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From: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
To: Martijn Coenen <maco@android.com>
Cc: linux-block <linux-block@vger.kernel.org>
Subject: Re: [PATCH] loop: Remove redundant status flag operation
Date: Thu, 6 Aug 2020 16:03:17 +0800
Message-ID: <933aa74f-4ee8-5e9c-4176-1a888ed7e035@cn.fujitsu.com> (raw)
In-Reply-To: <CAB0TPYEvfCSCNyBZTB5hMF2AfcV5jLMr0jyxmpjfeyvSwYcwUA@mail.gmail.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;
>>>
>>>
>>
>>
> 
> 



      reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-12  2:43 Yang Xu
2020-08-01  3:04 ` Yang Xu
2020-08-06  7:45   ` Martijn Coenen
2020-08-06  8:03     ` Yang Xu [this message]

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