linux-kernel - Re: [PATCH v5 6/6] mm,thp: avoid writes to file with THP in pagecache

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Message-ID: <7bbcb43070c5b07e5862e2dbdc7155efcae3eb4a.camel@fb.com>
Date:   Fri, 21 Jun 2019 00:52:48 +0000
From:   Rik van Riel <riel@...com>
To:     Song Liu <songliubraving@...com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "matthew.wilcox@...cle.com" <matthew.wilcox@...cle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Kernel Team" <Kernel-team@...com>,
        "william.kucharski@...cle.com" <william.kucharski@...cle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v5 6/6] mm,thp: avoid writes to file with THP in pagecache

On Thu, 2019-06-20 at 13:53 -0700, Song Liu wrote:
> In previous patch, an application could put part of its text section
> in
> THP via madvise(). These THPs will be protected from writes when the
> application is still running (TXTBSY). However, after the application
> exits, the file is available for writes.
> 
> This patch avoids writes to file THP by dropping page cache for the
> file
> when the file is open for write. A new counter nr_thps is added to
> struct
> address_space. In do_last(), if the file is open for write and
> nr_thps
> is non-zero, we drop page cache for the whole file.
> 
> Signed-off-by: Song Liu <songliubraving@...com>

Acked-by: Rik van Riel <riel@...riel.com>


The comment for release_file_thp() is a little implementation
specific, which is normally a bad thing (for code we expect
to stick around for years), but probably the right thing for
code that is just a step in the direction we want to go.

Thank you for reworking these patches so quickly.