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From: David Hildenbrand <david@redhat.com>
To: Suren Baghdasaryan <surenb@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@kernel.org>, Michal Hocko <mhocko@suse.com>,
	David Rientjes <rientjes@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>,
	Minchan Kim <minchan@kernel.org>,
	Christian Brauner <christian@brauner.io>,
	Christoph Hellwig <hch@infradead.org>,
	Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
	Shakeel Butt <shakeelb@google.com>,
	Andy Lutomirski <luto@kernel.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Florian Weimer <fweimer@redhat.com>,
	Jan Engelhardt <jengelh@inai.de>,
	Tim Murray <timmurray@google.com>,
	Linux API <linux-api@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-team <kernel-team@android.com>
Subject: Re: [PATCH v2 1/3] mm, oom: move task_will_free_mem up in the file to be used in process_mrelease
Date: Wed, 21 Jul 2021 18:12:56 +0200	[thread overview]
Message-ID: <0ee6775b-589c-3243-1c01-aafad5eecb73@redhat.com> (raw)
In-Reply-To: <CAJuCfpEB994Xj3FcmzyH1p3yOdLVf6EwZaGaRj7NJi_c9hbsRQ@mail.gmail.com>

On 21.07.21 17:33, Suren Baghdasaryan wrote:
> On Wed, Jul 21, 2021 at 12:30 AM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 21.07.21 01:07, Andrew Morton wrote:
>>> On Tue, 20 Jul 2021 14:43:52 +0200 David Hildenbrand <david@redhat.com> wrote:
>>>
>>>> On 18.07.21 23:41, Suren Baghdasaryan wrote:
>>>>> process_mrelease needs to be added in the CONFIG_MMU-dependent block which
>>>>> comes before __task_will_free_mem and task_will_free_mem. Move these
>>>>> functions before this block so that new process_mrelease syscall can use
>>>>> them.
>>>>>
>>>>> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>>>>> ---
>>>>> changes in v2:
>>>>> - Fixed build error when CONFIG_MMU=n, reported by kernel test robot. This
>>>>> required moving task_will_free_mem implemented in the first patch
>>>>> - Renamed process_reap to process_mrelease, per majority of votes
>>>>> - Replaced "dying process" with "process which was sent a SIGKILL signal" in
>>>>> the manual page text, per Florian Weimer
>>>>> - Added ERRORS section in the manual page text
>>>>> - Resolved conflicts in syscall numbers caused by the new memfd_secret syscall
>>>>> - Separated boilerplate code wiring-up the new syscall into a separate patch
>>>>> to facilitate the review process
>>>>>
>>>>>     mm/oom_kill.c | 150 +++++++++++++++++++++++++-------------------------
>>>>>     1 file changed, 75 insertions(+), 75 deletions(-)
>>>>
>>>> TBH, I really dislike this move as it makes git blame a lot harder with
>>>> any real benefit.
>>>>
>>>> Can't you just use prototypes to avoid the move for now in patch #2?
>>>>
>>>> static bool task_will_free_mem(struct task_struct *task);
>>>
>>> This change makes the code better - it's silly to be adding forward
>>> declarations just because the functions are in the wrong place.
>>
>> I'd really love to learn what "better" here means and if it's rather
>> subjective. When it comes to navigating the code, we do have established
>> tools for that (ctags), and personally I couldn't care less where
>> exactly in a file the code is located.
>>
>> Sure, ending up with a forward-declaration for every function might not
>> be what we want ;)
>>
>>>
>>> If that messes up git-blame then let's come up with better tooling
>>> rather than suffering poorer kernel code because the tools aren't doing
>>> what we want of them.  Surely?
>>
>> I don't agree that what we get is "poorer kernel code" in this very
>> instance; I can understand that we avoid forward-declarations when
>> moving smallish functions. But moving two functions with 75 LOC is a bit
>> too much for my taste at least -- speaking as someone who cares about
>> easy backports and git-blame.
> 
> There is a third alternative here to have process_mrelease() at the
> end of the file with its own #ifdef CONFIG_MMU block, maybe even
> embedded in the function like this:
> 
>   int process_mrelease(int pidfd, unsigned int flags)
> {
> #ifdef CONFIG_MMU
>          ...
> #else
>          return ENOSYS;
> #endif
> }
> 
> This would not require moving other functions.
> Would that be better than the current approach or the forward declaration?

IMHO that could be an easy, possible alternative.

-- 
Thanks,

David / dhildenb


  reply	other threads:[~2021-07-21 16:13 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-18 21:41 Suren Baghdasaryan
2021-07-18 21:41 ` [PATCH v2 2/3] mm: introduce process_mrelease system call Suren Baghdasaryan
2021-07-21  8:02   ` David Hildenbrand
2021-07-21 15:43     ` Suren Baghdasaryan
2021-07-21 22:59       ` Suren Baghdasaryan
2021-07-22  7:45         ` David Hildenbrand
2021-07-18 21:41 ` [PATCH v2 3/3] mm: wire up syscall process_mrelease Suren Baghdasaryan
2021-07-20 12:43 ` [PATCH v2 1/3] mm, oom: move task_will_free_mem up in the file to be used in process_mrelease David Hildenbrand
2021-07-20 16:18   ` Suren Baghdasaryan
2021-07-20 23:07   ` Andrew Morton
2021-07-21  7:30     ` David Hildenbrand
2021-07-21 15:33       ` Suren Baghdasaryan
2021-07-21 16:12         ` David Hildenbrand [this message]
2021-07-21 20:19           ` Suren Baghdasaryan
2021-07-21 20:50             ` Andrew Morton
2021-07-21 20:59               ` Suren Baghdasaryan
2021-07-23  1:15                 ` Suren Baghdasaryan

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