From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 83B126B0044 for ; Sat, 5 Dec 2009 07:37:13 -0500 (EST) Date: Sat, 5 Dec 2009 12:37:00 +0000 (GMT) From: Hugh Dickins Subject: Re: [PATCH] hugetlb: Acquire the i_mmap_lock before walking the prio_tree to unmap a page In-Reply-To: <20091202221947.GB26702@csn.ul.ie> Message-ID: References: <20091202141930.GF1457@csn.ul.ie> <20091202221602.GA26702@csn.ul.ie> <20091202221947.GB26702@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Wed, 2 Dec 2009, Mel Gorman wrote: > On Wed, Dec 02, 2009 at 10:16:02PM +0000, Mel Gorman wrote: > > On Wed, Dec 02, 2009 at 08:13:39PM +0000, Hugh Dickins wrote: > > > > > > But the comment seems wrong to me: hugetlb_instantiation_mutex > > > guards against concurrent hugetlb_fault()s; but the structure of > > > the prio_tree shifts as vmas based on that inode are inserted into > > > (mmap'ed) and removed from (munmap'ed) that tree (always while > > > holding i_mmap_lock). I don't see hugetlb_instantiation_mutex > > > giving us any protection against this at present. > > > > > > > You're right of course. I'll report without that nonsense included. > > > > Actually, shouldn't the mmap_sem be protecting against concurrent mmap and > munmap altering the tree? The comment is still bogus of course. No, the mmap_sem can only protect against other threads sharing that same mm: whereas the prio_tree can shift around according to concurrent mmaps and munmaps of the same file in other mms. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org