From: Colin Walters <walters@verbum.org>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Jan Kara <jack@suse.cz>,
linux-nvdimm@lists.01.org, Dave Chinner <david@fromorbit.com>,
linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
linux-xfs@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 1/3] fs, xfs: introduce S_IOMAP_IMMUTABLE
Date: Mon, 31 Jul 2017 22:15:12 -0400 [thread overview]
Message-ID: <1501553712.1055225.1059044352.109C04CB@webmail.messagingengine.com> (raw)
In-Reply-To: <20170731182352.GE4477@magnolia>
On Mon, Jul 31, 2017, at 02:23 PM, Darrick J. Wong wrote:
> I don't think F_SEAL_{SHRINK,GROW} prevents reflinking or CoW of file data,
> which are two things that cannot happen under S_IOMAP_IMMUTABLE that
> aren't size changes. From the implementation it looks like shrink and
> grow are only supposed to disallow changes to i_size, not i_blocks (or
> the file block map).
True.
> Then again, I suppose F_SEAL_* only work on shmem, so maybe it simply
> isn't defined for any other filesystem...? e.g. it doesn't prohibit
> reflink, but the only fs implementing seals doesn't support reflink.
>
> <shrug>
>
> Seals cannot be removed, which is too strict for the S_IOMAP_IMMUTABLE
> user cases being presented.
To be clear, the set of use cases is swap files and DAX, right? Or is there anything else?
I can't imagine why anyone would want to turn a swap file back into a regular file.
I haven't fully followed DAX, but I'd take your word for it if people want to
be able to remove the flag after.
Anyways, I think your broader point is right; the use cases are different enough
that it doesn't make sense to try to add S_CONTENT_IMMUTABLE (or however
one decides to call it) at the same time.
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next prev parent reply other threads:[~2017-08-01 2:13 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-29 19:43 [PATCH 0/3] fs, xfs: block map immutable files for dax, dma-to-storage, and swap Dan Williams
2017-07-29 19:43 ` [PATCH 1/3] fs, xfs: introduce S_IOMAP_IMMUTABLE Dan Williams
2017-07-31 16:02 ` Colin Walters
2017-07-31 16:29 ` Dan Williams
2017-07-31 16:32 ` Colin Walters
2017-07-31 17:42 ` Colin Walters
2017-07-31 18:23 ` Darrick J. Wong
2017-08-01 2:15 ` Colin Walters [this message]
2017-08-01 2:42 ` Dave Chinner
2017-08-05 9:45 ` Christoph Hellwig
2017-07-31 16:46 ` Darrick J. Wong
2017-07-31 17:32 ` Dan Williams
2017-07-29 19:43 ` [PATCH 2/3] fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP Dan Williams
2017-07-31 17:09 ` Darrick J. Wong
2017-07-31 18:25 ` Dan Williams
2017-08-01 0:30 ` Dave Chinner
2017-07-29 19:43 ` [PATCH 3/3] xfs: persist S_IOMAP_IMMUTABLE in di_flags2 Dan Williams
2017-07-31 17:15 ` Darrick J. Wong
2017-08-01 0:42 ` Dave Chinner
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