Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933460AbbDQPSf (ORCPT ); Fri, 17 Apr 2015 11:18:35 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:26591 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932416AbbDQPSd (ORCPT ); Fri, 17 Apr 2015 11:18:33 -0400 Message-ID: <553123F5.8040909@fb.com> Date: Fri, 17 Apr 2015 09:17:09 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Ming Lin , Jens Axboe CC: Dave Chinner , lkml , , Subject: Re: [PATCH 3/6] direct-io: add support for write stream IDs 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> In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.54.13] X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.13.68,1.0.33,0.0.0000 definitions=2015-04-17_06:2015-04-17,2015-04-17,1970-01-01 signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2961 Lines: 81 On 04/10/2015 05:50 PM, 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 the assumption is that, in general, the specific file is a good indication of the data lifetime, if someone has already set that. It's a better guess than writing without any stream attached. > 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. I guess for that case, it is a problem. Basically the fallback breaks down for full block devices, or huge files that are used as a general backing store (like a vm image, for instance). Hmm, not sure what the right solution would be here, or if there really is one. It's probably best NOT to do the fallback after all. -- Jens Axboe -- 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/