Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755150AbbDKL71 (ORCPT ); Sat, 11 Apr 2015 07:59:27 -0400 Received: from ipmail05.adl6.internode.on.net ([150.101.137.143]:2105 "EHLO ipmail05.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752657AbbDKL7Z (ORCPT ); Sat, 11 Apr 2015 07:59:25 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A2C5BwBiCylVPM+HLHlcgwyBLoZCrEYBAQEBAQaRTwmHSQICAQECgTU5FAEBAQEBAQEGAQEBATg7hB8BAQEDAScTHCMQCAMOCgklDwUlAwcaE4giB810AQEBBwIBHxiFeIUbhCRYB4QtAQSbFIEehhyJZYNNhCMsMYEDgUABAQE Date: Sat, 11 Apr 2015 21:59:22 +1000 From: Dave Chinner To: Ming Lin Cc: Jens Axboe , Jens Axboe , lkml , linux-fsdevel@vger.kernel.org, ming.l@ssi.samsung.com Subject: Re: [PATCH 3/6] direct-io: add support for write stream IDs Message-ID: <20150411115922.GO13731@dastard> References: <1427210823-5283-1-git-send-email-axboe@fb.com> <1427210823-5283-4-git-send-email-axboe@fb.com> <20150325024328.GF31342@dastard> <5512C588.2050805@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3282 Lines: 91 On Fri, Apr 10, 2015 at 04:50:05PM -0700, Ming Lin wrote: > On Wed, Mar 25, 2015 at 7:26 AM, Jens Axboe wrote: > > On 03/24/2015 08:43 PM, Dave Chinner wrote: > >> > >> On Tue, Mar 24, 2015 at 09:27:00AM -0600, Jens Axboe wrote: > >>> > >>> Get the streamid from the file, if any, and set it on the bio. > >>> > >>> Signed-off-by: Jens Axboe > >>> --- > >>> fs/direct-io.c | 4 ++++ > >>> 1 file changed, 4 insertions(+) > >>> > >>> diff --git a/fs/direct-io.c b/fs/direct-io.c > >>> index e181b6b2e297..5d2750346451 100644 > >>> --- a/fs/direct-io.c > >>> +++ b/fs/direct-io.c > >>> @@ -77,6 +77,7 @@ struct dio_submit { > >>> int reap_counter; /* rate limit reaping */ > >>> sector_t final_block_in_request;/* doesn't change */ > >>> int boundary; /* prev block is at a boundary */ > >>> + int streamid; /* Write stream ID */ > >>> get_block_t *get_block; /* block mapping function */ > >>> dio_submit_t *submit_io; /* IO submition function */ > >>> > >>> @@ -372,6 +373,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit > >>> *sdio, > >>> > >>> sdio->bio = bio; > >>> sdio->logical_offset_in_bio = sdio->cur_page_fs_offset; > >>> + > >>> + bio_set_streamid(bio, sdio->streamid); > >>> } > >>> > >>> /* > >>> @@ -1205,6 +1208,7 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, > >>> struct inode *inode, > >>> sdio.blkbits = blkbits; > >>> sdio.blkfactor = i_blkbits - blkbits; > >>> sdio.block_in_file = offset >> blkbits; > >>> + sdio.streamid = iocb->ki_filp->f_streamid; > >> > >> > >> If iocb->ki_filp->f_streamid is not set, then it should fall back to > >> whatever is set on the inode->i_streamid. > > Why should do the fall back? Because then you have a method of using streams with applications that aren't aware of streams. Or perhaps you have a file you know has different access patterns to the rest of the files in a directory, and you don't want to have to set the stream on every process that opens and uses that file. e.g. database writeahead log files (sequential write, never read) vs database index/table files (random read/write)..... > > Good point, agree. Will make that change. > > That change causes problem for direct IO, for example > > process 1: > fd = open("/dev/nvme0n1", O_DIRECT...); > //set stream_id 1 > fadvise(fd, 1, 0, POSIX_FADV_STREAMID); > pwrite(fd, ....); > > process 2: > fd = open("/dev/nvme0n1", O_DIRECT...); > //should be legacy stream_id 0 > pwrite(fd, ....); > > But now process 2 also see stream_id 1, which is wrong. It's not wrong, your behaviour model is just different You have defined a process/fd based stream model and not considered considered that admins and applications might want to use a file based stream model instead, so applications don't need to even be aware that write streams are in use... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- 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/