lkml.org 
[lkml]   [2013]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: next-20130117 - kernel BUG with aio
On Thu 24-01-13 14:13:52, Kent Overstreet wrote:
> On Thu, Jan 24, 2013 at 01:27:59PM -0800, Andrew Morton wrote:
> > Please also take a look at Jan's recent
> > http://www.spinics.net/lists/linux-fsdevel/msg61738.html and have a
> > think about how this plays with your patchset.
>
> I can't think of any possible interactions - none of my aio stuff messes
> with the way the fput() happens; the aio code does call fput() when the
> kiocb is freed and my patches do touch _that_ code but none of the
> behaviour there changes.
>
> Might be worth documenting this though, I can't think of any reason it'd
> be obvious looking at the aio code that the fput() has to happen after
> aio_complete(). As with the bugs I just sent you patches for it's not
> terribly clear who owns what in the kiocb when.
>
> Reading those patches though - the main change is to call
> inode_dio_done() before calling aio_complete(). All inode_dio_done()
> does though is issue a wakeup - to whatever called inode_dio_wait().
inode_dio_done() does a decrement and wakeup.

> That means whatever called inode_dio_wait() needs its own ref on the
> inode, and from a cursory glance at the code it is _not_ at all clear to
> me that's the case - if inode_dio_wait() is merely finishing things for
> that specific IO that need to be done in process context, I can easily
> imagine it not being the case.
>
> Assuming whatever does call inode_dio_wait() does have its own ref,
> there was only a real use after free when nothing was waiting on the
> inode.
Well, but there doesn't have to be any waiter... If there is, it had
better have it's own ref, that's for sure.

> Similarly for the ext4 code to write unwritten extents - and having seen
> and helped chase a bug in that code before, that code _definitely_ needs
> auditing.
Agreed. That code is a mess. I'm cleaning up some of it but it's not
easy.

Honza

--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


\
 
 \ /
  Last update: 2013-01-29 15:21    [W:0.176 / U:4.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site