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, 8 insertions, 47 deletions

diff --git a/block/io.c b/block/io.c
index 61b3477..e64b1cb 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2016,7 +2016,7 @@ static int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
     return ret;
 }
 
-/* Coroutine wrapper for bdrv_get_block_status_above() */
+/* Coroutine wrapper for bdrv_block_status_above() */
 static void coroutine_fn bdrv_block_status_above_co_entry(void *opaque)
 {
     BdrvCoBlockStatusData *data = opaque;
@@ -2064,58 +2064,19 @@ static int bdrv_common_block_status_above(BlockDriverState *bs,
     return data.ret;
 }
 
-int64_t bdrv_get_block_status_above(BlockDriverState *bs,
-                                    BlockDriverState *base,
-                                    int64_t sector_num,
-                                    int nb_sectors, int *pnum,
-                                    BlockDriverState **file)
+int bdrv_block_status_above(BlockDriverState *bs, BlockDriverState *base,
+                            int64_t offset, int64_t bytes, int64_t *pnum,
+                            int64_t *map, BlockDriverState **file)
 {
-    int64_t ret;
-    int64_t n;
-    int64_t map;
-
-    ret = bdrv_common_block_status_above(bs, base, true,
-                                         sector_num * BDRV_SECTOR_SIZE,
-                                         nb_sectors * BDRV_SECTOR_SIZE,
-                                         &n, &map, file);
-    if (ret < 0) {
-        *pnum = 0;
-        return ret;
-    }
-    assert(QEMU_IS_ALIGNED(n | map, BDRV_SECTOR_SIZE));
-    *pnum = n >> BDRV_SECTOR_BITS;
-    return ret | map;
+    return bdrv_common_block_status_above(bs, base, true, offset, bytes,
+                                          pnum, map, file);
 }
 
 int bdrv_block_status(BlockDriverState *bs, int64_t offset, int64_t bytes,
                       int64_t *pnum, int64_t *map, BlockDriverState **file)
 {
-    int64_t ret;
-    int n;
-
-    assert(QEMU_IS_ALIGNED(offset | bytes, BDRV_SECTOR_SIZE));
-    assert(pnum);
-    /*
-     * The contract allows us to return pnum smaller than bytes, even
-     * if the next query would see the same status; we truncate the
-     * request to avoid overflowing the driver's 32-bit interface.
-     */
-    bytes = MIN(bytes, BDRV_REQUEST_MAX_BYTES);
-    ret = bdrv_get_block_status_above(bs, backing_bs(bs),
-                                      offset >> BDRV_SECTOR_BITS,
-                                      bytes >> BDRV_SECTOR_BITS, &n, file);
-    if (ret < 0) {
-        assert(INT_MIN <= ret);
-        *pnum = 0;
-        return ret;
-    }
-    *pnum = n * BDRV_SECTOR_SIZE;
-    if (map) {
-        *map = ret & BDRV_BLOCK_OFFSET_MASK;
-    } else {
-        ret &= ~BDRV_BLOCK_OFFSET_VALID;
-    }
-    return ret & ~BDRV_BLOCK_OFFSET_MASK;
+    return bdrv_block_status_above(bs, backing_bs(bs),
+                                   offset, bytes, pnum, map, file);
 }
 
 int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,