linux-kernel - Re: [PATCH 1/2] open: add close

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Message-ID: <CAHrFyr4NV_5Z7TRSXTaurd4KCTLiHqKb47dN=bdY46HiL9ZY3Q@mail.gmail.com>
Date:   Wed, 22 May 2019 10:12:11 +0200
From:   Christian Brauner <christian@...uner.io>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     David Howells <dhowells@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>,
        Florian Weimer <fweimer@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>, Shuah Khan <shuah@...nel.org>,
        Todd Kjos <tkjos@...roid.com>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        alpha <linux-alpha@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-ia64@...r.kernel.org,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        linux-mips@...r.kernel.org,
        Parisc List <linux-parisc@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Linux-sh list <linux-sh@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linux-xtensa@...ux-xtensa.org,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH 1/2] open: add close_range()

On Tue, May 21, 2019 at 10:23 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Tue, May 21, 2019 at 9:41 AM Christian Brauner <christian@...uner.io> wrote:
> >
> > Yeah, you mentioned this before. I do like being able to specify an
> > upper bound to have the ability to place fds strategically after said
> > upper bound.
>
> I suspect that's the case.
>
> And if somebody really wants to just close everything and uses a large
> upper bound, we can - if we really want to - just compare the upper
> bound to the file table size, and do an optimized case for that. We do
> that upper bound comparison anyway to limit the size of the walk, so
> *if* it's a big deal, that case could then do the whole "shrink
> fdtable" case too.

Makes sense.

>
> But I don't believe it's worth optimizing for unless somebody really
> has a load where that is shown to be a big deal.   Just do the silly
> and simple loop, and add a cond_resched() in the loop, like
> close_files() does for the "we have a _lot_ of files open" case.

Ok. I will resend a v1 later with the cond_resched() logic you and Al
suggested added.

Thanks!
Christian