From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0627C77B7D for ; Fri, 5 May 2023 22:47:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232541AbjEEWrY (ORCPT ); Fri, 5 May 2023 18:47:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229545AbjEEWrX (ORCPT ); Fri, 5 May 2023 18:47:23 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79FF74EC0; Fri, 5 May 2023 15:47:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F19136412D; Fri, 5 May 2023 22:47:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE4B0C433D2; Fri, 5 May 2023 22:47:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683326841; bh=D0qbriAJbRPAwi0B8rnE/70zyZxx/MoRWZ/NxcKY3o4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DYLwKlKdOz6DTtddRRpzE/g5GUU5YeP9nw5j3gbN5Oz8o/mRC/Tq3TL4r8inm1/5v zCQxxwI42ekZKTzyB4UpzNeEHV8K12BxmOw3f/930wcqHv3deUCbnP/y6LoW3L0xzX tw4sbrAehxrxSzE3UA9ERBQjlnAQMcJcQ0ueaneOY4ffcP/7P8CORy9MiNBmPtCKiT QVlfg70i8qpYpGRLOP1VuVwqBo4hFm+BKzhtU/KyHNOcWRSUUR8Z5lmZs2GavGCrBR NCH4Ig18O2PysnslWZU0MjaS8vFR6Rlwh85P1WfQXTluAmwcLcbicIbNC4DMbbVoui YQltmUUIC6f6A== Date: Fri, 5 May 2023 22:47:19 +0000 From: Eric Biggers To: Dave Chinner Cc: John Garry , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, martin.petersen@oracle.com, djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, dchinner@redhat.com, jejb@linux.ibm.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, Himanshu Madhani Subject: Re: [PATCH RFC 01/16] block: Add atomic write operations to request_queue limits Message-ID: References: <20230503183821.1473305-1-john.g.garry@oracle.com> <20230503183821.1473305-2-john.g.garry@oracle.com> <20230503213925.GD3223426@dread.disaster.area> <20230504222623.GI3223426@dread.disaster.area> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230504222623.GI3223426@dread.disaster.area> Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Fri, May 05, 2023 at 08:26:23AM +1000, Dave Chinner wrote: > > ok, we can do that but would also then make statx field 64b. I'm fine with > > that if it is wise to do so - I don't don't want to wastefully use up an > > extra 2 x 32b in struct statx. > > Why do we need specific varibles for DIO atomic write alignment > limits? We already have direct IO alignment and size constraints in statx(), > so why wouldn't we just reuse those variables when the user requests > atomic limits for DIO? > > i.e. if STATX_DIOALIGN is set, we return normal DIO alignment > constraints. If STATX_DIOALIGN_ATOMIC is set, we return the atomic > DIO alignment requirements in those variables..... > > Yes, we probably need the dio max size to be added to statx for > this. Historically speaking, I wanted statx to support this in the > first place because that's what we were already giving userspace > with XFS_IOC_DIOINFO and we already knew that atomic IO when it came > along would require a bound maximum IO size much smaller than normal > DIO limits. i.e.: > > struct dioattr { > __u32 d_mem; /* data buffer memory alignment */ > __u32 d_miniosz; /* min xfer size */ > __u32 d_maxiosz; /* max xfer size */ > }; > > where d_miniosz defined the alignment and size constraints for DIOs. > > If we simply document that STATX_DIOALIGN_ATOMIC returns minimum > (unit) atomic IO size and alignment in statx->dio_offset_align (as > per STATX_DIOALIGN) and the maximum atomic IO size in > statx->dio_max_iosize, then we don't burn up anywhere near as much > space in the statx structure.... I don't think that's how statx() is meant to work. The request mask is a bitmask, and the user can request an arbitrary combination of different items. For example, the user could request both STATX_DIOALIGN and STATX_WRITE_ATOMIC at the same time. That doesn't work if different items share the same fields. - Eric