218e99
From a1a7f1301c20582d3326e33acd94a4c198c60bcd Mon Sep 17 00:00:00 2001
218e99
From: Paolo Bonzini <pbonzini@redhat.com>
218e99
Date: Fri, 18 Oct 2013 08:14:27 +0200
218e99
Subject: [PATCH 02/81] cow: make writes go at a less indecent speed
218e99
218e99
RH-Author: Paolo Bonzini <pbonzini@redhat.com>
218e99
Message-id: <1382084091-16636-3-git-send-email-pbonzini@redhat.com>
218e99
Patchwork-id: 54985
218e99
O-Subject: [RHEL 7.0 qemu-kvm PATCH 02/26] cow: make writes go at a less indecent speed
218e99
Bugzilla: 989646
218e99
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
218e99
RH-Acked-by: Max Reitz <mreitz@redhat.com>
218e99
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
218e99
218e99
Only sync once per write, rather than once per sector.
218e99
218e99
Reviewed-by: Eric Blake <eblake@redhat.com>
218e99
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
218e99
(cherry picked from commit 26ae980492920e417bc91761cc85950f18e41f85)
218e99
---
218e99
 block/cow.c | 19 ++++++++++++++++---
218e99
 1 file changed, 16 insertions(+), 3 deletions(-)
218e99
218e99
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
218e99
---
218e99
 block/cow.c |   19 ++++++++++++++++---
218e99
 1 files changed, 16 insertions(+), 3 deletions(-)
218e99
218e99
diff --git a/block/cow.c b/block/cow.c
218e99
index c12088b..2f72334 100644
218e99
--- a/block/cow.c
218e99
+++ b/block/cow.c
218e99
@@ -106,7 +106,7 @@ static int cow_open(BlockDriverState *bs, QDict *options, int flags)
218e99
  * XXX(hch): right now these functions are extremely inefficient.
218e99
  * We should just read the whole bitmap we'll need in one go instead.
218e99
  */
218e99
-static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
218e99
+static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum, bool *first)
218e99
 {
218e99
     uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
218e99
     uint8_t bitmap;
218e99
@@ -117,9 +117,21 @@ static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
218e99
        return ret;
218e99
     }
218e99
 
218e99
+    if (bitmap & (1 << (bitnum % 8))) {
218e99
+        return 0;
218e99
+    }
218e99
+
218e99
+    if (*first) {
218e99
+        ret = bdrv_flush(bs->file);
218e99
+        if (ret < 0) {
218e99
+            return ret;
218e99
+        }
218e99
+        *first = false;
218e99
+    }
218e99
+
218e99
     bitmap |= (1 << (bitnum % 8));
218e99
 
218e99
-    ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap));
218e99
+    ret = bdrv_pwrite(bs->file, offset, &bitmap, sizeof(bitmap));
218e99
     if (ret < 0) {
218e99
        return ret;
218e99
     }
218e99
@@ -181,9 +193,10 @@ static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
218e99
 {
218e99
     int error = 0;
218e99
     int i;
218e99
+    bool first = true;
218e99
 
218e99
     for (i = 0; i < nb_sectors; i++) {
218e99
-        error = cow_set_bit(bs, sector_num + i);
218e99
+        error = cow_set_bit(bs, sector_num + i, &first);
218e99
         if (error) {
218e99
             break;
218e99
         }
218e99
-- 
218e99
1.7.1
218e99