linux-ext4 - Re: [PATCH 2/2] xfs: don't update mtime on COW faults

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Message-ID: <CAHk-=wgNoq2kh_xYKtTX38GJdEC_iAvoeFU9gpj6kFVaiA0o=A@mail.gmail.com>
Date:   Sat, 5 Sep 2020 10:03:20 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Jan Kara <jack@...e.cz>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Dave Chinner <dchinner@...hat.com>,
        Jann Horn <jannh@...gle.com>, Christoph Hellwig <hch@....de>,
        Oleg Nesterov <oleg@...hat.com>,
        Kirill Shutemov <kirill@...temov.name>,
        "Theodore Ts'o" <tytso@....edu>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>
Subject: Re: [PATCH 2/2] xfs: don't update mtime on COW faults

On Sat, Sep 5, 2020 at 9:47 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> So your patch is obviously correct, [..]

Oh, and I had a xfs pull request in my inbox already, so rather than
expect Darrick to do another one just for this and have Jan do one for
ext2, I just applied these two directly as "ObviouslyCorrect(tm)".

I added the "inline" as suggested by Darrick, and I also added
parenthesis around the bit tests.

Yes, I know the C precedence rules, but I just personally find the
code easier to read if I don't even have to think about it and the
different subexpressions of a logical operation are just visually very
clear. And as I was editing the patch anyway...

So that xfs helper function now looks like this

+static inline bool
+xfs_is_write_fault(
+       struct vm_fault         *vmf)
+{
+       return (vmf->flags & FAULT_FLAG_WRITE) &&
+              (vmf->vma->vm_flags & VM_SHARED);
+}

instead.

            Linus