From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx143.postini.com [74.125.245.143]) by kanga.kvack.org (Postfix) with SMTP id 794F26B004A for ; Tue, 28 Feb 2012 07:17:29 -0500 (EST) Received: by vbbey12 with SMTP id ey12so1916058vbb.14 for ; Tue, 28 Feb 2012 04:17:28 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <87ipirclhe.fsf@linux.vnet.ibm.com> References: <1330280398-27956-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20120227151135.7d4076c6.akpm@linux-foundation.org> <87ipirclhe.fsf@linux.vnet.ibm.com> Date: Tue, 28 Feb 2012 20:17:28 +0800 Message-ID: Subject: Re: [PATCH] hugetlbfs: Add new rw_semaphore to fix truncate/read race From: Hillf Danton Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: "Aneesh Kumar K.V" Cc: Andrew Morton , linux-mm@kvack.org, mgorman@suse.de, kamezawa.hiroyu@jp.fujitsu.com, viro@zeniv.linux.org.uk, hughd@google.com, linux-kernel@vger.kernel.org On Tue, Feb 28, 2012 at 6:15 PM, Aneesh Kumar K.V wrote: > > Will update the patch with these details > A scratch is cooked, based on the -next tree, for accelerating your redelivery, if you like it, in which i_mutex is eliminated directly and page lock is used. -hd --- a/fs/hugetlbfs/inode.c Tue Feb 28 19:43:32 2012 +++ b/fs/hugetlbfs/inode.c Tue Feb 28 19:56:50 2012 @@ -245,17 +245,10 @@ static ssize_t hugetlbfs_read(struct fil loff_t isize; ssize_t retval = 0; - mutex_lock(&inode->i_mutex); - /* validate length */ if (len == 0) goto out; - isize = i_size_read(inode); - if (!isize) - goto out; - - end_index = (isize - 1) >> huge_page_shift(h); for (;;) { struct page *page; unsigned long nr, ret; @@ -263,6 +256,8 @@ static ssize_t hugetlbfs_read(struct fil /* nr is the maximum number of bytes to copy from this page */ nr = huge_page_size(h); + isize = i_size_read(inode); + end_index = isize >> huge_page_shift(h); if (index >= end_index) { if (index > end_index) goto out; @@ -274,7 +269,7 @@ static ssize_t hugetlbfs_read(struct fil nr = nr - offset; /* Find the page */ - page = find_get_page(mapping, index); + page = find_lock_page(mapping, index); if (unlikely(page == NULL)) { /* * We have a HOLE, zero out the user-buffer for the @@ -286,17 +281,30 @@ static ssize_t hugetlbfs_read(struct fil else ra = 0; } else { + unlock_page(page); + + /* Without i_mutex held, check isize again */ + nr = huge_page_size(h); + isize = i_size_read(inode); + end_index = isize >> huge_page_shift(h); + if (index == end_index) { + nr = isize & ~huge_page_mask(h); + if (nr <= offset) { + page_cache_release(page); + goto out; + } + } + nr -= offset; /* * We have the page, copy it to user space buffer. */ ra = hugetlbfs_read_actor(page, offset, buf, len, nr); ret = ra; + page_cache_release(page); } if (ra < 0) { if (retval == 0) retval = ra; - if (page) - page_cache_release(page); goto out; } @@ -306,16 +314,12 @@ static ssize_t hugetlbfs_read(struct fil index += offset >> huge_page_shift(h); offset &= ~huge_page_mask(h); - if (page) - page_cache_release(page); - /* short read or no more work */ if ((ret != nr) || (len == 0)) break; } out: *ppos = ((loff_t)index << huge_page_shift(h)) + offset; - mutex_unlock(&inode->i_mutex); return retval; } -- -- 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org