Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754554AbaAaXBf (ORCPT ); Fri, 31 Jan 2014 18:01:35 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:52234 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754183AbaAaXBd (ORCPT ); Fri, 31 Jan 2014 18:01:33 -0500 Date: Fri, 31 Jan 2014 15:00:58 -0800 From: Andrew Morton To: Alex Thorlton Cc: linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Rik van Riel , Mel Gorman , Jiang Liu , Peter Zijlstra , Oleg Nesterov , Ingo Molnar , "Eric W. Biederman" , Robin Holt , Al Viro , Kees Cook , liguang , linux-mm@kvack.org Subject: Re: [PATCH 2/3] Add VM_INIT_DEF_MASK and PRCTL_THP_DISABLE Message-Id: <20140131150058.99a9e70637f9b5112b8ab18f@linux-foundation.org> In-Reply-To: <1391192628-113858-5-git-send-email-athorlton@sgi.com> References: <1391192628-113858-1-git-send-email-athorlton@sgi.com> <1391192628-113858-5-git-send-email-athorlton@sgi.com> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 31 Jan 2014 12:23:45 -0600 Alex Thorlton wrote: > This patch adds a VM_INIT_DEF_MASK, to allow us to set the default flags > for VMs. It also adds a prctl control which alllows us to set the THP > disable bit in mm->def_flags so that VMs will pick up the setting as > they are created. > > ... > > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -177,6 +177,8 @@ extern unsigned int kobjsize(const void *objp); > */ > #define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP) > > +#define VM_INIT_DEF_MASK VM_NOHUGEPAGE Document this here? > /* > * mapping from the currently active vm_flags protection bits (the > * low four bits) to a page protection mask.. > diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h > index 289760f..58afc04 100644 > --- a/include/uapi/linux/prctl.h > +++ b/include/uapi/linux/prctl.h > @@ -149,4 +149,7 @@ > > #define PR_GET_TID_ADDRESS 40 > > +#define PR_SET_THP_DISABLE 41 > +#define PR_GET_THP_DISABLE 42 > + > #endif /* _LINUX_PRCTL_H */ > diff --git a/kernel/fork.c b/kernel/fork.c > index a17621c..9fc0a30 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -529,8 +529,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) > atomic_set(&mm->mm_count, 1); > init_rwsem(&mm->mmap_sem); > INIT_LIST_HEAD(&mm->mmlist); > - mm->flags = (current->mm) ? > - (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; > mm->core_state = NULL; > atomic_long_set(&mm->nr_ptes, 0); > memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); > @@ -539,8 +537,15 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) > mm_init_owner(mm, p); > clear_tlb_flush_pending(mm); > > - if (likely(!mm_alloc_pgd(mm))) { > + if (current->mm) { > + mm->flags = current->mm->flags & MMF_INIT_MASK; > + mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; So VM_INIT_DEF_MASK defines which vm flags a process may inherit from its parent? > + } else { > + mm->flags = default_dump_filter; > mm->def_flags = 0; > + } > + > + if (likely(!mm_alloc_pgd(mm))) { > mmu_notifier_mm_init(mm); > return mm; > } > diff --git a/kernel/sys.c b/kernel/sys.c > index c0a58be..d59524a 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -1996,6 +1996,23 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > if (arg2 || arg3 || arg4 || arg5) > return -EINVAL; > return current->no_new_privs ? 1 : 0; > + case PR_GET_THP_DISABLE: > + if (arg2 || arg3 || arg4 || arg5) > + return -EINVAL; Please add /* fall through */ here. So people don't think you added a bug. Also, iirc there's a static checking tool which will complain about this and there was talk about using the /* fall through */ to suppress the warning. > + case PR_SET_THP_DISABLE: > + if (arg3 || arg4 || arg5) > + return -EINVAL; > + down_write(&me->mm->mmap_sem); > + if (option == PR_SET_THP_DISABLE) { > + if (arg2) > + me->mm->def_flags |= VM_NOHUGEPAGE; > + else > + me->mm->def_flags &= ~VM_NOHUGEPAGE; > + } else { > + error = !!(me->mm->def_flags & VM_NOHUGEPAGE); > + } > + up_write(&me->mm->mmap_sem); > + break; I suspect it would be simpler to not try to combine the set and get code in the same lump. The prctl() extension should be added to user-facing documentation. Please work with Michael Kerrisk on that. -- 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/