *s)
 
         ret = io_submit(s->ctx, len, iocbs);
         if (ret == -EAGAIN) {
-            ret = 0;
+            break;
         }
         if (ret < 0) {
             abort();
         }
 
-        for (i = 0; i < ret; i++) {
-            s->io_q.n--;
-            QSIMPLEQ_REMOVE_HEAD(&s->io_q.pending, next);
-        }
+        s->io_q.n -= ret;
+        aiocb = container_of(iocbs[ret - 1], struct qemu_laiocb, iocb);
+        QSIMPLEQ_SPLIT_AFTER(&s->io_q.pending, aiocb, next, &completed);
     } while (ret == len && !QSIMPLEQ_EMPTY(&s->io_q.pending));
     s->io_q.blocked = (s->io_q.n > 0);
 }
diff --git a/include/qemu/queue.h b/include/qemu/queue.h
index 0dedd29..a98eb3a 100644
--- a/include/qemu/queue.h
+++ b/include/qemu/queue.h
@@ -279,6 +279,17 @@ struct {                                                                \
         (head)->sqh_last = &(head)->sqh_first;                          \
 } while (/*CONSTCOND*/0)
 
+#define QSIMPLEQ_SPLIT_AFTER(head, elm, field, removed) do {            \
+    QSIMPLEQ_INIT(removed);                                             \
+    if (((removed)->sqh_first = (head)->sqh_first) != NULL) {           \
+        if (((head)->sqh_first = (elm)->field.sqe_next) == NULL) {      \
+            (head)->sqh_last = &(head)->sqh_first;                      \
+        }                                                               \
+        (removed)->sqh_last = &(elm)->field.sqe_next;                   \
+        (elm)->field.sqe_next = NULL;                                   \
+    }                                                                   \
+} while (/*CONSTCOND*/0)
+
 #define QSIMPLEQ_REMOVE(head, elm, type, field) do {                    \
     if ((head)->sqh_first == (elm)) {                                   \
         QSIMPLEQ_REMOVE_HEAD((head), field);                            \
-- 
2.1.0