All of lore.kernel.org
 help / color / mirror / Atom feed
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Hugh Dickins <hughd@google.com>, Christoph Lameter <cl@linux.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH 1/4] hugetlb, rmap: always use anon_vma root pointer
Date: Fri, 10 Sep 2010 15:07:08 -0700	[thread overview]
Message-ID: <AANLkTinFqM4BSD0jkrqkrNxg-o+3eC6QQ6zq8jKdaLJx@mail.gmail.com> (raw)
In-Reply-To: <20100910235022.74ec04de@basil.nowhere.org>

On Fri, Sep 10, 2010 at 2:50 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> Btw, why isn't the code in __page_set_anon_rmap() also doing this
>> cleaner version (ie a single "if (PageAnon(page)) return;" up front)?
>
> Perhaps I misunderstand the question, but __page_set_anon_rmap
> should handle Anon pages, shouldn't it?

I'm talking about this:

    if (!exclusive) {
        if (PageAnon(page))
            return;
        anon_vma = anon_vma->root;
    } else {
        .. big bad comment ...
        if (PageAnon(page))
            return;
    }

where both sides of the if-statement start off doing the same thing.

It would be much cleaner to just do

    ... big _comprehensible_ comment ...
    if (PageAnon(page))
        return;

    if (!exclusive)
        anon_vma = anon_vma->root;

which avoids that silly else that just does something that we always do.

The reason I reacted is that Naoya-san's patch did that cleaner
version for the hugetlb case. So when I compared it to the non-hugetlb
case I just went "Ewww..."

                             Linus

WARNING: multiple messages have this Message-ID (diff)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Hugh Dickins <hughd@google.com>, Christoph Lameter <cl@linux.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH 1/4] hugetlb, rmap: always use anon_vma root pointer
Date: Fri, 10 Sep 2010 15:07:08 -0700	[thread overview]
Message-ID: <AANLkTinFqM4BSD0jkrqkrNxg-o+3eC6QQ6zq8jKdaLJx@mail.gmail.com> (raw)
In-Reply-To: <20100910235022.74ec04de@basil.nowhere.org>

On Fri, Sep 10, 2010 at 2:50 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> Btw, why isn't the code in __page_set_anon_rmap() also doing this
>> cleaner version (ie a single "if (PageAnon(page)) return;" up front)?
>
> Perhaps I misunderstand the question, but __page_set_anon_rmap
> should handle Anon pages, shouldn't it?

I'm talking about this:

    if (!exclusive) {
        if (PageAnon(page))
            return;
        anon_vma = anon_vma->root;
    } else {
        .. big bad comment ...
        if (PageAnon(page))
            return;
    }

where both sides of the if-statement start off doing the same thing.

It would be much cleaner to just do

    ... big _comprehensible_ comment ...
    if (PageAnon(page))
        return;

    if (!exclusive)
        anon_vma = anon_vma->root;

which avoids that silly else that just does something that we always do.

The reason I reacted is that Naoya-san's patch did that cleaner
version for the hugetlb case. So when I compared it to the non-hugetlb
case I just went "Ewww..."

                             Linus

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  reply	other threads:[~2010-09-10 22:07 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-10  4:23 [PATCH 0/4] hugetlb, rmap: fixes and cleanups Naoya Horiguchi
2010-09-10  4:23 ` Naoya Horiguchi
2010-09-10  4:23 ` [PATCH 1/4] hugetlb, rmap: always use anon_vma root pointer Naoya Horiguchi
2010-09-10  4:23   ` Naoya Horiguchi
2010-09-10 14:37   ` Andrea Arcangeli
2010-09-10 14:37     ` Andrea Arcangeli
2010-09-10 14:40   ` Rik van Riel
2010-09-10 14:40     ` Rik van Riel
2010-09-10 17:19   ` Linus Torvalds
2010-09-10 17:19     ` Linus Torvalds
2010-09-10 21:50     ` Andi Kleen
2010-09-10 21:50       ` Andi Kleen
2010-09-10 22:07       ` Linus Torvalds [this message]
2010-09-10 22:07         ` Linus Torvalds
2010-09-11  2:09       ` Rik van Riel
2010-09-11  2:09         ` Rik van Riel
2010-09-10  4:23 ` [PATCH 2/4] hugetlb, rmap: use hugepage_add_new_anon_rmap() in hugetlb_cow() Naoya Horiguchi
2010-09-10  4:23   ` Naoya Horiguchi
2010-09-10 14:39   ` Andrea Arcangeli
2010-09-10 14:39     ` Andrea Arcangeli
2010-09-10 14:40   ` Rik van Riel
2010-09-10 14:40     ` Rik van Riel
2010-09-10  4:23 ` [PATCH 3/4] hugetlb, rmap: fix confusing page locking " Naoya Horiguchi
2010-09-10  4:23   ` Naoya Horiguchi
2010-09-10 14:41   ` Rik van Riel
2010-09-10 14:41     ` Rik van Riel
2010-09-10 17:15   ` Linus Torvalds
2010-09-10 17:15     ` Linus Torvalds
2010-09-23 23:50     ` Naoya Horiguchi
2010-09-23 23:50       ` Naoya Horiguchi
2010-09-10  4:23 ` [PATCH 4/4] hugetlb, rmap: add BUG_ON(!PageLocked) in hugetlb_add_anon_rmap() Naoya Horiguchi
2010-09-10  4:23   ` Naoya Horiguchi
2010-09-10 14:42   ` Rik van Riel
2010-09-10 14:42     ` Rik van Riel
2010-09-10 14:44   ` Andrea Arcangeli
2010-09-10 14:44     ` Andrea Arcangeli
2010-09-10  9:04 ` [PATCH 0/4] hugetlb, rmap: fixes and cleanups Andi Kleen
2010-09-10  9:04   ` Andi Kleen
2010-09-10 11:47   ` Naoya Horiguchi
2010-09-10 11:47     ` Naoya Horiguchi
2010-09-10 14:30     ` Andi Kleen
2010-09-10 14:30       ` Andi Kleen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=AANLkTinFqM4BSD0jkrqkrNxg-o+3eC6QQ6zq8jKdaLJx@mail.gmail.com \
    --to=torvalds@linux-foundation.org \
    --cc=aarcange@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=andi@firstfloor.org \
    --cc=cl@linux.com \
    --cc=hughd@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=n-horiguchi@ah.jp.nec.com \
    --cc=peterz@infradead.org \
    --cc=riel@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.