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 B2F086B006C for ; Thu, 9 Oct 2014 06:50:39 -0400 (EDT) Received: by mail-wi0-f174.google.com with SMTP id cc10so12724083wib.13 for ; Thu, 09 Oct 2014 03:50:39 -0700 (PDT) Received: from casper.infradead.org (casper.infradead.org. [2001:770:15f::2]) by mx.google.com with ESMTPS id gd4si17077838wib.6.2014.10.09.03.50.38 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 09 Oct 2014 03:50:38 -0700 (PDT) Date: Thu, 9 Oct 2014 12:50:37 +0200 From: Peter Zijlstra Subject: Re: [PATCH 2/4] mm: gup: add get_user_pages_locked and get_user_pages_unlocked Message-ID: <20141009105037.GM4750@worktop.programming.kicks-ass.net> References: <1412153797-6667-1-git-send-email-aarcange@redhat.com> <1412153797-6667-3-git-send-email-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412153797-6667-3-git-send-email-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andres Lagar-Cavilla , Gleb Natapov , Radim Krcmar , Paolo Bonzini , Rik van Riel , Mel Gorman , Andy Lutomirski , Andrew Morton , Sasha Levin , Jianyu Zhan , Paul Cassella , Hugh Dickins , Peter Feiner , "\\\"Dr. David Alan Gilbert\\\"" On Wed, Oct 01, 2014 at 10:56:35AM +0200, Andrea Arcangeli wrote: > +static inline long __get_user_pages_locked(struct task_struct *tsk, > + struct mm_struct *mm, > + unsigned long start, > + unsigned long nr_pages, > + int write, int force, > + struct page **pages, > + struct vm_area_struct **vmas, > + int *locked, > + bool notify_drop) > +{ > + if (notify_drop && lock_dropped && *locked) { > + /* > + * We must let the caller know we temporarily dropped the lock > + * and so the critical section protected by it was lost. > + */ > + up_read(&mm->mmap_sem); > + *locked = 0; > + } > + return pages_done; > +} > +long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm, > + unsigned long start, unsigned long nr_pages, > + int write, int force, struct page **pages, > + int *locked) > +{ > + return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, > + pages, NULL, locked, true); > +} > +long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, > + unsigned long start, unsigned long nr_pages, > + int write, int force, struct page **pages) > +{ > + long ret; > + int locked = 1; > + down_read(&mm->mmap_sem); > + ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, > + pages, NULL, &locked, false); > + if (locked) > + up_read(&mm->mmap_sem); > + return ret; > +} > long get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > unsigned long start, unsigned long nr_pages, int write, > int force, struct page **pages, struct vm_area_struct **vmas) > { > + return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force, > + pages, vmas, NULL, false); > } I'm wondering about that notify_drop parameter, what's the added benefit? If you look at these 3 callers we can do away with it, since in the second called where we have locked but !notify_drop we seem to do the exact same thing afterwards anyway. -- 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