Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 11 Jun 2002 02:13:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 11 Jun 2002 02:13:58 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:26632 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Tue, 11 Jun 2002 02:13:51 -0400 Message-ID: <3D0595F7.A21AE62B@zip.com.au> Date: Mon, 10 Jun 2002 23:17:27 -0700 From: Andrew Morton X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.19-pre9 i686) X-Accept-Language: en MIME-Version: 1.0 To: Keith Owens CC: linux-kernel@vger.kernel.org Subject: Re: 2.4.18 no timestamp update on modified mmapped files In-Reply-To: <10339.1023773628@kao2.melbourne.sgi.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Keith Owens wrote: > > fd = open("foo", O_RDWR); > map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); > ... modify the mapped pages ... > munmap(map, size); > close(fd); > > The timestamp on foo is not updated, even though the contents have > changed. Adding msync(map, size, MS_[A]SYNC) before munmap makes no > difference. 2.4.19-pre10 has no obvious fixes for this problem. > > I was tearing my hair out wondering why some files were not being > rsynced. No change on size or timestamp tells rsync that the file is > "unchanged". I had to add a dummy write(map, fd, 1) to force a > timestamp update. Well it's very easy to fix. And this (untested) patch will actually speed the kernel up (lots) because it has the smarter mtime update logic. But note that the mtime update won't occur for a (potentially infinitely) long time after your program has exited. Unless you used mysnc. What do the standards say? http://www.opengroup.org/onlinepubs/007904975/functions/mmap.html The st_ctime and st_mtime fields of a file that is mapped with MAP_SHARED and PROT_WRITE shall be marked for update at some point in the interval between a write reference to the mapped region and the next call to msync() with MS_ASYNC or MS_SYNC for that portion of the file by any process. If there is no such call and if the underlying file is modified as a result of a write reference, then these fields shall be marked for update at some time after the write reference. This patch does exactly that. Guess I should test it. --- 2.4.19-pre10/mm/vmscan.c~mmap-mtime Mon Jun 10 23:00:28 2002 +++ 2.4.19-pre10-akpm/mm/vmscan.c Mon Jun 10 23:04:34 2002 @@ -405,6 +405,9 @@ static int shrink_cache(int nr_pages, zo page_cache_get(page); spin_unlock(&pagemap_lru_lock); + if (!PageSwapCache(page)) + update_mtime(page->mapping->host); + writepage(page); page_cache_release(page); --- 2.4.19-pre10/mm/filemap.c~mmap-mtime Mon Jun 10 23:00:31 2002 +++ 2.4.19-pre10-akpm/mm/filemap.c Mon Jun 10 23:05:17 2002 @@ -551,6 +551,9 @@ int filemap_fdatasync(struct address_spa int ret = 0; int (*writepage)(struct page *) = mapping->a_ops->writepage; + if (!list_empty(&mapping->dirty_pages)) + update_mtime(mapping->host); + spin_lock(&pagecache_lock); while (!list_empty(&mapping->dirty_pages)) { @@ -3026,8 +3029,7 @@ generic_file_write(struct file *file,con goto out; remove_suid(inode); - inode->i_ctime = inode->i_mtime = CURRENT_TIME; - mark_inode_dirty_sync(inode); + update_mtime(inode); if (file->f_flags & O_DIRECT) goto o_direct; --- 2.4.19-pre10/fs/inode.c~mmap-mtime Mon Jun 10 23:02:18 2002 +++ 2.4.19-pre10-akpm/fs/inode.c Mon Jun 10 23:03:18 2002 @@ -1195,6 +1195,16 @@ void update_atime (struct inode *inode) mark_inode_dirty_sync (inode); } /* End Function update_atime */ +void update_mtime(struct inode *inode) +{ + time_t now = CURRENT_TIME; + + if (inode->i_ctime != now || inode->i_mtime != now) { + inode->i_ctime = now; + inode->i_mtime = now; + mark_inode_dirty_sync(inode); + } +} /* * Quota functions that want to walk the inode lists.. --- 2.4.19-pre10/include/linux/fs.h~mmap-mtime Mon Jun 10 23:02:21 2002 +++ 2.4.19-pre10-akpm/include/linux/fs.h Mon Jun 10 23:03:41 2002 @@ -200,7 +200,8 @@ extern int leases_enable, dir_notify_ena #include #include -extern void update_atime (struct inode *); +void update_atime(struct inode *); +void update_mtime(struct inode *); #define UPDATE_ATIME(inode) update_atime (inode) extern void buffer_init(unsigned long); - - 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/