On 11/09/2015 03:12 PM, Karel Zak wrote:
> On Mon, Nov 09, 2015 at 02:06:26PM +0100, Florian Margaine wrote:
>> Instead of using string functions to extract the device name and reading
>> this file, this patch uses the loop device API through ioctl to get the
>> correct backing file.
>
> #define LO_NAME_SIZE 64
>
> struct loop_info64 {
> ...
> uint8_t lo_file_name[LO_NAME_SIZE];
> };
>
>
> The loopdev is based on file descriptor, the lo_file_name[] is hint
> only and it does not have to match with the real path and the most
> important problem is that it uses 64-bytes buffer.
>
> For losetup we use LOOP_GET_STATUS64 ioctl as fallback solution only.
I was thinking that this kind of code could be used, can you confirm
that this would be fine? Untested code:
static int resolve_loop_device()
{
int ret;
ret = fopen('/sys/...', 'r');
if (ret == NULL)
if (errno == ENOENT)
return resolve_loop_device_ioctl();
}
static int __attribute__((noinline)) resolve_loop_device_ioctl()
{
/* use ioctl */
}
This would use the normal path most of the time, and use the fallback
only if necessary. The 64-bytes buffer issue would be mitigated.
>
> Karel
>
>
--
Florian Margaine
Product Engineer @ Platform.sh
https://platform.sh
https://keybase.io/fmargaine
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