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, 9 insertions, 16 deletions

diff --git a/qemu-img.c b/qemu-img.c
index 4cf4d2423d..2dc07e5ac3 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -5120,30 +5120,23 @@ static int img_dd(int argc, char **argv)
     in.buf = g_new(uint8_t, in.bsz);
 
     for (out_pos = 0; in_pos < size; block_count++) {
-        int in_ret, out_ret;
+        int bytes = (in_pos + in.bsz > size) ? size - in_pos : in.bsz;
 
-        if (in_pos + in.bsz > size) {
-            in_ret = blk_pread(blk1, in_pos, in.buf, size - in_pos);
-        } else {
-            in_ret = blk_pread(blk1, in_pos, in.buf, in.bsz);
-        }
-        if (in_ret < 0) {
+        ret = blk_pread(blk1, in_pos, in.buf, bytes);
+        if (ret < 0) {
             error_report("error while reading from input image file: %s",
-                         strerror(-in_ret));
-            ret = -1;
+                         strerror(-ret));
             goto out;
         }
-        in_pos += in_ret;
+        in_pos += bytes;
 
-        out_ret = blk_pwrite(blk2, out_pos, in.buf, in_ret, 0);
-
-        if (out_ret < 0) {
+        ret = blk_pwrite(blk2, out_pos, in.buf, bytes, 0);
+        if (ret < 0) {
             error_report("error while writing to output image file: %s",
-                         strerror(-out_ret));
-            ret = -1;
+                         strerror(-ret));
             goto out;
         }
-        out_pos += out_ret;
+        out_pos += bytes;
     }
 
 out: