this patch shortens requests to end at an aligned sector so that
the next request starts aligned.
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Peter Lieven <p...@kamp.de>
---
qemu-img.c | 34 ++++++++++++++++++++++++----------
1 file changed, 24 insertions(+), 10 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index 15f423b..9bb1f6f 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1124,8 +1124,7 @@ out3:
static int img_convert(int argc, char **argv)
{
- int c, n, n1, bs_n, bs_i, compress, cluster_size,
- cluster_sectors, skip_create;
+ int c, n, n1, bs_n, bs_i, compress, cluster_sectors, skip_create;
int64_t ret = 0;
int progress = 0, flags;
const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
@@ -1397,19 +1396,21 @@ static int img_convert(int argc, char **argv)
}
}
+ cluster_sectors = 0;
+ ret = bdrv_get_info(out_bs, &bdi);
+ if (ret < 0 && compress) {
+ error_report("could not get block driver info");
+ goto out;
+ } else {
+ cluster_sectors = bdi.cluster_size / BDRV_SECTOR_SIZE;
+ }
+
if (compress) {
- ret = bdrv_get_info(out_bs, &bdi);
- if (ret < 0) {
- error_report("could not get block driver info");
- goto out;
- }
- cluster_size = bdi.cluster_size;
- if (cluster_size <= 0 || cluster_size > bufsectors * BDRV_SECTOR_SIZE)
{
+ if (cluster_sectors <= 0 || cluster_sectors > bufsectors) {
error_report("invalid cluster size");
ret = -1;
goto out;
}
- cluster_sectors = cluster_size >> 9;
sector_num = 0;
nb_sectors = total_sectors;
@@ -1542,6 +1543,19 @@ static int img_convert(int argc, char **argv)
}
n = MIN(nb_sectors, bufsectors);
+
+ /* round down request length to an aligned sector, but
+ * do not bother doing this on short requests. They happen
+ * when we found an all-zero area, and the next sector to
+ * write will not be sector_num + n. */
+ if (cluster_sectors > 0 && n >= cluster_sectors) {
+ int64_t next_aligned_sector = (sector_num + n);
+ next_aligned_sector -= next_aligned_sector % cluster_sectors;
+ if (sector_num + n > next_aligned_sector) {
+ n = next_aligned_sector - sector_num;
+ }
+ }
+
n = MIN(n, bs_sectors - (sector_num - bs_offset));
n1 = n;
--
1.7.9.5
