From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752318AbbBLV7Z (ORCPT ); Thu, 12 Feb 2015 16:59:25 -0500 Received: from mail-ie0-f179.google.com ([209.85.223.179]:34395 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750959AbbBLV7Y (ORCPT ); Thu, 12 Feb 2015 16:59:24 -0500 Date: Thu, 12 Feb 2015 13:59:22 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: "Kirill A. Shutemov" cc: "Kirill A. Shutemov" , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Linus Torvalds , Michel Lespinasse , Rik van Riel Subject: Re: [PATCH 2/4] mm: rename __mlock_vma_pages_range() to populate_vma_page_range() In-Reply-To: <20150212110318.GA15658@node.dhcp.inet.fi> Message-ID: References: <1423674728-214192-1-git-send-email-kirill.shutemov@linux.intel.com> <1423674728-214192-3-git-send-email-kirill.shutemov@linux.intel.com> <20150212110318.GA15658@node.dhcp.inet.fi> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 12 Feb 2015, Kirill A. Shutemov wrote: > > I think it makes sense to drop the references about "downgrading" > > mm->mmap_sem in the documentation since populate_vma_page_range() can be > > called with it held either for read or write depending on the context. > > I'm not sure what references you're talking about. > > Is it about this part: > > * If @nonblocking is non-NULL, it must held for read only and may be > * released. If it's released, *@nonblocking will be set to 0. > > ? > No, I was agreeing with your removal from the documentation: @@ -463,21 +463,11 @@ populate the page table. To mlock a range of memory under the unevictable/mlock infrastructure, the mmap() handler and task address space expansion functions call -mlock_vma_pages_range() specifying the vma and the address range to mlock. -mlock_vma_pages_range() filters VMAs like mlock_fixup(), as described above in -"Filtering Special VMAs". It will clear the VM_LOCKED flag, which will have -already been set by the caller, in filtered VMAs. Thus these VMA's need not be -visited for munlock when the region is unmapped. - -For "normal" VMAs, mlock_vma_pages_range() calls __mlock_vma_pages_range() to -fault/allocate the pages and mlock them. Again, like mlock_fixup(), -mlock_vma_pages_range() downgrades the mmap semaphore to read mode before -attempting to fault/allocate and mlock the pages and "upgrades" the semaphore -back to write mode before returning. - -The callers of mlock_vma_pages_range() will have already added the memory range +populate_vma_page_range() specifying the vma and the address range to mlock. + +The callers of populate_vma_page_range() will have already added the memory range to be mlocked to the task's "locked_vm". To account for filtered VMAs, -mlock_vma_pages_range() returns the number of pages NOT mlocked. All of the +populate_vma_page_range() returns the number of pages NOT mlocked. All of the callers then subtract a non-negative return value from the task's locked_vm. A negative return value represent an error - for example, from get_user_pages() attempting to fault in a VMA with PROT_NONE access. In this case, we leave the