Re: multipath: I/O hanging forever

[Ming Lei]

On Fri, 11 Mar 2016 15:24:33 -0700
Andrea Righi <righi.andrea@xxxxxxxxx> wrote:

> On Sat, Mar 05, 2016 at 08:31:03PM -0900, Kent Overstreet wrote:
> > On Fri, Mar 04, 2016 at 10:30:44AM -0700, Andrea Righi wrote:
> > > On Sun, Feb 28, 2016 at 08:46:16PM -0700, Andrea Righi wrote:
> > > > On Sun, Feb 28, 2016 at 06:53:33PM -0700, Andrea Righi wrote:
> > > > ... 
> > > > > I'm using 4.5.0-rc5+, from Linus' git. I'll try to do a git bisect
> > > > > later, I'm pretty sure this problem has been introduced recently (i.e.,
> > > > > I've never seen this issue with 4.1.x).
> > > > 
> > > > I confirm, just tested kernel 4.1 and this problem doesn't happen.
> > > 
> > > Alright, I had some spare time to bisect this problem and I found that
> > > the commit that introduced this issue is c66a14d.
> > > 
> > > So, I tried to revert the commit (with some changes to fix conflicts and
> > > ABI changes) and now multipath seems to work fine for me (no hung task).
> > 
> > Is it hanging on first IO, first large IO, or just randomly?
> 
> It's always the very first O_DIRECT I/O, in general the task gets stuck
> in do_blockdev_direct_IO().

I can reproduce the issue too, and looks it is a MD issue instead of block.
Andrea, could you try the following patch to see if it can fix your issue?

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