block: Make blk_{pread,pwrite}() return 0 on success

They currently return the value of their 'bytes' parameter on success.

Make them return 0 instead, for consistency with other I/O functions and
in preparation to implement them using generated_co_wrapper. This also
makes it clear that short reads/writes are not possible.

Signed-off-by: Alberto Faria <afaria@redhat.com>
Message-Id: <20220705161527.1054072-2-afaria@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 2f0d8ac25a..443f22c732 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -541,28 +541,34 @@ fail:
 static int do_pread(BlockBackend *blk, char *buf, int64_t offset,
                     int64_t bytes, int64_t *total)
 {
+    int ret;
+
     if (bytes > INT_MAX) {
         return -ERANGE;
     }
 
-    *total = blk_pread(blk, offset, (uint8_t *)buf, bytes);
-    if (*total < 0) {
-        return *total;
+    ret = blk_pread(blk, offset, (uint8_t *)buf, bytes);
+    if (ret < 0) {
+        return ret;
     }
+    *total = bytes;
     return 1;
 }
 
 static int do_pwrite(BlockBackend *blk, char *buf, int64_t offset,
                      int64_t bytes, int flags, int64_t *total)
 {
+    int ret;
+
     if (bytes > INT_MAX) {
         return -ERANGE;
     }
 
-    *total = blk_pwrite(blk, offset, (uint8_t *)buf, bytes, flags);
-    if (*total < 0) {
-        return *total;
+    ret = blk_pwrite(blk, offset, (uint8_t *)buf, bytes, flags);
+    if (ret < 0) {
+        return ret;
     }
+    *total = bytes;
     return 1;
 }