Re: ext4: fix reference counting bug on block allocation error

[Greg KH <gregkh@linuxfoundation.org>]

On Sun, Aug 14, 2016 at 08:51:25PM +0200, Greg KH wrote:
> On Sun, Aug 14, 2016 at 08:37:56PM +0200, Vegard Nossum wrote:
> > On 08/14/2016 08:32 PM, Greg KH wrote:
> > > Hi Vegard and ext4 developers,
> > > 
> > > The patch below, in Linus's tree, references a patch in the Fixes: line
> > > that is not in Linus's tree (neither the git commit id, nor the subject
> > > line.)
> > > 
> > 
> > It seems to exist?
> > 
> > >> Fixes: 8556e8f3b6 ("ext4: Don't allow new groups to be added during block
> > allocation")
> > 
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8556e8f3b6c4c11601ce1e9ea8090a6d8bd5daae
> > 
> > > That's a bit confusing, what is this patch supposed to be fixing up?
> > > What stable tree(s) should it go to if the original patch it fixes isn't
> > > even in any tree?
> > 
> > The referenced commit adds the ext4_mb_release_context(ac); line which
> > is what is causing problems because that releases the context which is
> > still in fact in use.
> 
> Oh doh, sorry for the noise, I was only looking at 4.8-rc1 and older, my
> fault.

Hm, wait.  Commit 8556e8f3b6 didn't show up in my filters for some
reason (which it not good, and makes me worry), but also, it doesn't
apply to the stable trees at all.

So can you please send backports of that commit, and this one, if you
want them both queued up to any stable kernel tree?

thanks,

greg k-h