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Date:   Mon, 27 Feb 2023 05:36:04 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Jan Kara <jack@suse.cz>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Dave Chinner <david@fromorbit.com>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-mm@kvack.org, John Hubbard <jhubbard@nvidia.com>,
        David Howells <dhowells@redhat.com>,
        David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH 4/5] block: Add support for bouncing pinned pages
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On Mon, Feb 27, 2023 at 12:39:26PM +0100, Jan Kara wrote:
> Do you mean to copy these pages on fsync(2) to newly allocated buffer and
> then submit it via direct IO? That looks sensible to me. We could then make
> writeback path just completely ignore these long term pinned pages and just
> add this copying logic into filemap_fdatawrite() or something like that.

I don't think we'd even have to copy them on fsync.  Just do an in-kernel
ITER_BVEC direct I/O on them.  The only hard part would be to come up
with a way to skip the pagecache invalidation and writeout for these
I/Os.