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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <0b154b9b-728f-7d57-d4c5-ec25fc9dfdf3@toxicpanda.com>
References: <0b154b9b-728f-7d57-d4c5-ec25fc9dfdf3@toxicpanda.com>
To:     Josef Bacik <josef@toxicpanda.com>
Cc:     dhowells@redhat.com,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Eric Sandeen <sandeen@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        David Sterba <dsterba@suse.com>
Subject: Re: Inverted mount options completely broken (iversion,relatime)
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Date:   Wed, 29 Jul 2020 21:36:56 +0100
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Josef Bacik <josef@toxicpanda.com> wrote:

> So my question is, what do we do here?

Hmmm...  As the code stands, MS_RDONLY, MS_SYNCHRONOUS, MS_MANDLOCK,
MS_I_VERSION and MS_LAZYTIME should all be masked off before the new flags are
set if called from mount(2) rather than fsconfig(2).

do_remount() gives MS_RMT_MASK to fs_context_for_reconfigure() to load into
fc->sb_flags_mask, which should achieve the desired effect in
reconfigure_super() on this line:

	WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
				 (fc->sb_flags & fc->sb_flags_mask)));

David