[libvirt] [PATCH 1/1] storage: Fix a vol-clone bug for ppc64

[Li Zhang]

On 2013年11月07日 18:41, Ján Tomko wrote:
> On 11/07/2013 09:35 AM, Li Zhang wrote:
>> From: Li Zhang <zhlcindy at linux.vnet.ibm.com>
>>
>> vol-clone reports out of memory error with disk type on ppc64.
>>
>> Currently, wbytes is defined as size_t type which is 8 bytes on ppc64,
>> but args's value in ioctl(fd, args..) in kernel is unsigned int.
>> So it will read more 4 bytes by ioctl() with size_t from memory which
>> gets a large number and causes out of memory error.
> On x86_64 size_t is 8 bytes and int is 4 bytes, I guess this is an endianness issue.

It doesn't look like the endianness issue.
It appends more 32 0s to the value.
I need to trace kernel to see how this happens.

Here is what I get on PPC64.
blksz = 0x1000000000000, pbsz = 0x20000000000

Actually, they should be :
blksz = 0x10000, pbsz = 0x200

On x86_64, they can get right value.

>
>> This patch changes size_t to unsigned int to synchronize with kernel.
> The type in the kernel seems to be int:
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/block/ioctl.c#n363
> https://lkml.org/lkml/2013/11/1/620

Ah, you are right, should be int. :)

>
>> Signed-off-by: Li Zhang <zhlcindy at linux.vnet.ibm.com>
>> ---
>>   src/storage/storage_backend.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
>> index 4b1b00d..f510080 100644
>> --- a/src/storage/storage_backend.c
>> +++ b/src/storage/storage_backend.c
>> @@ -135,7 +135,7 @@ virStorageBackendCopyToFD(virStorageVolDefPtr vol,
>>       int amtread = -1;
>>       int ret = 0;
>>       size_t rbytes = READ_BLOCK_SIZE_DEFAULT;
>> -    size_t wbytes = 0;
>> +    unsigned int wbytes = 0;
>>       int interval;
>>       char *zerobuf = NULL;
>>       char *buf = NULL;
>>
> I'll push this with s/unsigned // later, unless someone has a different opinion.

Got it, thanks.

>
> Jan
>