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Date:   Fri, 13 Aug 2021 09:14:15 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     David Howells <dhowells@redhat.com>
Cc:     willy@infradead.org, trond.myklebust@primarydata.com,
        darrick.wong@oracle.com, hch@lst.de, viro@zeniv.linux.org.uk,
        jlayton@kernel.org, sfrench@samba.org,
        torvalds@linux-foundation.org, linux-nfs@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 5/5] mm: Remove swap BIO paths and only use DIO
 paths [BROKEN]
Message-ID: <20210813071415.GD26339@lst.de>
References: <162879971699.3306668.8977537647318498651.stgit@warthog.procyon.org.uk> <162879976139.3306668.12495248062404308890.stgit@warthog.procyon.org.uk>
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On Thu, Aug 12, 2021 at 09:22:41PM +0100, David Howells wrote:
> [!] NOTE: This doesn't work and might damage your disk's contents.
> 
> Delete the BIO-generating swap read/write paths and always use
> ->direct_IO().  This puts the mapping layer in the filesystem.
> 
> This doesn't work - probably due to ki_pos being set to
> page_file_offset(page) which then gets remapped.

Also because most common block file systems do not actually implement
a ->direct_IO that does anything (noop_direct_IO).