[Qemu-devel] [PATCH v5 05/23] block: Switch bdrv_make_zero() to byte-based

[Eric Blake <eblake@redhat.com>]

We are gradually converting to byte-based interfaces, as they are
easier to reason about than sector-based.  Change the internal
loop iteration of zeroing a device to track by bytes instead of
sectors (although we are still guaranteed that we iterate by steps
that are sector-aligned).

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>

---
v3-v5: no change
v2: rebase to earlier changes
---
 block/io.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/block/io.c b/block/io.c
index e4d5d33805..afba2da1c4 100644
--- a/block/io.c
+++ b/block/io.c
@@ -696,38 +696,38 @@ int bdrv_pwrite_zeroes(BdrvChild *child, int64_t offset,
  */
 int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
 {
-    int64_t target_sectors, ret, nb_sectors, sector_num = 0;
+    int64_t target_size, ret, bytes, offset = 0;
     BlockDriverState *bs = child->bs;
-    int n;
+    int n; /* sectors */

-    target_sectors = bdrv_nb_sectors(bs);
-    if (target_sectors < 0) {
-        return target_sectors;
+    target_size = bdrv_getlength(bs);
+    if (target_size < 0) {
+        return target_size;
     }

     for (;;) {
-        nb_sectors = MIN(target_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS);
-        if (nb_sectors <= 0) {
+        bytes = MIN(target_size - offset, BDRV_REQUEST_MAX_BYTES);
+        if (bytes <= 0) {
             return 0;
         }
-        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, NULL);
+        ret = bdrv_get_block_status(bs, offset >> BDRV_SECTOR_BITS,
+                                    bytes >> BDRV_SECTOR_BITS, &n, NULL);
         if (ret < 0) {
-            error_report("error getting block status at sector %" PRId64 ": %s",
-                         sector_num, strerror(-ret));
+            error_report("error getting block status at offset %" PRId64 ": %s",
+                         offset, strerror(-ret));
             return ret;
         }
         if (ret & BDRV_BLOCK_ZERO) {
-            sector_num += n;
+            offset += n * BDRV_SECTOR_BITS;
             continue;
         }
-        ret = bdrv_pwrite_zeroes(child, sector_num << BDRV_SECTOR_BITS,
-                                 n << BDRV_SECTOR_BITS, flags);
+        ret = bdrv_pwrite_zeroes(child, offset, n * BDRV_SECTOR_SIZE, flags);
         if (ret < 0) {
-            error_report("error writing zeroes at sector %" PRId64 ": %s",
-                         sector_num, strerror(-ret));
+            error_report("error writing zeroes at offset %" PRId64 ": %s",
+                         offset, strerror(-ret));
             return ret;
         }
-        sector_num += n;
+        offset += n * BDRV_SECTOR_SIZE;
     }
 }

-- 
2.13.6