Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751240AbcDOR5b (ORCPT ); Fri, 15 Apr 2016 13:57:31 -0400 Received: from mail-ob0-f173.google.com ([209.85.214.173]:32817 "EHLO mail-ob0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751104AbcDOR52 (ORCPT ); Fri, 15 Apr 2016 13:57:28 -0400 MIME-Version: 1.0 In-Reply-To: <1460741821.3012.11.camel@intel.com> References: <1459303190-20072-1-git-send-email-vishal.l.verma@intel.com> <1459303190-20072-6-git-send-email-vishal.l.verma@intel.com> <1460739288.3012.3.camel@intel.com> <1460741821.3012.11.camel@intel.com> Date: Fri, 15 Apr 2016 10:57:27 -0700 Message-ID: Subject: Re: [PATCH v2 5/5] dax: handle media errors in dax_do_io From: Dan Williams To: "Verma, Vishal L" Cc: "jmoyer@redhat.com" , "hch@infradead.org" , "jack@suse.cz" , "axboe@fb.com" , "linux-nvdimm@ml01.01.org" , "david@fromorbit.com" , "linux-kernel@vger.kernel.org" , "xfs@oss.sgi.com" , "linux-block@vger.kernel.org" , "linux-mm@kvack.org" , "viro@zeniv.linux.org.uk" , "linux-fsdevel@vger.kernel.org" , "akpm@linux-foundation.org" , "linux-ext4@vger.kernel.org" , "Wilcox, Matthew R" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 37 On Fri, Apr 15, 2016 at 10:37 AM, Verma, Vishal L wrote: > On Fri, 2016-04-15 at 13:11 -0400, Jeff Moyer wrote: [..] >> > >> > But, how does _EIOCBQUEUED work? Maybe we need an exception for it? >> For async direct I/O, only the setup phase of the I/O is performed >> and >> then we return to the caller. -EIOCBQUEUED signifies this. >> >> You're heading towards code that looks like this: >> >> if (IS_DAX(inode)) { >> ret = dax_do_io(iocb, inode, iter, offset, >> blkdev_get_block, >> NULL, DIO_SKIP_DIO_COUNT); >> if (ret == -EIO && (iov_iter_rw(iter) == WRITE)) >> ret_saved = ret; >> else >> return ret; >> } >> >> ret = __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, >> offset, >> blkdev_get_block, NULL, NULL, >> DIO_SKIP_DIO_COUNT); >> if (ret < 0 && ret != -EIOCBQUEUED && ret_saved) >> return ret_saved; >> >> There's a lot of special casing here, so you might consider adding >> comments. > > Correct - maybe we should reconsider wrapper-izing this? :) Another option is just to skip dax_do_io() and this special casing fallback entirely if errors are present. I.e. only attempt dax_do_io when: IS_DAX() && gendisk->bb && bb->count == 0.