From: Jan Kara Subject: Re: [PATCH 11/13] dax, iomap: Add support for synchronous faults Date: Tue, 22 Aug 2017 11:46:55 +0200 Message-ID: <20170822094655.GE4909@quack2.suse.cz> References: <20170817160815.30466-1-jack@suse.cz> <20170817160815.30466-12-jack@suse.cz> <20170821185830.GB26220@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, Andy Lutomirski , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, Christoph Hellwig , Dan Williams , Boaz Harrosh To: Ross Zwisler Return-path: Received: from mx2.suse.de ([195.135.220.15]:47766 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932305AbdHVJq5 (ORCPT ); Tue, 22 Aug 2017 05:46:57 -0400 Content-Disposition: inline In-Reply-To: <20170821185830.GB26220@linux.intel.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon 21-08-17 12:58:30, Ross Zwisler wrote: > On Thu, Aug 17, 2017 at 06:08:13PM +0200, Jan Kara wrote: > > Add a flag to iomap interface informing the caller that inode needs > > fdstasync(2) for returned extent to become persistent and use it in DAX > > fault code so that we map such extents only read only. We propagate the > > information that the page table entry has been inserted write-protected > > from dax_iomap_fault() with a new VM_FAULT_RO flag. Filesystem fault > > handler is then responsible for calling fdatasync(2) and updating page > > tables to map pfns read-write. dax_iomap_fault() also takes care of > > updating vmf->orig_pte to match the PTE that was inserted so that we can > > safely recheck that PTE did not change while write-enabling it. > > This changelog needs a little love. s/VM_FAULT_RO/VM_FAULT_NEEDDSYNC/, the > new path doesn't do the RO mapping, but instead just does the entire RW > mapping after the fdatasync is complete, the vmf->orig_pte manipulation went > away, etc. Yeah, fixed. Thanks for noticing. > > Signed-off-by: Jan Kara > > --- > > fs/dax.c | 31 +++++++++++++++++++++++++++++++ > > include/linux/iomap.h | 2 ++ > > include/linux/mm.h | 6 +++++- > > 3 files changed, 38 insertions(+), 1 deletion(-) > > > > diff --git a/fs/dax.c b/fs/dax.c > > index bc040e654cc9..ca88fc356786 100644 > > --- a/fs/dax.c > > +++ b/fs/dax.c > > @@ -1177,6 +1177,22 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, > > goto error_finish_iomap; > > } > > > > + /* > > + * If we are doing synchronous page fault and inode needs fsync, > > + * we can insert PTE into page tables only after that happens. > > + * Skip insertion for now and return the pfn so that caller can > > + * insert it after fsync is done. > > + */ > > + if (write && (vma->vm_flags & VM_SYNC) && > > + (iomap.flags & IOMAP_F_NEEDDSYNC)) { > > Just a small nit, but I don't think we really need to check for 'write' here. > The fact that IOMAP_F_NEEDDSYNC is set tells us that we are doing a write. > > if ((flags & IOMAP_WRITE) && > !jbd2_transaction_committed(EXT4_SB(inode->i_sb)->s_journal, > EXT4_I(inode)->i_datasync_tid)) > iomap->flags |= IOMAP_F_NEEDDSYNC; > > Ditto for the PMD case. OK, done. > With that one simplification and a cleaned up changelog, you can add: > > Reviewed-by: Ross Zwisler Thanks. Honza -- Jan Kara SUSE Labs, CR