[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <948E780F-14EB-4E38-9BAC-A5410F339441@dilger.ca>
Date: Thu, 9 Oct 2014 14:50:34 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Dmitry Monakhov <dmonakhov@...nvz.org>
Cc: linux-ext4@...r.kernel.org, sasha.levin@...cle.com
Subject: Re: [PATCH] ext4: fix race between write and fcntl(F_SETFL)
On Oct 9, 2014, at 5:14 AM, Dmitry Monakhov <dmonakhov@...nvz.org> wrote:
> O_DIRECT flags can be toggeled via fcntl(F_SETFL).
> But this value checked twice inside ext4_file_write_iter() and __generic_file_write()
> which result in BUG_ON (see typical stack trace below)
> In order to fix this we have to use our own copy of __generic_file_write
> and pass o_direct status explicitly.
This seems like a generic problem that would be better served by fixing
the core code instead of making a private copy of such a large function
for ext4. I expect other filesystems might have similar issues if the
O_DIRECT state is changed in the middle of IO?
One option is to flush pending IO on the file if the O_DIRECT flag is
changed in setfl(). This is a bit heavyweight but I can't imagine any
sane app that is changing the O_DIRECT state on a file repeatedly.
Cheers, Andreas
Download attachment "signature.asc" of type "application/pgp-signature" (834 bytes)
Powered by blists - more mailing lists