From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dave <dave@sr71.net>
Subject: Re: [PATCHv2, RFC 18/30] thp, mm: truncate support for transparent
 huge page cache
Date: Fri, 22 Mar 2013 11:29:57 -0700
Message-ID: <514CA325.3010104@sr71.net>
References: <1363283435-7666-1-git-send-email-kirill.shutemov@linux.intel.com> <1363283435-7666-19-git-send-email-kirill.shutemov@linux.intel.com>
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Cc: Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Hugh Dickins <hughd@google.com>,
	Wu Fengguang <fengguang.wu@intel.com>, Jan Kara <jack@suse.cz>,
	Mel Gorman <mgorman@suse.de>, linux-mm@kvack.org,
	Andi Kleen <ak@linux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@intel.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Hillf Danton <dhillf@gmail.com>, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <1363283435-7666-19-git-send-email-kirill.shutemov@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On 03/14/2013 10:50 AM, Kirill A. Shutemov wrote:
> @@ -280,6 +291,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
>  			if (index > end)
>  				break;
>  
> +			VM_BUG_ON(PageTransHuge(page));
>  			lock_page(page);
>  			WARN_ON(page->index != index);
>  			wait_on_page_writeback(page);

This looks to be during the second truncate pass where things are
allowed to block.  What's the logic behind it not being possible to
encounter TransHugePage()s here?