Re: [merged] mm-fix-potential-data-race-in-sys_swapon.patch removed from -mm tree

[Mel Gorman <mgorman@techsingularity.net>]

On Mon, Aug 24, 2015 at 12:46:54PM -0700, Hugh Dickins wrote:
> Adding Mel to Cc.
> 
> On Mon, 24 Aug 2015, akpm@linux-foundation.org wrote:
> > 
> > The patch titled
> >      Subject: mm: fix potential data race in SyS_swapon
> > has been removed from the -mm tree.  Its filename was
> >      mm-fix-potential-data-race-in-sys_swapon.patch
> > 
> > This patch was dropped because it was merged into mainline or a subsystem tree
> 
> Administrative error?  I don't see this merged into mainline yet,
> and didn't see your usual mail when you send in a batch to Linus.
> 
> And I wouldn't want it rushed too quickly to Linus: that stable
> tag is barely justified, this is a very narrow race window that
> has gone unnoticed for years, and swapon requires CAP_SYS_ADMIN.
> 
> But also I spotted Mel proposing a swap-over-NFS patch in this area
> on LKML last Thursday: he appeared to be relying on the loop that I
> remove here, so he might want to veto this one (though can always
> reinstate what he needs later, if that's how it plays out).
> 

I don't think we will have a problem. The swap-over-NFS patch collides
with yours but not in a way that matters. I'll see how things look
after the merge window but I think I'll be able to limit the scope of
the lock further and still avoid the use of i_mutex.

-- 
Mel Gorman
SUSE Labs