block: Make bdrv_{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.

The few callers that rely on the previous behavior are adjusted
accordingly by hand.

Signed-off-by: Alberto Faria <afaria@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20220609152744.3891847-4-afaria@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/block/dmg.c b/block/dmg.c
index 5a460c3..98db18d 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -390,7 +390,7 @@ static int dmg_read_plist_xml(BlockDriverState *bs, DmgHeaderState *ds,
     buffer = g_malloc(info_length + 1);
     buffer[info_length] = '\0';
     ret = bdrv_pread(bs->file, info_begin, info_length, buffer, 0);
-    if (ret != info_length) {
+    if (ret < 0) {
         ret = -EINVAL;
         goto fail;
     }
@@ -611,7 +611,7 @@ static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->compressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
 
@@ -637,7 +637,7 @@ static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->compressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
 
@@ -658,7 +658,7 @@ static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->compressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
 
@@ -674,7 +674,7 @@ static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
         case UDRW: /* copy */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->uncompressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
             break;