We are generally moving to int64_t for both offset and bytes parameters
on all io paths.

Main motivation is realization of 64-bit write_zeroes operation for
fast zeroing large disk chunks, up to the whole disk.

We chose signed type, to be consistent with off_t (which is signed) and
with possibility for signed return type (where negative value means
error).

So, prepare bdrv_co_do_pwrite_zeroes() now.

Callers are safe, as converting int to int64_t is safe. Concentrate on
'bytes' usage in the function (thx to Eric Blake):

    compute 'int tail' via % 'int alignment' - safe
    fragmentation loop 'int num' - still fragments with a cap on
      max_transfer

    use of 'num' within the loop
    MIN(bytes, max_transfer) as well as %alignment - still works, so
         calculations in if (head) {} are safe
    clamp size by 'int max_write_zeroes' - safe
    drv->bdrv_co_pwrite_zeroes(int) - safe because of clamping
    clamp size by 'int max_transfer' - safe
    buf allocation is still clamped to max_transfer
    qemu_iovec_init_buf(size_t) - safe because of clamping
    bdrv_driver_pwritev(uint64_t) - safe

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/block/io.c b/block/io.c
index b2bf18038b..c6a476559a 100644
--- a/block/io.c
+++ b/block/io.c
@@ -41,7 +41,7 @@
 
 static void bdrv_parent_cb_resize(BlockDriverState *bs);
 static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
-    int64_t offset, int bytes, BdrvRequestFlags flags);
+    int64_t offset, int64_t bytes, BdrvRequestFlags flags);
 
 static void bdrv_parent_drained_begin(BlockDriverState *bs, BdrvChild *ignore,
                                       bool ignore_bds_parents)
@@ -1791,7 +1791,7 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
 }
 
 static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
-    int64_t offset, int bytes, BdrvRequestFlags flags)
+    int64_t offset, int64_t bytes, BdrvRequestFlags flags)
 {
     BlockDriver *drv = bs->drv;
     QEMUIOVector qiov;
@@ -1806,6 +1806,8 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
                         bs->bl.request_alignment);
     int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer, MAX_BOUNCE_BUFFER);
 
+    bdrv_check_request(offset, bytes, &error_abort);
+
     if (!drv) {
         return -ENOMEDIUM;
     }
@@ -1821,7 +1823,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
     assert(max_write_zeroes >= bs->bl.request_alignment);
 
     while (bytes > 0 && !ret) {
-        int num = bytes;
+        int64_t num = bytes;
 
         /* Align request.  Block drivers can expect the "bulk" of the request
          * to be aligned, and that unaligned requests do not cross cluster
-- 
2.25.4

On 12/11/20 12:39 PM, Vladimir Sementsov-Ogievskiy wrote:
> We are generally moving to int64_t for both offset and bytes parameters
> on all io paths.
> 
> Main motivation is realization of 64-bit write_zeroes operation for
> fast zeroing large disk chunks, up to the whole disk.
> 
> We chose signed type, to be consistent with off_t (which is signed) and
> with possibility for signed return type (where negative value means
> error).
> 
> So, prepare bdrv_co_do_pwrite_zeroes() now.
> 
> Callers are safe, as converting int to int64_t is safe. Concentrate on
> 'bytes' usage in the function (thx to Eric Blake):
> 
>     compute 'int tail' via % 'int alignment' - safe
>     fragmentation loop 'int num' - still fragments with a cap on
>       max_transfer
> 
>     use of 'num' within the loop
>     MIN(bytes, max_transfer) as well as %alignment - still works, so
>          calculations in if (head) {} are safe
>     clamp size by 'int max_write_zeroes' - safe
>     drv->bdrv_co_pwrite_zeroes(int) - safe because of clamping
>     clamp size by 'int max_transfer' - safe
>     buf allocation is still clamped to max_transfer
>     qemu_iovec_init_buf(size_t) - safe because of clamping
>     bdrv_driver_pwritev(uint64_t) - safe
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/io.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

And thanks for including the gist of my previous audit - that greatly
speeds things up this time through. ;)

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org