Re: [PATCH 07/10] dax: Add huge page fault support

From: Matthew Wilcox <willy@linux.intel.com>
To: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 07/10] dax: Add huge page fault support
Date: Mon, 13 Jul 2015 11:33:45 -0400	[thread overview]
Message-ID: <20150713153345.GI13681@linux.intel.com> (raw)
In-Reply-To: <20150713150500.GB17075@quack.suse.cz>

On Mon, Jul 13, 2015 at 05:05:00PM +0200, Jan Kara wrote:
> So if this is a writeable fault and we race with truncate, we can leave
> stale blocks beyond i_size, can't we? Ah, looking at dax_insert_mapping()
> this seems to be a documented quirk of DAX mmap code. Would be worth
> mentioning here as well so that people don't wonder...

Thanks!

-       /* Guard against a race with truncate */
+       /*
+        * If a truncate happened while we were allocating blocks, we may
+        * leave blocks allocated to the file that are beyond EOF.  We can't
+        * take i_mutex here, so just leave them hanging; they'll be freed
+        * when the file is deleted.
+        */

is what I'll commit.