Re: [PATCH] loop: Remove redundant status flag operation

[Yang Xu <xuyang2018.jy@cn.fujitsu.com>]

Hi Martijn


> Hi Yang,
> 
> Thanks for the patch! I think it's correct, but I wonder whether it's
> confusing to read, especially since the comment says "For flags that
> can't be cleared, use previous values too" - it might not be obvious
> to the reader that ~SETTABLE is a subset of ~CLEARABLE, and they might
> think "well what about the settable flags we just cleared?"
> 
> To be honest I wouldn't mind leaving the code as-is, since it more
> clearly describes what happens, and presumably the compiler will be
> smart enough to optimize this anyway. But if you have other ideas on
> how to remove this line and make things easier to understand, let me
> know.
> 
Thanks for your reply. From code readability, I agree with you and keep 
this code here is better. So ignore this patch.

Best Regards
Yang Xu
> Best,
> Martijn
> 
> On Sat, Aug 1, 2020 at 5:04 AM Yang Xu <xuyang2018.jy@cn.fujitsu.com> wrote:
>>
>> Hi
>> Ping.
>>
>>> Since ~LOOP_SET_STATUS_SETTABLE_FLAG is always a subset of ~LOOP_SET_STATUS_CLEARABLE_FLAGS
>>> ,remove this redundant flags operation.
>>>
>>> Cc: Martijn Coenen <maco@android.com>
>>> Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
>>> ---
>>>    drivers/block/loop.c | 2 --
>>>    1 file changed, 2 deletions(-)
>>>
>>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
>>> index c33bbbf..2a61079 100644
>>> --- a/drivers/block/loop.c
>>> +++ b/drivers/block/loop.c
>>> @@ -1391,8 +1391,6 @@ static int loop_clr_fd(struct loop_device *lo)
>>>
>>>        /* Mask out flags that can't be set using LOOP_SET_STATUS. */
>>>        lo->lo_flags &= LOOP_SET_STATUS_SETTABLE_FLAGS;
>>> -     /* For those flags, use the previous values instead */
>>> -     lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_SETTABLE_FLAGS;
>>>        /* For flags that can't be cleared, use previous values too */
>>>        lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_CLEARABLE_FLAGS;
>>>
>>>
>>
>>
> 
>