[Qemu-devel] [7109] block-vpc: Don't silently create smaller image than requested

[Aurelien Jarno]

Revision: 7109
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=7109
Author:   aurel32
Date:     2009-04-15 14:42:46 +0000 (Wed, 15 Apr 2009)
Log Message:
-----------
block-vpc: Don't silently create smaller image than requested

The algorithm from the VHD specification for CHS calculation silently limits
images to 127 GB which may confuse a user who requested a larger image. Better
output an error message and abort.

Signed-off-by: Kevin Wolf <address@hidden>
Signed-off-by: Aurelien Jarno <address@hidden>

Modified Paths:
--------------
    trunk/block-vpc.c
    trunk/qemu-img.c

Modified: trunk/block-vpc.c
===================================================================
--- trunk/block-vpc.c   2009-04-15 14:42:30 UTC (rev 7108)
+++ trunk/block-vpc.c   2009-04-15 14:42:46 UTC (rev 7109)
@@ -433,14 +433,16 @@
  *
  * Note that the geometry doesn't always exactly match total_sectors but
  * may round it down.
+ *
+ * Returns 0 on success, -EFBIG if the size is larger than 127 GB
  */
-static void calculate_geometry(int64_t total_sectors, uint16_t* cyls,
+static int calculate_geometry(int64_t total_sectors, uint16_t* cyls,
     uint8_t* heads, uint8_t* secs_per_cyl)
 {
     uint32_t cyls_times_heads;
 
     if (total_sectors > 65535 * 16 * 255)
-        total_sectors = 65535 * 16 * 255;
+        return -EFBIG;
 
     if (total_sectors > 65535 * 16 * 63) {
         *secs_per_cyl = 255;
@@ -470,6 +472,8 @@
     // Note: Rounding up deviates from the Virtual PC behaviour
     // However, we need this to avoid truncating images in qemu-img convert
     *cyls = (cyls_times_heads + *heads - 1) / *heads;
+
+    return 0;
 }
 
 static int vpc_create(const char *filename, int64_t total_sectors,
@@ -493,7 +497,8 @@
         return -EIO;
 
     // Calculate matching total_size and geometry
-    calculate_geometry(total_sectors, &cyls, &heads, &secs_per_cyl);
+    if (calculate_geometry(total_sectors, &cyls, &heads, &secs_per_cyl))
+        return -EFBIG;
     total_sectors = (int64_t) cyls * heads * secs_per_cyl;
 
     // Prepare the Hard Disk Footer

Modified: trunk/qemu-img.c
===================================================================
--- trunk/qemu-img.c    2009-04-15 14:42:30 UTC (rev 7108)
+++ trunk/qemu-img.c    2009-04-15 14:42:46 UTC (rev 7109)
@@ -306,6 +306,8 @@
     if (ret < 0) {
         if (ret == -ENOTSUP) {
             error("Formatting or formatting option not supported for file 
format '%s'", fmt);
+        } else if (ret == -EFBIG) {
+            error("The image size is too large for file format '%s'", fmt);
         } else {
             error("Error while formatting");
         }
@@ -494,6 +496,8 @@
     if (ret < 0) {
         if (ret == -ENOTSUP) {
             error("Formatting not supported for file format '%s'", out_fmt);
+        } else if (ret == -EFBIG) {
+            error("The image size is too large for file format '%s'", out_fmt);
         } else {
             error("Error while formatting '%s'", out_filename);
         }