[v4,06/23] qemu-img: Switch get_block_status() to byte-based

Message ID 20170913160333.23622-7-eblake@redhat.com
State New
Headers show
Series
  • make bdrv_get_block_status byte-based
Related show

Commit Message

Eric Blake Sept. 13, 2017, 4:03 p.m.
We are gradually converting to byte-based interfaces, as they are
easier to reason about than sector-based.  Continue by converting
an internal function (no semantic change), and simplifying its
caller accordingly.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
---
v2-v3: no change
---
 qemu-img.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

Comments

John Snow Sept. 26, 2017, 7:16 p.m. | #1
On 09/13/2017 12:03 PM, Eric Blake wrote:
> We are gradually converting to byte-based interfaces, as they are
> easier to reason about than sector-based.  Continue by converting
> an internal function (no semantic change), and simplifying its
> caller accordingly.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>

Patch

diff --git a/qemu-img.c b/qemu-img.c
index 0c12e1c240..54f7682069 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2670,14 +2670,16 @@  static void dump_map_entry(OutputFormat output_format, MapEntry *e,
     }
 }

-static int get_block_status(BlockDriverState *bs, int64_t sector_num,
-                            int nb_sectors, MapEntry *e)
+static int get_block_status(BlockDriverState *bs, int64_t offset,
+                            int64_t bytes, MapEntry *e)
 {
     int64_t ret;
     int depth;
     BlockDriverState *file;
     bool has_offset;
+    int nb_sectors = bytes >> BDRV_SECTOR_BITS;

+    assert(bytes < INT_MAX);
     /* As an optimization, we could cache the current range of unallocated
      * clusters in each file of the chain, and avoid querying the same
      * range repeatedly.
@@ -2685,8 +2687,8 @@  static int get_block_status(BlockDriverState *bs, int64_t sector_num,

     depth = 0;
     for (;;) {
-        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &nb_sectors,
-                                    &file);
+        ret = bdrv_get_block_status(bs, offset >> BDRV_SECTOR_BITS, nb_sectors,
+                                    &nb_sectors, &file);
         if (ret < 0) {
             return ret;
         }
@@ -2706,7 +2708,7 @@  static int get_block_status(BlockDriverState *bs, int64_t sector_num,
     has_offset = !!(ret & BDRV_BLOCK_OFFSET_VALID);

     *e = (MapEntry) {
-        .start = sector_num * BDRV_SECTOR_SIZE,
+        .start = offset,
         .length = nb_sectors * BDRV_SECTOR_SIZE,
         .data = !!(ret & BDRV_BLOCK_DATA),
         .zero = !!(ret & BDRV_BLOCK_ZERO),
@@ -2836,16 +2838,12 @@  static int img_map(int argc, char **argv)

     length = blk_getlength(blk);
     while (curr.start + curr.length < length) {
-        int64_t nsectors_left;
-        int64_t sector_num;
-        int n;
-
-        sector_num = (curr.start + curr.length) >> BDRV_SECTOR_BITS;
+        int64_t offset = curr.start + curr.length;
+        int64_t n;

         /* Probe up to 1 GiB at a time.  */
-        nsectors_left = DIV_ROUND_UP(length, BDRV_SECTOR_SIZE) - sector_num;
-        n = MIN(1 << (30 - BDRV_SECTOR_BITS), nsectors_left);
-        ret = get_block_status(bs, sector_num, n, &next);
+        n = QEMU_ALIGN_DOWN(MIN(1 << 30, length - offset), BDRV_SECTOR_SIZE);
+        ret = get_block_status(bs, offset, n, &next);

         if (ret < 0) {
             error_report("Could not read file metadata: %s", strerror(-ret));