block: Convert bdrv_get_block_status_above() to bytes

We are gradually moving away from sector-based interfaces, towards
byte-based.  In the common case, allocation is unlikely to ever use
values that are not naturally sector-aligned, but it is possible
that byte-based values will let us be more precise about allocation
at the end of an unaligned file that can do byte-based access.

Changing the name of the function from bdrv_get_block_status_above()
to bdrv_block_status_above() ensures that the compiler enforces that
all callers are updated.  Likewise, since it a byte interface allows
an offset mapping that might not be sector aligned, split the mapping
out of the return value and into a pass-by-reference parameter.  For
now, the io.c layer still assert()s that all uses are sector-aligned,
but that can be relaxed when a later patch implements byte-based
block status in the drivers.

For the most part this patch is just the addition of scaling at the
callers followed by inverse scaling at bdrv_block_status(), plus
updates for the new split return interface.  But some code,
particularly bdrv_block_status(), gets a lot simpler because it no
longer has to mess with sectors.  Likewise, mirror code no longer
computes s->granularity >> BDRV_SECTOR_BITS, and can therefore drop
an assertion about alignment because the loop no longer depends on
alignment (never mind that we don't really have a driver that
reports sub-sector alignments, so it's not really possible to test
the effect of sub-sector mirroring).  Fix a neighboring assertion to
use is_power_of_2 while there.

For ease of review, bdrv_get_block_status() was tackled separately.

Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 12 insertions, 18 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 795be673e7..29d0a50955 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2974,8 +2974,8 @@ finish:
 
 static bool is_zero(BlockDriverState *bs, int64_t offset, int64_t bytes)
 {
-    int nr;
-    int64_t res;
+    int64_t nr;
+    int res;
     int64_t start;
 
     /* TODO: Widening to sector boundaries should only be needed as
@@ -2991,10 +2991,8 @@ static bool is_zero(BlockDriverState *bs, int64_t offset, int64_t bytes)
     if (!bytes) {
         return true;
     }
-    res = bdrv_get_block_status_above(bs, NULL, start >> BDRV_SECTOR_BITS,
-                                      bytes >> BDRV_SECTOR_BITS, &nr, NULL);
-    return res >= 0 && (res & BDRV_BLOCK_ZERO) &&
-        nr * BDRV_SECTOR_SIZE == bytes;
+    res = bdrv_block_status_above(bs, NULL, start, bytes, &nr, NULL, NULL);
+    return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == bytes;
 }
 
 static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs,
@@ -3700,17 +3698,14 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
             required = virtual_size;
         } else {
             int64_t offset;
-            int pnum = 0;
+            int64_t pnum = 0;
 
-            for (offset = 0; offset < ssize;
-                 offset += pnum * BDRV_SECTOR_SIZE) {
-                int nb_sectors = MIN(ssize - offset,
-                                     BDRV_REQUEST_MAX_BYTES) / BDRV_SECTOR_SIZE;
-                int64_t ret;
+            for (offset = 0; offset < ssize; offset += pnum) {
+                int ret;
 
-                ret = bdrv_get_block_status_above(in_bs, NULL,
-                                                  offset >> BDRV_SECTOR_BITS,
-                                                  nb_sectors, &pnum, NULL);
+                ret = bdrv_block_status_above(in_bs, NULL, offset,
+                                              ssize - offset, &pnum, NULL,
+                                              NULL);
                 if (ret < 0) {
                     error_setg_errno(&local_err, -ret,
                                      "Unable to get block status");
@@ -3722,11 +3717,10 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
                 } else if ((ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED)) ==
                            (BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED)) {
                     /* Extend pnum to end of cluster for next iteration */
-                    pnum = (ROUND_UP(offset + pnum * BDRV_SECTOR_SIZE,
-                                 cluster_size) - offset) >> BDRV_SECTOR_BITS;
+                    pnum = ROUND_UP(offset + pnum, cluster_size) - offset;
 
                     /* Count clusters we've seen */
-                    required += offset % cluster_size + pnum * BDRV_SECTOR_SIZE;
+                    required += offset % cluster_size + pnum;
                 }
             }
         }