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:

quoted

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