the current implementation always splits requests if a buffer
begins or ends with zeroes independent of the length of the
zero area. Change this to really only split off zero areas
that have at least a length of 'min' bytes.
Signed-off-by: Peter Lieven <p...@kamp.de>
---
qemu-img.c | 44 ++++++++++++++------------------------------
1 file changed, 14 insertions(+), 30 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index 5df66fe..8e7357d 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1010,45 +1010,29 @@ static int is_allocated_sectors(const uint8_t *buf, int
n, int *pnum)
}
/*
- * Like is_allocated_sectors, but if the buffer starts with a used sector,
- * up to 'min' consecutive sectors containing zeros are ignored. This avoids
- * breaking up write requests for only small sparse areas.
+ * Like is_allocated_sectors, but only at least 'min' consecutive sectors
+ * containing zeros are considered unallocated. This avoids breaking up write
+ * requests for only small sparse areas.
*/
static int is_allocated_sectors_min(const uint8_t *buf, int n, int *pnum,
- int min)
+ int min)
{
- int ret;
- int num_checked, num_used;
-
- if (n < min) {
- min = n;
- }
-
- ret = is_allocated_sectors(buf, n, pnum);
- if (!ret) {
- return ret;
- }
-
- num_used = *pnum;
- buf += BDRV_SECTOR_SIZE * *pnum;
- n -= *pnum;
- num_checked = num_used;
+ int num_used = 0;
while (n > 0) {
- ret = is_allocated_sectors(buf, n, pnum);
-
- buf += BDRV_SECTOR_SIZE * *pnum;
- n -= *pnum;
- num_checked += *pnum;
- if (ret) {
- num_used = num_checked;
- } else if (*pnum >= min) {
+ if (!is_allocated_sectors(buf, n, pnum) && *pnum >= min) {
break;
}
+ num_used += *pnum;
+ buf += BDRV_SECTOR_SIZE * *pnum;
+ n -= *pnum;
}
- *pnum = num_used;
- return 1;
+ if (num_used) {
+ *pnum = num_used;
+ }
+
+ return !!num_used;
}
/*
--
1.9.1
