[Qemu-devel] [PATCH v2] block-vpc: Don't silently create smaller image than requested

[Kevin Wolf <kwolf@redhat.com>]

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Aurelien Jarno schrieb:
> On Wed, Apr 08, 2009 at 04:49:05PM +0200, Kevin Wolf wrote:
>> 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 <kwolf@redhat.com>
>> ---
>>  block-vpc.c |    9 ++++++---
>>  qemu-img.c  |    4 ++++
>>  2 files changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/block-vpc.c b/block-vpc.c
>> index 7ae5202..d915d20 100644
>> --- a/block-vpc.c
>> +++ b/block-vpc.c
>> @@ -433,14 +433,16 @@ static int vpc_write(BlockDriverState *bs, int64_t sector_num,
>>   *
>>   * 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
>>   */
> 
> Actually 0 is never returned, leading to a warning:
>   CC    block-vpc.o
> block-vpc.c: In function ‘calculate_geometry’:
> block-vpc.c:475: warning: control reaches end of non-void function

Oops, you're right. I'm pretty sure that it compiled fine when I tested 
it. Maybe forgot to commit or something.

Please find attached a new version which actually contains a return 0.

Kevin

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From 9d612c70ee232443337c79825afd754aad1db878 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 8 Apr 2009 15:44:04 +0200
Subject: [PATCH] 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 <kwolf@redhat.com>
---
 block-vpc.c |   11 ++++++++---
 qemu-img.c  |    4 ++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/block-vpc.c b/block-vpc.c
index 7ae5202..71a171d 100644
--- a/block-vpc.c
+++ b/block-vpc.c
@@ -433,14 +433,16 @@ static int vpc_write(BlockDriverState *bs, int64_t sector_num,
  *
  * 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 @@ static void calculate_geometry(int64_t total_sectors, uint16_t* cyls,
     // 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 @@ static int vpc_create(const char *filename, int64_t total_sectors,
         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
diff --git a/qemu-img.c b/qemu-img.c
index 913ad34..ccf4a6f 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -306,6 +306,8 @@ static int img_create(int argc, char **argv)
     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 @@ static int img_convert(int argc, char **argv)
     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);
         }
-- 
1.6.0.6