block: Add blk_co_truncate()

Also convert blk_truncate() into a generated_co_wrapper.

Signed-off-by: Alberto Faria <afaria@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220705161527.1054072-17-afaria@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

block/block-backend.c

@@ -2293,8 +2293,9 @@ int coroutine_fn blk_co_pwrite_compressed(BlockBackend *blk, int64_t offset,
                                BDRV_REQ_WRITE_COMPRESSED);
 }
 
-int blk_truncate(BlockBackend *blk, int64_t offset, bool exact,
-                 PreallocMode prealloc, BdrvRequestFlags flags, Error **errp)
+int coroutine_fn blk_co_truncate(BlockBackend *blk, int64_t offset, bool exact,
+                                 PreallocMode prealloc, BdrvRequestFlags flags,
+                                 Error **errp)
 {
     IO_OR_GS_CODE();
     if (!blk_is_available(blk)) {
@@ -2302,7 +2303,7 @@ int blk_truncate(BlockBackend *blk, int64_t offset, bool exact,
         return -ENOMEDIUM;
     }
 
-    return bdrv_truncate(blk->root, offset, exact, prealloc, flags, errp);
+    return bdrv_co_truncate(blk->root, offset, exact, prealloc, flags, errp);
 }
 
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,

include/sysemu/block-backend-io.h

@@ -182,7 +182,11 @@ int generated_co_wrapper blk_pwrite_zeroes(BlockBackend *blk, int64_t offset,
                                            BdrvRequestFlags flags);
 int coroutine_fn blk_co_pwrite_zeroes(BlockBackend *blk, int64_t offset,
                                       int64_t bytes, BdrvRequestFlags flags);
-int blk_truncate(BlockBackend *blk, int64_t offset, bool exact,
-                 PreallocMode prealloc, BdrvRequestFlags flags, Error **errp);
+int generated_co_wrapper blk_truncate(BlockBackend *blk, int64_t offset,
+                                      bool exact, PreallocMode prealloc,
+                                      BdrvRequestFlags flags, Error **errp);
+int coroutine_fn blk_co_truncate(BlockBackend *blk, int64_t offset, bool exact,
+                                 PreallocMode prealloc, BdrvRequestFlags flags,
+                                 Error **errp);
 
 #endif /* BLOCK_BACKEND_IO_H */

tests/unit/test-block-iothread.c

@@ -298,6 +298,19 @@ static void test_sync_op_truncate(BdrvChild *c)
     c->bs->open_flags |= BDRV_O_RDWR;
 }
 
+static void test_sync_op_blk_truncate(BlockBackend *blk)
+{
+    int ret;
+
+    /* Normal success path */
+    ret = blk_truncate(blk, 65536, false, PREALLOC_MODE_OFF, 0, NULL);
+    g_assert_cmpint(ret, ==, 0);
+
+    /* Early error: Negative offset */
+    ret = blk_truncate(blk, -2, false, PREALLOC_MODE_OFF, 0, NULL);
+    g_assert_cmpint(ret, ==, -EINVAL);
+}
+
 static void test_sync_op_block_status(BdrvChild *c)
 {
     int ret;
@@ -425,6 +438,7 @@ const SyncOpTest sync_op_tests[] = {
     }, {
         .name   = "/sync-op/truncate",
         .fn     = test_sync_op_truncate,
+        .blkfn  = test_sync_op_blk_truncate,
     }, {
         .name   = "/sync-op/block_status",
         .fn     = test_sync_op_block_status,