Re: BTRFS hang with 3.16-rc5 (and also with 3.16-rc4)

[Liu Bo <bo.li.liu@oracle.com>]

On Fri, Jul 25, 2014 at 01:37:10PM +0200, Torbjørn wrote:
> On 25. juli 2014 13:09, Torbjørn wrote:
> >On 25. juli 2014 12:22, Torbjørn wrote:
> >>On 25. juli 2014 11:28, Liu Bo wrote:
> >>>Hi Torbjørn,
> >>>
> >>>On Fri, Jul 25, 2014 at 06:51:44AM +0200, Torbjørn wrote:
> >>>>On 07/24/2014 04:58 PM, Chris Mason wrote:
> >>>>><snip>
> >>>>>Liu Bo has a promising patch:
> >>>>>
> >>>>>https://patchwork.kernel.org/patch/4618421/
> >>>>>
> >>>>>Please give it a shot.  There's a second deadlock reading
> >>>>>the free space
> >>>>>cache, I'm still working on that one too.
> >>>>>
> >>>>>-chris
> >>>>I (as expected, my hang was with free space cache) still get hangs
> >>>>with this applied on top of 3.16-rc6.
> >>>>Looking forward to the free space cache patch.
> >>>>
> >>>>I have not been able to trigger the same hang as I had with 3.15 on
> >>>>any of the 3.16-rc6 kernels so far.
> >>>Seems that you can run into the hang quite stably, I have a
> >>>stupid debugging
> >>>patch here with adding a WARN_ON() to
> >>>__load_free_space_inode(), would you
> >>>please give it a shot and show us the output of dmesg?
> >>>
> >>>(This may make 'dmesg' a mess, but it will show who the hell
> >>>holds the free
> >>>space inode's page just at the time before hang)
> >>>
> >>>thanks,
> >>>-liubo
> >>>
> >>>
> >>>diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> >>>index 2b0a627..e364888 100644
> >>>--- a/fs/btrfs/free-space-cache.c
> >>>+++ b/fs/btrfs/free-space-cache.c
> >>>@@ -350,6 +350,8 @@ static int io_ctl_prepare_pages(struct
> >>>io_ctl *io_ctl,
> >>>struct inode *inode,
> >>>      gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
> >>>      int i;
> >>>  +    WARN_ON(1);
> >>>+
> >>>      for (i = 0; i < io_ctl->num_pages; i++) {
> >>>          page = find_or_create_page(inode->i_mapping, i, mask);
> >>>          if (!page) {
> >>
> >>That patch did not apply cleanly on top of current linus master.
> >>Not sure what branch you are at, so I added that WARN_ON(1);
> >>manually in free-space-cache.c.
> >>I reverted all the other patches before manually applying this one.
> >>If you need me to test from some other branch or with some other
> >>patch included, please let me know.
> >>
> >>I'm doing a build now. Will run my rsync job and report back.
> >>
> >>Thanks.
> >>-- 
> >>Torbjørn
> >Back with results.
> >That's output from dmesg. If you need more, I can send netconsole
> >log as well.
> >
> Seems like the list did not accept the huge email.
> dmesg is available from:
> https://gist.github.com/anonymous/dba1f53211a1d482c3e0

This seems to be incomplete(Looks like dmesg has reached its buffer size limit),
does /var/log/message have the whole stack info?

thanks,
-liubo

> 
> --
> Torbjørn