[Qemu-devel] [6828] Fix regression introduced by r6824

[Qemu-devel] [6828] Fix regression introduced by r6824

[Anthony Liguori]

Revision: 6828
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6828
Author:   aliguori
Date:     2009-03-13 03:12:03 +0000 (Fri, 13 Mar 2009)
Log Message:
-----------
Fix regression introduced by r6824

The changes introduced by r6824 broke a subtle, and admittedly obscure, aspect
of the block API.  While bdrv_{pread,pwrite} return the number of bytes read
or written upon success, bdrv_{read,write} returns a zero upon success.

When using bdrv_pread for bdrv_read, special care must be taken to handle this
case.

This fixes certain guest images (notably linux-0.2 provided on the qemu
website).

Reported-by: malc <av1474@comtv.ru>
Reported-by: Herve Poussineau <hpoussin@reactos.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Modified Paths:
--------------
    trunk/block-raw-posix.c
    trunk/block-raw-win32.c

Modified: trunk/block-raw-posix.c
===================================================================
--- trunk/block-raw-posix.c	2009-03-12 20:25:12 UTC (rev 6827)
+++ trunk/block-raw-posix.c	2009-03-13 03:12:03 UTC (rev 6828)
@@ -361,7 +361,12 @@
 static int raw_read(BlockDriverState *bs, int64_t sector_num,
                     uint8_t *buf, int nb_sectors)
 {
-    return raw_pread(bs, sector_num * 512, buf, (uint64_t)nb_sectors * 512);
+    int ret;
+
+    ret = raw_pread(bs, sector_num * 512, buf, nb_sectors * 512);
+    if (ret == (nb_sectors * 512))
+        ret = 0;
+    return ret;
 }
 
 /*
@@ -445,7 +450,11 @@
 static int raw_write(BlockDriverState *bs, int64_t sector_num,
                      const uint8_t *buf, int nb_sectors)
 {
-    return raw_pwrite(bs, sector_num * 512, buf, (uint64_t)nb_sectors * 512);
+    int ret;
+    ret = raw_pwrite(bs, sector_num * 512, buf, nb_sectors * 512);
+    if (ret == (nb_sectors * 512))
+        ret = 0;
+    return ret;
 }
 
 #ifdef CONFIG_AIO

Modified: trunk/block-raw-win32.c
===================================================================
--- trunk/block-raw-win32.c	2009-03-12 20:25:12 UTC (rev 6827)
+++ trunk/block-raw-win32.c	2009-03-13 03:12:03 UTC (rev 6828)
@@ -145,6 +145,8 @@
 #endif
             return ret_count;
     }
+    if (ret_count == count)
+        ret_count = 0;
     return ret_count;
 }
 
@@ -171,6 +173,8 @@
 #endif
             return ret_count;
     }
+    if (ret_count == count)
+        ret_count = 0;
     return ret_count;
 }