[PULL 10/20] block: make BlockLimits::max_pdiscard 64bit

[Eric Blake <eblake@redhat.com>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We are going to support 64 bit discard requests. Now update the
limit variable. It's absolutely safe. The variable is set in some
drivers, and used in bdrv_co_pdiscard().

Update also max_pdiscard variable in bdrv_co_pdiscard(), so that
bdrv_co_pdiscard() is now prepared for 64bit requests. The remaining
logic including num, offset and bytes variables is already
supporting 64bit requests.

So the only thing that prevents 64 bit requests is limiting
max_pdiscard variable to INT_MAX in bdrv_co_pdiscard().
We'll drop this limitation after updating all block drivers.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210903102807.27127-10-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/block_int.h | 11 ++++++-----
 block/io.c                |  3 ++-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index d518703e3e59..9b4e0748bc86 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -674,11 +674,12 @@ typedef struct BlockLimits {
      * otherwise. */
     uint32_t request_alignment;

-    /* Maximum number of bytes that can be discarded at once (since it
-     * is signed, it must be < 2G, if set). Must be multiple of
-     * pdiscard_alignment, but need not be power of 2. May be 0 if no
-     * inherent 32-bit limit */
-    int32_t max_pdiscard;
+    /*
+     * Maximum number of bytes that can be discarded at once. Must be multiple
+     * of pdiscard_alignment, but need not be power of 2. May be 0 if no
+     * inherent 64-bit limit.
+     */
+    int64_t max_pdiscard;

     /* Optimal alignment for discard requests in bytes. A power of 2
      * is best but not mandatory.  Must be a multiple of
diff --git a/block/io.c b/block/io.c
index e40462742ea1..3846e2ed961b 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3056,7 +3056,8 @@ int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
                                   int64_t bytes)
 {
     BdrvTrackedRequest req;
-    int max_pdiscard, ret;
+    int ret;
+    int64_t max_pdiscard;
     int head, tail, align;
     BlockDriverState *bs = child->bs;

-- 
2.31.1