block: change discard to co_discard

Since coroutine operation is now mandatory, convert both bdrv_discard
implementations to coroutines.  For qcow2, this means taking the lock
around the operation.  raw-posix remains synchronous.

The bdrv_discard callback is then unused and can be eliminated.
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block.c

@@ -2962,8 +2962,6 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
             qemu_coroutine_yield();
             return co.ret;
         }
-    } else if (bs->drv->bdrv_discard) {
-        return bs->drv->bdrv_discard(bs, sector_num, nb_sectors);
     } else {
         return 0;
     }

block/qcow2.c

@@ -978,11 +978,17 @@ static int qcow2_make_empty(BlockDriverState *bs)
     return 0;
 }
 
-static int qcow2_discard(BlockDriverState *bs, int64_t sector_num,
-    int nb_sectors)
+static coroutine_fn int qcow2_co_discard(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors)
 {
-    return qcow2_discard_clusters(bs, sector_num << BDRV_SECTOR_BITS,
+    int ret;
+    BDRVQcowState *s = bs->opaque;
+
+    qemu_co_mutex_lock(&s->lock);
+    ret = qcow2_discard_clusters(bs, sector_num << BDRV_SECTOR_BITS,
         nb_sectors);
+    qemu_co_mutex_unlock(&s->lock);
+    return ret;
 }
 
 static int qcow2_truncate(BlockDriverState *bs, int64_t offset)
@@ -1239,7 +1245,7 @@ static BlockDriver bdrv_qcow2 = {
     .bdrv_co_writev     = qcow2_co_writev,
     .bdrv_co_flush      = qcow2_co_flush,
 
-    .bdrv_discard           = qcow2_discard,
+    .bdrv_co_discard        = qcow2_co_discard,
     .bdrv_truncate          = qcow2_truncate,
     .bdrv_write_compressed  = qcow2_write_compressed,
 

block/raw-posix.c

@@ -602,7 +602,8 @@ static int xfs_discard(BDRVRawState *s, int64_t sector_num, int nb_sectors)
 }
 #endif
 
-static int raw_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors)
+static coroutine_fn int raw_co_discard(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors)
 {
 #ifdef CONFIG_XFS
     BDRVRawState *s = bs->opaque;
@@ -632,7 +633,7 @@ static BlockDriver bdrv_file = {
     .bdrv_file_open = raw_open,
     .bdrv_close = raw_close,
     .bdrv_create = raw_create,
-    .bdrv_discard = raw_discard,
+    .bdrv_co_discard = raw_co_discard,
 
     .bdrv_aio_readv = raw_aio_readv,
     .bdrv_aio_writev = raw_aio_writev,

block_int.h

@@ -62,8 +62,6 @@ struct BlockDriver {
                       const uint8_t *buf, int nb_sectors);
     void (*bdrv_close)(BlockDriverState *bs);
     int (*bdrv_create)(const char *filename, QEMUOptionParameter *options);
-    int (*bdrv_discard)(BlockDriverState *bs, int64_t sector_num,
-                        int nb_sectors);
     int (*bdrv_is_allocated)(BlockDriverState *bs, int64_t sector_num,
                              int nb_sectors, int *pnum);
     int (*bdrv_set_key)(BlockDriverState *bs, const char *key);