linux-kernel - Re: [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct

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Message-ID: <3122384.1628777791@warthog.procyon.org.uk>
Date:   Thu, 12 Aug 2021 15:16:31 +0100
From:   David Howells <dhowells@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     dhowells@...hat.com, trond.myklebust@...marydata.com,
        darrick.wong@...cle.com, hch@....de, jlayton@...nel.org,
        sfrench@...ba.org, torvalds@...ux-foundation.org,
        linux-nfs@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct_IO() not ->readpage()

Matthew Wilcox <willy@...radead.org> wrote:

> This is a read, not a write ... but we don't care about ki_pos being
> updated, so that store can be conditioned on IOCB_SWAP being clear.
> Or instead of storing directly to ki_pos, we take a pointer to ki_pos
> and then redirect that pointer somewhere harmless.

But see also ext4_dio_read_iter(), for example.  That touches ki_filp after
starting the op.

David