From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757860Ab3HMMJW (ORCPT ); Tue, 13 Aug 2013 08:09:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53614 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757830Ab3HMMJT (ORCPT ); Tue, 13 Aug 2013 08:09:19 -0400 Message-ID: <520A2114.1040203@redhat.com> Date: Tue, 13 Aug 2013 08:05:40 -0400 From: Brian Foster User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Maxim Patlasov CC: miklos@szeredi.hu, fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, devel@openvz.org, xemul@parallels.com Subject: Re: [PATCH 2/2] fuse: wait for writeback in fuse_file_fallocate() References: <20130812163739.10366.64896.stgit@maximpc.sw.ru> <20130812163935.10366.88320.stgit@maximpc.sw.ru> In-Reply-To: <20130812163935.10366.88320.stgit@maximpc.sw.ru> 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 On 08/12/2013 12:39 PM, Maxim Patlasov wrote: > 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 date to the hole soon. > > Signed-off-by: Maxim Patlasov > --- Hi Maxim, Nice catch and description, one minor concern... > fs/fuse/file.c | 53 ++++++++++++++++++++++++++++++++++++++++++++--------- > 1 files changed, 44 insertions(+), 9 deletions(-) > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > index d1715b3..2b18c4b 100644 > --- a/fs/fuse/file.c > +++ b/fs/fuse/file.c > @@ -344,6 +344,31 @@ static bool fuse_page_is_writeback(struct inode *inode, pgoff_t index) > return found; > } > > +static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from, > + pgoff_t idx_to) > +{ > + struct fuse_conn *fc = get_fuse_conn(inode); > + struct fuse_inode *fi = get_fuse_inode(inode); > + struct fuse_req *req; > + bool found = false; > + > + spin_lock(&fc->lock); > + list_for_each_entry(req, &fi->writepages, writepages_entry) { > + pgoff_t curr_index; > + > + BUG_ON(req->inode != inode); > + curr_index = req->misc.write.in.offset >> PAGE_CACHE_SHIFT; > + if (!(idx_from >= curr_index + req->num_pages || > + idx_to < curr_index)) { > + found = true; > + break; > + } > + } > + spin_unlock(&fc->lock); > + > + return found; > +} > + > /* > * Wait for page writeback to be completed. > * > @@ -358,6 +383,19 @@ static int fuse_wait_on_page_writeback(struct inode *inode, pgoff_t index) > return 0; > } > > +static void fuse_wait_on_writeback(struct inode *inode, pgoff_t start, > + size_t bytes) > +{ > + struct fuse_inode *fi = get_fuse_inode(inode); > + pgoff_t idx_from, idx_to; > + > + idx_from = start >> PAGE_CACHE_SHIFT; > + idx_to = (start + bytes - 1) >> PAGE_CACHE_SHIFT; > + > + wait_event(fi->page_waitq, > + !fuse_range_is_writeback(inode, idx_from, idx_to)); > +} > + > static int fuse_flush(struct file *file, fl_owner_t id) > { > struct inode *inode = file_inode(file); > @@ -2478,8 +2516,11 @@ 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) { > + truncate_pagecache_range(inode, offset, > + offset + length - 1); > + fuse_wait_on_writeback(inode, offset, length); > + } If this happens to be the first attempt on an fs that doesn't support fallocate, we'll return -EOPNOTSUPP after having already punched out the data in the pagecache. What about replacing the nowrite logic with a flush (and still followed by your new writeback wait logic) rather than moving the pagecache truncate? Brian > } > > req = fuse_get_req_nopages(fc); > @@ -2508,17 +2549,11 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, > if (!(mode & FALLOC_FL_KEEP_SIZE)) > fuse_write_update_size(inode, offset + length); > > - if (mode & FALLOC_FL_PUNCH_HOLE) > - truncate_pagecache_range(inode, offset, offset + length - 1); > - > 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; > } >