From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753923AbcAVPLf (ORCPT ); Fri, 22 Jan 2016 10:11:35 -0500 Received: from mx2.suse.de ([195.135.220.15]:34248 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753842AbcAVPLb (ORCPT ); Fri, 22 Jan 2016 10:11:31 -0500 Date: Fri, 22 Jan 2016 16:11:41 +0100 From: Jan Kara To: Ross Zwisler Cc: linux-kernel@vger.kernel.org, Alexander Viro , Andrew Morton , Dan Williams , Dave Chinner , Jan Kara , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-nvdimm@ml01.01.org Subject: Re: [PATCH v2 4/5] dax: fix PMD handling for fsync/msync Message-ID: <20160122151141.GM16898@quack.suse.cz> References: <1453398364-22537-1-git-send-email-ross.zwisler@linux.intel.com> <1453398364-22537-5-git-send-email-ross.zwisler@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1453398364-22537-5-git-send-email-ross.zwisler@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 21-01-16 10:46:03, Ross Zwisler wrote: > Fix the way that DAX PMD radix tree entries are handled. With this patch > we now check to see if a PMD entry exists in the radix tree on write, even > if we are just trying to insert a PTE. If it exists, we dirty that instead > of inserting our own PTE entry. > > Fix a bug in the PMD path in dax_writeback_mapping_range() where we were > previously passing a loff_t into radix_tree_lookup instead of a pgoff_t. Ah, good catch! > Account for the fact that multiple fsync/msync operations may be happening > at the same time and don't flush entries that are beyond end_index. > > Signed-off-by: Ross Zwisler Just one nit below. You can add: Reviewed-by: Jan Kara > --- > fs/dax.c | 39 +++++++++++++++++++++++++++------------ > 1 file changed, 27 insertions(+), 12 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index 55ae394..afacc30 100644 > --- a/fs/dax.c > +++ b/fs/dax.c ... > @@ -460,31 +468,33 @@ int dax_writeback_mapping_range(struct address_space *mapping, loff_t start, > { > struct inode *inode = mapping->host; > struct block_device *bdev = inode->i_sb->s_bdev; > + pgoff_t start_index, end_index, pmd_index; > pgoff_t indices[PAGEVEC_SIZE]; > - pgoff_t start_page, end_page; > struct pagevec pvec; > - void *entry; > + bool done = false; > int i, ret = 0; > + void *entry; > > if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) > return -EIO; > > + start_index = start >> PAGE_CACHE_SHIFT; > + end_index = end >> PAGE_CACHE_SHIFT; > + pmd_index = DAX_PMD_INDEX(start_index); > + > rcu_read_lock(); > - entry = radix_tree_lookup(&mapping->page_tree, start & PMD_MASK); > + entry = radix_tree_lookup(&mapping->page_tree, pmd_index); > rcu_read_unlock(); > > /* see if the start of our range is covered by a PMD entry */ > - if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) > - start &= PMD_MASK; > - > - start_page = start >> PAGE_CACHE_SHIFT; > - end_page = end >> PAGE_CACHE_SHIFT; > + if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) Don't you miss a check that entry != NULL? I agree that RADIX_DAX_TYPE(NULL) is != from RADIX_DAX_PMD so it works as desired but it looks a bit dangerous. Honza -- Jan Kara SUSE Labs, CR