Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752481AbbDQGU6 (ORCPT ); Fri, 17 Apr 2015 02:20:58 -0400 Received: from mail.kernel.org ([198.145.29.136]:58969 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751370AbbDQGUt (ORCPT ); Fri, 17 Apr 2015 02:20:49 -0400 MIME-Version: 1.0 In-Reply-To: <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> <20150411115922.GO13731@dastard> Date: Thu, 16 Apr 2015 23:20:45 -0700 Message-ID: Subject: Re: [PATCH 3/6] direct-io: add support for write stream IDs From: Ming Lin To: Dave Chinner Cc: Ming Lin , Jens Axboe , Jens Axboe , lkml , linux-fsdevel@vger.kernel.org, ming.l@ssi.samsung.com, "Kwan (Hingkwan) Huen-SSI" 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: 3997 Lines: 108 On Sat, Apr 11, 2015 at 4:59 AM, Dave Chinner wrote: > 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... The stream must be opened, otherwise device will return error if application write to a not-opened stream. Device has limited number of streams, for example, 16 streams. There are 2 APIs to open/close the stream. process 1: fd = open("/dev/nvme0n1", O_DIRECT...); stream_id = open_stream("/dev/nvme0n1", ....); fadvise(fd, stream_id, 0, POSIX_FADV_STREAMID); pwrite(fd, ....); close_stream("/dev/nvme0n1", stream_id); process 2: fd = open("/dev/nvme0n1", O_DIRECT...); //should be legacy stream_id 0 pwrite(fd, ....); Now process 2 gets error because the "stream_id" was already closed. Thanks, Ming -- 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/