linux-kernel - Re: How does ftruncate() interact with DIO read?

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Date:   Fri, 3 Feb 2023 17:31:07 +0100
From:   Christoph Hellwig <hch@....de>
To:     David Howells <dhowells@...hat.com>
Cc:     Christoph Hellwig <hch@....de>, John Hubbard <jhubbard@...dia.com>,
        David Hildenbrand <david@...hat.com>,
        syzbot <syzbot+a440341a59e3b7142895@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: How does ftruncate() interact with DIO read?

On Fri, Feb 03, 2023 at 04:27:10PM +0000, David Howells wrote:
> Hi Christoph,
> 
> What does ftruncate() do if there's a conflicting DIO read happening on the
> same file?  Does it cancel the bio?

There is no way to cancel a bio.  ->setattr is supposed to call
inode_dio_wait to wait for pending I/O, although some file systems
like btrfs have their own hand crafted and more complicated version
of that.