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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B7941C7EE24 for ; Sat, 6 May 2023 00:08:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=F8b1QrBm7NAy/H5JZI9VBQ4yDERr4fwkVzpazVyX0h4=; b=Pumy02hpUabLj5VWkC546RDRuw MfKJlKvbDF0zNYrBxlW5TfZQz7laoRYYFfhwZ0Alu2SvvyuvnepNGcA/eQuitAWynm4w8xpAjw6WR u7Rjm6VAHGwuoaZanKTsNXs//kBqG2m0SzP0yIejiFdvc1fXB+j981pwYxIFD8ceIIX8yU1RJEpmT iKy9rpKu/n5QHgdRsWpW1DIPbni7wTNWjOh36jYk+g+Fda1mq3a8AMQi0lyaELkN6h56xuZ5PrGm+ vDf3FgZ4WEvNtUkPY7jGR2DHlkq51aBDgcXU5gF7t7hnyn6CCi/fu3aoHCq7g/23dJc1AlnhW3u8w 4d40Ntug==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pv5TR-00C98I-13; Sat, 06 May 2023 00:08:29 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pv5TN-00C97G-1u for linux-nvme@lists.infradead.org; Sat, 06 May 2023 00:08:27 +0000 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 ED0AD61575; Sat, 6 May 2023 00:08:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAD13C433EF; Sat, 6 May 2023 00:08:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683331704; bh=7+4RZ/Snpwvb0zzhi2RjjXRKKk3ABC6o+jcKXRjDTg4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uJ4CUV1iru3AnzNtA79biymZMjwlHUzSgyfnsWmqGPjDok6TGCQSj9uC7b3O3oPJJ 7hYekNdQmu7P41mSRVxUZKoW7l4b2DBxXauxvQJ5VcutuHeMtpvZQrN2ZvYFBY8C0w cFwasIhIocEciWso+pgv0fKmhODCmMTdicFt3Zbm+IEEHYWZteSMzg5HUaEWh1wYsS n6woXHFNKHnn6crfiO3t2IWj/U18s5SnVAkRwJYqfkT4yzROMYiHzuA22rvffXunMJ gSApl7UVcU5tNNRz9aag+tq4sRGFtmNYW7vA1PrXzNDpkEpBxiGadFRA0LlgL6wbC/ NAGXWNH4WT4Sw== Date: Sat, 6 May 2023 00:08:22 +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> <20230505233152.GN3223426@dread.disaster.area> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230505233152.GN3223426@dread.disaster.area> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230505_170825_708872_11343929 X-CRM114-Status: GOOD ( 34.12 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Sat, May 06, 2023 at 09:31:52AM +1000, Dave Chinner wrote: > On Fri, May 05, 2023 at 10:47:19PM +0000, Eric Biggers wrote: > > 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. > > Sure it does - what is contained in the field on return is defined > by the result mask. In this case, whatever the filesystem puts in > the DIO fields will match which flag it asserts in the result mask. > > i.e. if the application wants RWF_ATOMIC and so asks for STATX_DIOALIGN | > STATX_DIOALIGN_ATOMIC in the request mask then: > > - if the filesystem does not support RWF_ATOMIC it fills in the > normal DIO alingment values and puts STATX_DIOALIGN in the result > mask. > > Now the application knows that it can't use RWF_ATOMIC, and it > doesn't need to do another statx() call to get the dio alignment > values it needs. > > - if the filesystem supports RWF_ATOMIC, it fills in the values with > the atomic DIO constraints and puts STATX_DIOALIGN_ATOMIC in the > result mask. > > Now the application knows it can use RWF_ATOMIC and has the atomic > DIO constraints in the dio alignment fields returned. > > This uses the request/result masks exactly as intended, yes? > We could certainly implement some scheme like that, but I don't think that was how statx() was intended to work. I think that each bit in the mask was intended to correspond to an independent piece of information. - Eric