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[Qemu-devel] [PATCH v3 02/19] cow: make writes go at a less indecent spe
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH v3 02/19] cow: make writes go at a less indecent speed |
Date: |
Thu, 25 Jul 2013 16:23:00 +0200 |
Only sync once per write, rather than once per sector.
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
block/cow.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/block/cow.c b/block/cow.c
index fa3d41f..9ae2d6a 100644
--- a/block/cow.c
+++ b/block/cow.c
@@ -106,7 +106,7 @@ static int cow_open(BlockDriverState *bs, QDict *options,
int flags)
* XXX(hch): right now these functions are extremely inefficient.
* We should just read the whole bitmap we'll need in one go instead.
*/
-static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
+static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum, bool
*first)
{
uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
uint8_t bitmap;
@@ -117,9 +117,21 @@ static inline int cow_set_bit(BlockDriverState *bs,
int64_t bitnum)
return ret;
}
+ if (bitmap & (1 << (bitnum % 8))) {
+ return 0;
+ }
+
+ if (*first) {
+ ret = bdrv_flush(bs->file);
+ if (ret < 0) {
+ return ret;
+ }
+ *first = false;
+ }
+
bitmap |= (1 << (bitnum % 8));
- ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap));
+ ret = bdrv_pwrite(bs->file, offset, &bitmap, sizeof(bitmap));
if (ret < 0) {
return ret;
}
@@ -181,9 +193,10 @@ static int cow_update_bitmap(BlockDriverState *bs, int64_t
sector_num,
{
int error = 0;
int i;
+ bool first = true;
for (i = 0; i < nb_sectors; i++) {
- error = cow_set_bit(bs, sector_num + i);
+ error = cow_set_bit(bs, sector_num + i, &first);
if (error) {
break;
}
--
1.8.3.1
[Qemu-devel] [PATCH v3 03/19] cow: do not call bdrv_co_is_allocated, Paolo Bonzini, 2013/07/25
[Qemu-devel] [PATCH v3 05/19] block: make bdrv_co_is_allocated static, Paolo Bonzini, 2013/07/25