Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756541Ab3IMPUF (ORCPT ); Fri, 13 Sep 2013 11:20:05 -0400 Received: from relay.parallels.com ([195.214.232.42]:38131 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751901Ab3IMPUD (ORCPT ); Fri, 13 Sep 2013 11:20:03 -0400 Subject: [PATCH 1/2] fuse: wait for writeback in fuse_file_fallocate() -v3 To: miklos@szeredi.hu From: Maxim Patlasov Cc: fuse-devel@lists.sourceforge.net, bfoster@redhat.com, linux-kernel@vger.kernel.org, devel@openvz.org, xemul@parallels.com Date: Fri, 13 Sep 2013 19:19:54 +0400 Message-ID: <20130913151928.11415.44205.stgit@dhcp-10-30-17-2.sw.ru> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2535 Lines: 69 The patch fixes a race between mmap-ed write and fallocate(PUNCH_HOLE): 1) An user makes a page dirty via mmap-ed write. 2) The user performs fallocate(2) with mode == PUNCH_HOLE|KEEP_SIZE and covering the page. 3) Before truncate_pagecache_range call from fuse_file_fallocate, the page goes to write-back. The page is fully processed by fuse_writepage (including end_page_writeback on the page), but fuse_flush_writepages did nothing because fi->writectr < 0. 4) truncate_pagecache_range is called and fuse_file_fallocate is finishing by calling fuse_release_nowrite. The latter triggers processing queued write-back request which will write stale data to the hole soon. Changed in v2 (thanks to Brian for suggestion): - Do not truncate page cache until FUSE_FALLOCATE succeeded. Otherwise, we can end up in returning -ENOTSUPP while user data is already punched from page cache. Use filemap_write_and_wait_range() instead. Changed in v3 (thanks to Miklos for suggestion): - fuse_wait_on_writeback() is prone to livelocks; use fuse_set_nowrite() instead. So far as we need a dirty-page barrier only, fuse_sync_writes() should be enough. - rebased to for-linus branch of fuse.git Signed-off-by: Maxim Patlasov --- fs/fuse/file.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index d409dea..f9f07c4 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2484,8 +2484,15 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, if (lock_inode) { mutex_lock(&inode->i_mutex); - if (mode & FALLOC_FL_PUNCH_HOLE) - fuse_set_nowrite(inode); + if (mode & FALLOC_FL_PUNCH_HOLE) { + loff_t endbyte = offset + length - 1; + err = filemap_write_and_wait_range(inode->i_mapping, + offset, endbyte); + if (err) + goto out; + + fuse_sync_writes(inode); + } } req = fuse_get_req_nopages(fc); @@ -2520,11 +2527,8 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, fuse_invalidate_attr(inode); out: - if (lock_inode) { - if (mode & FALLOC_FL_PUNCH_HOLE) - fuse_release_nowrite(inode); + if (lock_inode) mutex_unlock(&inode->i_mutex); - } return err; } -- 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/