From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f174.google.com (mail-wi0-f174.google.com [209.85.212.174]) by kanga.kvack.org (Postfix) with ESMTP id 978476B0255 for ; Tue, 22 Sep 2015 02:24:10 -0400 (EDT) Received: by wicge5 with SMTP id ge5so145561476wic.0 for ; Mon, 21 Sep 2015 23:24:10 -0700 (PDT) Received: from mail-wi0-x22c.google.com (mail-wi0-x22c.google.com. [2a00:1450:400c:c05::22c]) by mx.google.com with ESMTPS id bp5si48038wjc.7.2015.09.21.23.24.09 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 21 Sep 2015 23:24:09 -0700 (PDT) Received: by wicge5 with SMTP id ge5so145561039wic.0 for ; Mon, 21 Sep 2015 23:24:09 -0700 (PDT) From: Ingo Molnar Subject: [PATCH 02/11] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code Date: Tue, 22 Sep 2015 08:23:32 +0200 Message-Id: <1442903021-3893-3-git-send-email-mingo@kernel.org> In-Reply-To: <1442903021-3893-1-git-send-email-mingo@kernel.org> References: <1442903021-3893-1-git-send-email-mingo@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Waiman Long , Thomas Gleixner 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: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Waiman Long Cc: linux-mm@kvack.org Signed-off-by: Ingo Molnar --- arch/x86/mm/init_64.c | 38 ++++++++++++++++++++++++++------------ 1 file changed, 26 insertions(+), 12 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 30564e2752d3..7129e7647a76 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -33,6 +33,7 @@ #include #include #include +#include #include #include @@ -160,8 +161,8 @@ 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 +170,40 @@ 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; /* - * 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; + rcu_read_lock(); /* Task list walk */ spin_lock(&pgd_lock); - list_for_each_entry(page, &pgd_list, lru) { + + for_each_process(g) { + struct task_struct *p; + struct mm_struct *mm; pgd_t *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; + p = find_lock_task_mm(g); + if (!p) + continue; + + mm = p->mm; + pgd = mm->pgd; + + /* The pgt_lock is only used by Xen: */ + pgt_lock = &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)) @@ -202,8 +214,10 @@ void sync_global_pgds(unsigned long start, unsigned long end, int removed) } spin_unlock(pgt_lock); + task_unlock(p); } spin_unlock(&pgd_lock); + rcu_read_unlock(); } } -- 2.1.4 -- 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