From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754579Ab2G3ONQ (ORCPT ); Mon, 30 Jul 2012 10:13:16 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45574 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754446Ab2G3ONO (ORCPT ); Mon, 30 Jul 2012 10:13:14 -0400 Date: Mon, 30 Jul 2012 07:12:18 -0700 From: tip-bot for Oleg Nesterov Message-ID: Cc: linux-kernel@vger.kernel.org, anton@redhat.com, hpa@zytor.com, mingo@kernel.org, srikar@linux.vnet.ibm.com, oleg@redhat.com, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, anton@redhat.com, linux-kernel@vger.kernel.org, srikar@linux.vnet.ibm.com, tglx@linutronix.de, oleg@redhat.com In-Reply-To: <20120729182220.GA20322@redhat.com> References: <20120729182220.GA20322@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] uprobes: Clean up and document write_opcode()-> lock_page(old_page) Git-Commit-ID: 9f92448ceeea5326db7d114005a7e7ac03904edf X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.6 (terminus.zytor.com [127.0.0.1]); Mon, 30 Jul 2012 07:12:24 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 9f92448ceeea5326db7d114005a7e7ac03904edf Gitweb: http://git.kernel.org/tip/9f92448ceeea5326db7d114005a7e7ac03904edf Author: Oleg Nesterov AuthorDate: Sun, 29 Jul 2012 20:22:20 +0200 Committer: Ingo Molnar CommitDate: Mon, 30 Jul 2012 11:27:20 +0200 uprobes: Clean up and document write_opcode()->lock_page(old_page) The comment above write_opcode()->lock_page(old_page) tells about the race with do_wp_page(). I don't really understand which exactly race it means, but afaics this lock_page() was not enough to close all races with do_wp_page(). Anyway, since: 77fc4af1b59d uprobes: Change register_for_each_vma() to take mm->mmap_sem for writing this code is always called with ->mmap_sem held for writing, so we can forget about do_wp_page(). However, we can't simply remove this lock_page(), and the only (afaics) reason is __replace_page()->try_to_free_swap(). Nothing in write_opcode() needs it, move it into __replace_page() and fix the comment. Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju Cc: Anton Arapov Cc: Srikar Dronamraju Link: http://lkml.kernel.org/r/20120729182220.GA20322@redhat.com Signed-off-by: Ingo Molnar --- kernel/events/uprobes.c | 27 ++++++++++++++------------- 1 files changed, 14 insertions(+), 13 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 23c562b7..5db150b 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -139,10 +139,15 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, struct mm_struct *mm = vma->vm_mm; spinlock_t *ptl; pte_t *ptep; + int err; + /* freeze PageSwapCache() for try_to_free_swap() below */ + lock_page(page); + + err = -EAGAIN; ptep = page_check_address(page, mm, addr, &ptl, 0); if (!ptep) - return -EAGAIN; + goto unlock; get_page(kpage); page_add_new_anon_rmap(kpage, vma, addr); @@ -162,7 +167,10 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, put_page(page); pte_unmap_unlock(ptep, ptl); - return 0; + err = 0; + unlock: + unlock_page(page); + return err; } /** @@ -216,15 +224,10 @@ retry: ret = -ENOMEM; new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr); if (!new_page) - goto put_out; + goto put_old; __SetPageUptodate(new_page); - /* - * lock page will serialize against do_wp_page()'s - * PageAnon() handling - */ - lock_page(old_page); /* copy the page now that we've got it stable */ vaddr_old = kmap_atomic(old_page); vaddr_new = kmap_atomic(new_page); @@ -237,15 +240,13 @@ retry: ret = anon_vma_prepare(vma); if (ret) - goto unlock_out; + goto put_new; ret = __replace_page(vma, vaddr, old_page, new_page); -unlock_out: - unlock_page(old_page); +put_new: page_cache_release(new_page); - -put_out: +put_old: put_page(old_page); if (unlikely(ret == -EAGAIN))