[PATCH 9/9] loop: Add LOOP_CONFIGURE ioctl

[Xiaoming Ni]

On 2022/11/18 14:34, Lauri Kasanen wrote:
> On Fri, 18 Nov 2022 09:01:58 +0800
> Xiaoming Ni <nixiaoming at huawei.com> wrote:
> 
>> LOOP_CONFIGURE is added to Linux 5.8
> ...
>> diff --git a/libbb/loop.c b/libbb/loop.c
>> index 9a7ca666d..d4f4906b0 100644
>> --- a/libbb/loop.c
>> +++ b/libbb/loop.c
>> @@ -126,6 +126,30 @@ static int open_file(const char *file, unsigned flags, int *mode)
>>   	return ffd;
>>   }
>>   
>> +#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,8,0)
>> +static int set_loop_configure(int ffd, int lfd, bb_loop_info *loopinfo)
>> +#else
> 
> This assumes compile-time matches runtime. Ie, if you build on a 5.8
> system, but run on an earlier kernel, the resulting busybox would be
> unable to mount loops at all.
> 
> Please put it backward runtime compatibility, probably by having the
> new-kernel code in the same func.
> 

+ rc = ioctl(lfd, LOOP_CONFIGURE, &config);
+ if (rc == 0) {
+         return lfd;
+ }
+ if (rc == -1 && errno == EINVAL) /* The system may not support 
RING_CONFIGURE. */
+         return set_loop_configure_old(ffd, lfd, loopinfo);
+ return -1;

Is this ok?


> - Lauri
> 
> .
>