From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 8832A8D0039 for ; Mon, 31 Jan 2011 10:41:24 -0500 (EST) From: Tao Ma Subject: [PATCH v2] mlock: set VM_WRITE in case we don't have read permission. Date: Mon, 31 Jan 2011 23:41:03 +0800 Message-Id: <1296488463-15179-1-git-send-email-tm@tao.ma> In-Reply-To: <20110131203943.4C77.A69D9226@jp.fujitsu.com> References: <20110131203943.4C77.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, KOSAKI Motohiro , Michel Lespinasse , Andrew Morton List-ID: From: Tao Ma In 5ecfda0, we do some optimization in mlock, but it causes a very basic test case(attached below) of mlock to fail. So this patch add another check that if we don't have read permission, still set FOLL_WRITE flag. Thank KOSAKI for the suggestion. The test program is attached below. #include #include #include #include #include #include #include #include int main() { char *buf, *testfile = "test_mmap"; int fd, file_len = 40960, ret = -1; fd = open(testfile, O_RDWR); if (fd < 0) { perror("open"); return -1; } if (ftruncate(fd, file_len) < 0) { perror("ftruncate"); goto out; } buf = mmap(NULL, file_len, PROT_WRITE, MAP_SHARED, fd, 0); if (buf == MAP_FAILED) { perror("mmap"); goto out; } if (mlock(buf, file_len) < 0) { perror("mlock"); goto out; } munlock(buf, file_len); munmap(buf, file_len); ret = 0; out: close(fd); return ret; } Cc: KOSAKI Motohiro Cc: Michel Lespinasse Cc: Andrew Morton Signed-off-by: Tao Ma --- mm/mlock.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index 13e81ee..8508c5a 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -178,6 +178,13 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma, if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE) gup_flags |= FOLL_WRITE; + /* + * We don't have readable permission. Therefore we can't use read + * operation even though it's faster. + */ + if ((vma->vm_flags & (VM_READ|VM_WRITE)) == VM_WRITE) + gup_flags |= FOLL_WRITE; + if (vma->vm_flags & VM_LOCKED) gup_flags |= FOLL_MLOCK; -- 1.6.3.GIT -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org