cow: make writes go at a less indecent speed
Only sync once per write, rather than once per sector. Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
parent
276cbc7f2f
commit
26ae980492
19
block/cow.c
19
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;
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue