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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 9 Jan 2019 17:18:21 -0800
Message-ID: <CAHk-=wg1jSQ-gq-M3+HeTBbDs1VCjyiwF4gqnnBhHeWizyrigg@mail.gmail.com>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged
To:     Dave Chinner <david@fromorbit.com>
Cc:     Jiri Kosina <jikos@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Michal Hocko <mhocko@suse.com>, Linux-MM <linux-mm@kvack.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>
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On Wed, Jan 9, 2019 at 4:44 PM Dave Chinner <david@fromorbit.com> wrote:
>
> I wouldn't look at ext4 as an example of a reliable, problem free
> direct IO implementation because, historically speaking, it's been a
> series of nasty hacks (*cough* mount -o dioread_nolock *cough*) and
> been far worse than XFS from data integrity, performance and
> reliability perspectives.

That's some big words from somebody who just admitted to much worse hacks.

Seriously. XFS is buggy in this regard, ext4 apparently isn't.

Thinking that it's better to just invalidate the cache  for direct IO
reads is all kinds of odd.

                Linus