[Qemu-block] [PATCH v2 09/15] block: Switch bdrv_co_get_block_status() to byte-based

[Eric Blake]

We are gradually converting to byte-based interfaces, as they are
easier to reason about than sector-based.  Convert another internal
function (no semantic change), and as with its public counterpart,
rename to bdrv_co_block_status() to make the compiler enforce that
we catch all uses.  For now, we assert that callers still pass
aligned data, but ultimately, this will be the function where we
hand off to a byte-based driver callback, and will eventually need
to add logic to ensure we round calls according to the driver's
request_alignment then touch up the result handed back to the
caller, to start permitting a caller to pass unaligned offsets.

Signed-off-by: Eric Blake <address@hidden>

---
v2: rebase to earlier changes
---
 block/io.c | 90 ++++++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 53 insertions(+), 37 deletions(-)

diff --git a/block/io.c b/block/io.c
index 2662f37..2d324af 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1721,42 +1721,43 @@ int64_t coroutine_fn 
bdrv_co_get_block_status_from_backing(BlockDriverState *bs,
  * status; this is a hint that a larger 'pnum' result is more
  * important than including BDRV_BLOCK_OFFSET_VALID in the return.
  *
- * If 'sector_num' is beyond the end of the disk image the return value is
+ * If 'offset' is beyond the end of the disk image the return value is
  * BDRV_BLOCK_EOF and 'pnum' is set to 0.
  *
- * 'pnum' is set to the number of sectors (including and immediately following
- * the specified sector) that are known to be in the same
- * allocated/unallocated state.
+ * 'pnum' is set to the number of bytes (including and immediately following
+ * the specified offset) that are known to be in the same
+ * allocated/unallocated state.  It may be NULL.
  *
- * 'nb_sectors' is the max value 'pnum' should be set to.  If nb_sectors goes
+ * 'bytes' is the max value 'pnum' should be set to.  If bytes goes
  * beyond the end of the disk image it will be clamped; if 'pnum' is set to
  * the end of the image, then the returned value will include BDRV_BLOCK_EOF.
  *
  * If returned value is positive, BDRV_BLOCK_OFFSET_VALID bit is set, and
- * 'file' is non-NULL, then '*file' points to the BDS which the sector range
- * is allocated in.
+ * 'file' is non-NULL, then '*file' points to the BDS which owns the
+ * allocated sector that contains offset.
  */
-static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
-                                                     bool allocation,
-                                                     int64_t sector_num,
-                                                     int nb_sectors, int *pnum,
-                                                     BlockDriverState **file)
+static int64_t coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
+                                                 bool allocation,
+                                                 int64_t offset, int64_t bytes,
+                                                 int64_t *pnum,
+                                                 BlockDriverState **file)
 {
-    int64_t total_sectors;
-    int64_t n;
+    int64_t total_size;
+    int64_t n; /* bytes */
     int64_t ret, ret2;
     BlockDriverState *local_file = NULL;
+    int count; /* sectors */

     assert(pnum);
-    total_sectors = bdrv_nb_sectors(bs);
-    if (total_sectors < 0) {
+    total_size = bdrv_getlength(bs);
+    if (total_size < 0) {
         if (file) {
             *file = NULL;
         }
-        return total_sectors;
+        return total_size;
     }

-    if (sector_num >= total_sectors) {
+    if (offset >= total_size) {
         *pnum = 0;
         if (file) {
             *file = NULL;
@@ -1764,19 +1765,19 @@ static int64_t coroutine_fn 
bdrv_co_get_block_status(BlockDriverState *bs,
         return BDRV_BLOCK_EOF;
     }

-    n = total_sectors - sector_num;
-    if (n < nb_sectors) {
-        nb_sectors = n;
+    n = total_size - offset;
+    if (n < bytes) {
+        bytes = n;
     }

     if (!bs->drv->bdrv_co_get_block_status) {
-        *pnum = nb_sectors;
+        *pnum = bytes;
         ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
-        if (sector_num + nb_sectors == total_sectors) {
+        if (offset + bytes == total_size) {
             ret |= BDRV_BLOCK_EOF;
         }
         if (bs->drv->protocol_name) {
-            ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE);
+            ret |= BDRV_BLOCK_OFFSET_VALID | (offset & BDRV_BLOCK_OFFSET_MASK);
             if (file) {
                 *file = bs;
             }
@@ -1787,18 +1788,27 @@ static int64_t coroutine_fn 
bdrv_co_get_block_status(BlockDriverState *bs,
     }

     bdrv_inc_in_flight(bs);
-    ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum,
+    /*
+     * TODO: Rather than require aligned offsets, we could instead
+     * round to the driver's request_alignment here, then touch up
+     * count afterwards back to the caller's expectations.
+     */
+    assert(QEMU_IS_ALIGNED(offset | bytes, BDRV_SECTOR_SIZE));
+    ret = bs->drv->bdrv_co_get_block_status(bs, offset >> BDRV_SECTOR_BITS,
+                                            bytes >> BDRV_SECTOR_BITS, &count,
                                             &local_file);
     if (ret < 0) {
         *pnum = 0;
         goto out;
     }
+    *pnum = count * BDRV_SECTOR_SIZE;

     if (ret & BDRV_BLOCK_RAW) {
         assert(ret & BDRV_BLOCK_OFFSET_VALID && local_file);
-        ret = bdrv_co_get_block_status(local_file, allocation,
-                                       ret >> BDRV_SECTOR_BITS,
-                                       *pnum, pnum, &local_file);
+        ret = bdrv_co_block_status(local_file, allocation,
+                                   ret & BDRV_BLOCK_OFFSET_MASK,
+                                   *pnum, pnum, &local_file);
+        assert(QEMU_IS_ALIGNED(*pnum, BDRV_SECTOR_SIZE));
         goto out;
     }

@@ -1809,8 +1819,8 @@ static int64_t coroutine_fn 
bdrv_co_get_block_status(BlockDriverState *bs,
             ret |= BDRV_BLOCK_ZERO;
         } else if (bs->backing) {
             BlockDriverState *bs2 = bs->backing->bs;
-            int64_t nb_sectors2 = bdrv_nb_sectors(bs2);
-            if (nb_sectors2 >= 0 && sector_num >= nb_sectors2) {
+            int64_t size2 = bdrv_getlength(bs2);
+            if (size2 >= 0 && offset >= size2) {
                 ret |= BDRV_BLOCK_ZERO;
             }
         }
@@ -1819,11 +1829,11 @@ static int64_t coroutine_fn 
bdrv_co_get_block_status(BlockDriverState *bs,
     if (!allocation && local_file && local_file != bs &&
         (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
         (ret & BDRV_BLOCK_OFFSET_VALID)) {
-        int file_pnum;
+        int64_t file_pnum;

-        ret2 = bdrv_co_get_block_status(local_file, true,
-                                        ret >> BDRV_SECTOR_BITS,
-                                        *pnum, &file_pnum, NULL);
+        ret2 = bdrv_co_block_status(local_file, true,
+                                    ret & BDRV_BLOCK_OFFSET_MASK,
+                                    *pnum, &file_pnum, NULL);
         if (ret2 >= 0) {
             /* Ignore errors.  This is just providing extra information, it
              * is useful but not necessary.
@@ -1849,7 +1859,7 @@ out:
         *file = local_file;
     }
     bdrv_dec_in_flight(bs);
-    if (ret >= 0 && sector_num + *pnum == total_sectors) {
+    if (ret >= 0 && offset + *pnum == total_size) {
         ret |= BDRV_BLOCK_EOF;
     }
     return ret;
@@ -1869,11 +1879,17 @@ static int64_t coroutine_fn 
bdrv_co_get_block_status_above(BlockDriverState *bs,

     assert(bs != base);
     for (p = bs; p != base; p = backing_bs(p)) {
-        ret = bdrv_co_get_block_status(p, allocation, sector_num, nb_sectors,
-                                       pnum, file);
+        int64_t count;
+
+        ret = bdrv_co_block_status(p, allocation,
+                                   sector_num * BDRV_SECTOR_SIZE,
+                                   nb_sectors * BDRV_SECTOR_SIZE, &count,
+                                   file);
         if (ret < 0) {
             break;
         }
+        assert(QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE));
+        *pnum = count >> BDRV_SECTOR_BITS;
         if (ret & BDRV_BLOCK_ZERO && ret & BDRV_BLOCK_EOF && !first) {
             /*
              * Reading beyond the end of the file continues to read
-- 
2.9.4