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From: Suren Baghdasaryan <surenb@google.com>
To: David Hildenbrand <david@redhat.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 13:19:35 -0700	[thread overview]
Message-ID: <CAJuCfpHtRzCNH6Cspu8ngjw+WLvZTMsVbmBu_F-z8YY_n=RbvA@mail.gmail.com> (raw)
In-Reply-To: <0ee6775b-589c-3243-1c01-aafad5eecb73@redhat.com>

On Wed, Jul 21, 2021 at 9:13 AM David Hildenbrand <david@redhat.com> wrote:
>
> 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.

Andrew, others? Should I follow this path instead?

>
> --
> Thanks,
>
> David / dhildenb
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>

  reply	other threads:[~2021-07-21 20:19 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
2021-07-21 20:19           ` Suren Baghdasaryan [this message]
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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