Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757251Ab1FIIHk (ORCPT ); Thu, 9 Jun 2011 04:07:40 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59193 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754765Ab1FIIDA (ORCPT ); Thu, 9 Jun 2011 04:03:00 -0400 From: Mel Gorman To: Andrew Morton Cc: Linux-MM , Linux-Netdev , LKML , David Miller , Neil Brown , Peter Zijlstra , Mel Gorman Subject: [PATCH 04/14] mm: allow PF_MEMALLOC from softirq context Date: Thu, 9 Jun 2011 09:02:43 +0100 Message-Id: <1307606573-24704-5-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.7.3.4 In-Reply-To: <1307606573-24704-1-git-send-email-mgorman@suse.de> References: <1307606573-24704-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3097 Lines: 91 This is needed to allow network softirq packet processing to make use of PF_MEMALLOC. Currently softirq context cannot use PF_MEMALLOC due to it not being associated with a task, and therefore not having task flags to fiddle with - thus the gfp to alloc flag mapping ignores the task flags when in interrupts (hard or soft) context. Allowing softirqs to make use of PF_MEMALLOC therefore requires some trickery. We basically borrow the task flags from whatever process happens to be preempted by the softirq. So we modify the gfp to alloc flags mapping to not exclude task flags in softirq context, and modify the softirq code to save, clear and restore the PF_MEMALLOC flag. The save and clear, ensures the preempted task's PF_MEMALLOC flag doesn't leak into the softirq. The restore ensures a softirq's PF_MEMALLOC flag cannot leak back into the preempted process. Signed-off-by: Peter Zijlstra Signed-off-by: Mel Gorman --- include/linux/sched.h | 7 +++++++ kernel/softirq.c | 3 +++ mm/page_alloc.c | 5 ++++- 3 files changed, 14 insertions(+), 1 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 2a8621c..7f908f9 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1840,6 +1840,13 @@ static inline void rcu_copy_process(struct task_struct *p) #endif +static inline void tsk_restore_flags(struct task_struct *p, + unsigned long pflags, unsigned long mask) +{ + p->flags &= ~mask; + p->flags |= pflags & mask; +} + #ifdef CONFIG_SMP extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask); diff --git a/kernel/softirq.c b/kernel/softirq.c index 1396017..2817c27 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -210,6 +210,8 @@ asmlinkage void __do_softirq(void) __u32 pending; int max_restart = MAX_SOFTIRQ_RESTART; int cpu; + unsigned long pflags = current->flags; + current->flags &= ~PF_MEMALLOC; pending = local_softirq_pending(); account_system_vtime(current); @@ -265,6 +267,7 @@ restart: account_system_vtime(current); __local_bh_enable(SOFTIRQ_OFFSET); + tsk_restore_flags(current, pflags, PF_MEMALLOC); } #ifndef __ARCH_HAS_DO_SOFTIRQ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 27043e7..4e19606 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2046,7 +2046,10 @@ gfp_to_alloc_flags(gfp_t gfp_mask) if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) { if (gfp_mask & __GFP_MEMALLOC) alloc_flags |= ALLOC_NO_WATERMARKS; - else if (likely(!(gfp_mask & __GFP_NOMEMALLOC)) && !in_interrupt()) + else if (!in_irq() && (current->flags & PF_MEMALLOC)) + alloc_flags |= ALLOC_NO_WATERMARKS; + else if (!in_interrupt() && + unlikely(test_thread_flag(TIF_MEMDIE))) alloc_flags |= ALLOC_NO_WATERMARKS; } -- 1.7.3.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/