Re: [PATCH v2] fs: Fix page cache inconsistency when mixing buffered and AIO DIO

From: Lukas Czerner <lczerner@redhat.com>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Jan Kara <jack@suse.cz>,
	linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk
Subject: Re: [PATCH v2] fs: Fix page cache inconsistency when mixing buffered and AIO DIO
Date: Tue, 18 Jul 2017 09:39:35 +0200	[thread overview]
Message-ID: <20170718073935.ffqoq5lc6vj4lhvx@localhost.localdomain> (raw)
In-Reply-To: <x49o9sjrs2q.fsf@segfault.boston.devel.redhat.com>

On Mon, Jul 17, 2017 at 11:39:09AM -0400, Jeff Moyer wrote:
> Lukas Czerner <lczerner@redhat.com> writes:
> 
> > About the error case, is it not possible that some data has already been
> > writtent to the disk despite the error ?
> 
> Yes, it's possible.  However, that data is in an inconsistent state, so
> it shouldn't be read, anyway.

I think it can be read if we wrote into already allocated space.

> 
> Now, in the non-async path, we do the invalidation unconditionally, so I
> could go either way on this.  I don't think it's going to matter for
> performance or data integrity.

That's part of the reason why I did it unconditionaly as well, however
Jan is right that ret would be negative. The way to fix it would differ
depending on whether I am right about reading partially written data
from AIO that failed. We still want to invalidate in that case.

-Lukas

> 
> Cheers,
> Jeff