linux-ext4 - Re: [PATCH 1/8] mm/fs: don't allow writes to immutable files

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Date:   Mon, 10 Jun 2019 09:14:17 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/8] mm/fs: don't allow writes to immutable files

On Sun, Jun 09, 2019 at 09:41:44PM -0700, Darrick J. Wong wrote:
> On Sun, Jun 09, 2019 at 09:51:45PM -0400, Theodore Ts'o wrote:
> > On Wed, Apr 17, 2019 at 12:04:33PM -0700, Darrick J. Wong wrote:
>
> > Shouldn't this check be moved before the modification of vmf->flags?
> > It looks like do_page_mkwrite() isn't supposed to be returning with
> > vmf->flags modified, lest "the caller gets surprised".
> 
> Yeah, I think that was a merge error during a rebase... :(
> 
> Er ... if you're still planning to take this patch through your tree,
> can you move it to above the "vmf->flags = FAULT_FLAG_WRITE..." ?

I was planning on only taking 8/8 through the ext4 tree.  I also added
a patch which filtered writes, truncates, and page_mkwrites (but not
mmap) for immutable files at the ext4 level.

I *could* take this patch through the mm/fs tree, but I wasn't sure
what your plans were for the rest of the patch series, and it seemed
like it hadn't gotten much review/attention from other fs or mm folks
(well, I guess Brian Foster weighed in).

What do you think?

						- Ted