block: Convert bdrv_discard() to byte-based

Another step towards byte-based interfaces everywhere.  Replace
the sector-based bdrv_discard() with a new byte-based
bdrv_pdiscard(), which silently ignores any unaligned head
or tail.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1468624988-423-3-git-send-email-eblake@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

3 files changed, 12 insertions, 14 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index d982cf9..83b6407 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1512,7 +1512,8 @@ int blk_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
         return ret;
     }
 
-    return bdrv_discard(blk_bs(blk), sector_num, nb_sectors);
+    return bdrv_pdiscard(blk_bs(blk), sector_num << BDRV_SECTOR_BITS,
+                         nb_sectors << BDRV_SECTOR_BITS);
 }
 
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
diff --git a/block/io.c b/block/io.c
index 14d448d..8d41305 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2391,16 +2391,15 @@ int bdrv_flush(BlockDriverState *bs)
 
 typedef struct DiscardCo {
     BlockDriverState *bs;
-    int64_t sector_num;
-    int nb_sectors;
+    int64_t offset;
+    int count;
     int ret;
 } DiscardCo;
-static void coroutine_fn bdrv_discard_co_entry(void *opaque)
+static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque)
 {
     DiscardCo *rwco = opaque;
 
-    rwco->ret = bdrv_co_pdiscard(rwco->bs, rwco->sector_num << BDRV_SECTOR_BITS,
-                                 rwco->nb_sectors << BDRV_SECTOR_BITS);
+    rwco->ret = bdrv_co_pdiscard(rwco->bs, rwco->offset, rwco->count);
 }
 
 int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset,
@@ -2495,23 +2494,23 @@ out:
     return ret;
 }
 
-int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors)
+int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int count)
 {
     Coroutine *co;
     DiscardCo rwco = {
         .bs = bs,
-        .sector_num = sector_num,
-        .nb_sectors = nb_sectors,
+        .offset = offset,
+        .count = count,
         .ret = NOT_DONE,
     };
 
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
-        bdrv_discard_co_entry(&rwco);
+        bdrv_pdiscard_co_entry(&rwco);
     } else {
         AioContext *aio_context = bdrv_get_aio_context(bs);
 
-        co = qemu_coroutine_create(bdrv_discard_co_entry, &rwco);
+        co = qemu_coroutine_create(bdrv_pdiscard_co_entry, &rwco);
         qemu_coroutine_enter(co);
         while (rwco.ret == NOT_DONE) {
             aio_poll(aio_context, true);
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 49b6ce6..cbfb3fe 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -615,9 +615,7 @@ void qcow2_process_discards(BlockDriverState *bs, int ret)
 
         /* Discard is optional, ignore the return value */
         if (ret >= 0) {
-            bdrv_discard(bs->file->bs,
-                         d->offset >> BDRV_SECTOR_BITS,
-                         d->bytes >> BDRV_SECTOR_BITS);
+            bdrv_pdiscard(bs->file->bs, d->offset, d->bytes);
         }
 
         g_free(d);