From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932922AbbFKOHq (ORCPT ); Thu, 11 Jun 2015 10:07:46 -0400 Received: from mail-wg0-f51.google.com ([74.125.82.51]:33653 "EHLO mail-wg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932088AbbFKOHh (ORCPT ); Thu, 11 Jun 2015 10:07:37 -0400 From: Ingo Molnar To: linux-kernel@vger.kernel.org Cc: linux-mml@vger.kernel.org, Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Thomas Gleixner , Waiman Long Subject: [PATCH 02/12] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code Date: Thu, 11 Jun 2015 16:07:07 +0200 Message-Id: <1434031637-9091-3-git-send-email-mingo@kernel.org> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1434031637-9091-1-git-send-email-mingo@kernel.org> References: <1434031637-9091-1-git-send-email-mingo@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The memory hotplug code uses sync_global_pgds() to synchronize updates to the global (&init_mm) kernel PGD and the task PGDs. It does this by iterating over the pgd_list - which list closely tracks task creation/destruction via fork/clone. But we want to remove this list, so that it does not have to be maintained from fork()/exit(), so convert the memory hotplug code to use the task list to iterate over all pgds in the system. Also improve the comments a bit, to make this function easier to understand. Only lightly tested, as I don't have a memory hotplug setup. Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Waiman Long Signed-off-by: Ingo Molnar --- arch/x86/mm/init_64.c | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 3fba623e3ba5..1921acbd49fd 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -160,8 +160,8 @@ static int __init nonx32_setup(char *str) __setup("noexec32=", nonx32_setup); /* - * When memory was added/removed make sure all the processes MM have - * suitable PGD entries in the local PGD level page. + * When memory was added/removed make sure all the process MMs have + * matching PGD entries in the local PGD level page as well. */ void sync_global_pgds(unsigned long start, unsigned long end, int removed) { @@ -169,29 +169,33 @@ void sync_global_pgds(unsigned long start, unsigned long end, int removed) for (address = start; address <= end; address += PGDIR_SIZE) { const pgd_t *pgd_ref = pgd_offset_k(address); - struct page *page; + struct task_struct *g, *p; /* - * When it is called after memory hot remove, pgd_none() - * returns true. In this case (removed == 1), we must clear - * the PGD entries in the local PGD level page. + * When this function is called after memory hot remove, + * pgd_none() already returns true, but only the reference + * kernel PGD has been cleared, not the process PGDs. + * + * So clear the affected entries in every process PGD as well: */ if (pgd_none(*pgd_ref) && !removed) continue; spin_lock(&pgd_lock); - list_for_each_entry(page, &pgd_list, lru) { - pgd_t *pgd; + + for_each_process_thread(g, p) { + pgd_t *pgd = p->mm->pgd; spinlock_t *pgt_lock; - pgd = (pgd_t *)page_address(page) + pgd_index(address); - /* the pgt_lock only for Xen */ - pgt_lock = &pgd_page_get_mm(page)->page_table_lock; + if (!p->mm) + continue; + + /* The pgt_lock is only used by Xen: */ + pgt_lock = &p->mm->page_table_lock; spin_lock(pgt_lock); if (!pgd_none(*pgd_ref) && !pgd_none(*pgd)) - BUG_ON(pgd_page_vaddr(*pgd) - != pgd_page_vaddr(*pgd_ref)); + BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); if (removed) { if (pgd_none(*pgd_ref) && !pgd_none(*pgd)) -- 2.1.4