Re: [PATCH 09/10] huge pagecache: mmap_sem is unlocked when truncation splits pmd

[Andrew Morton]

On Thu, 14 Apr 2016 13:39:22 -0400 Matthew Wilcox <willy@xxxxxxxxxxxxxxx> wrote:

> On Tue, Apr 05, 2016 at 01:55:23PM -0700, Hugh Dickins wrote:
> > zap_pmd_range()'s CONFIG_DEBUG_VM !rwsem_is_locked(&mmap_sem) BUG()
> > will be invalid with huge pagecache, in whatever way it is implemented:
> > truncation of a hugely-mapped file to an unhugely-aligned size would
> > easily hit it.
> 
> We can reproduce this BUG() in the current Linus tree with DAX PMDs.
> Andrew, can you send this patch to Linus for inclusion in 4.7?

Wilco, thanks.