[PULL 14/15] qemu-io: Utilize 64-bit status during map

[Eric Blake]

The block layer has supported 64-bit block status from drivers since
commit 86a3d5c688 ("block: Add .bdrv_co_block_status() callback",
v2.12) and friends, with individual driver callbacks responsible for
capping things where necessary.  Artificially capping things below 2G
in the qemu-io 'map' command, added in commit d6a644bbfe ("block: Make
bdrv_is_allocated() byte-based", v2.10) is thus no longer necessary.

One way to test this is with qemu-nbd as server on a raw file larger
than 4G (the entire file should show as allocated), plus 'qemu-io -f
raw -c map nbd://localhost --trace=nbd_\*' as client.  Prior to this
patch, the NBD_CMD_BLOCK_STATUS requests are fragmented at 0x7ffffe00
distances; with this patch, the fragmenting changes to 0x7fffffff
(since the NBD protocol is currently still limited to 32-bit
transactions - see block/nbd.c:nbd_client_co_block_status).  Then in
later patches, once I add an NBD extension for a 64-bit block status,
the same map command completes with just one NBD_CMD_BLOCK_STATUS.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20211203231539.3900865-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 qemu-io-cmds.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 46593d632d8f..954955c12fb9 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1993,11 +1993,9 @@ static int map_is_allocated(BlockDriverState *bs, 
int64_t offset,
                             int64_t bytes, int64_t *pnum)
 {
     int64_t num;
-    int num_checked;
     int ret, firstret;

-    num_checked = MIN(bytes, BDRV_REQUEST_MAX_BYTES);
-    ret = bdrv_is_allocated(bs, offset, num_checked, &num);
+    ret = bdrv_is_allocated(bs, offset, bytes, &num);
     if (ret < 0) {
         return ret;
     }
@@ -2009,8 +2007,7 @@ static int map_is_allocated(BlockDriverState *bs, int64_t 
offset,
         offset += num;
         bytes -= num;

-        num_checked = MIN(bytes, BDRV_REQUEST_MAX_BYTES);
-        ret = bdrv_is_allocated(bs, offset, num_checked, &num);
+        ret = bdrv_is_allocated(bs, offset, bytes, &num);
         if (ret == firstret && num) {
             *pnum += num;
         } else {
-- 
2.35.1