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

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Message-ID: <20200907064758.GA19384@lst.de>
Date:   Mon, 7 Sep 2020 08:47:58 +0200
From:   Christoph Hellwig <hch@....de>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        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@...ck.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org
Subject: Re: [PATCH 2/2] xfs: don't update mtime on COW faults

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

This function does not look xfs specific at all.  Why isn't it it in
fs.h?  While we're at it the name sounds rather generic, and there are
no good comments.

Maybe we just need to split FAULT_FLAG_WRITE into two and check those
instead of such crazy workarounds?