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 977C5EB64DC for ; Fri, 21 Jul 2023 16:31:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231757AbjGUQbZ (ORCPT ); Fri, 21 Jul 2023 12:31:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231564AbjGUQbH (ORCPT ); Fri, 21 Jul 2023 12:31:07 -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 DAE9C3AAD; Fri, 21 Jul 2023 09:29:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D795661D19; Fri, 21 Jul 2023 16:28:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 428CBC433C8; Fri, 21 Jul 2023 16:28:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689956888; bh=GrXCeuTWgBbj6biTr+wDYPmdsZ0gc4ne9Z3Z2q6kEWk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=laIiM6VqXLMXUuD21TykYG670dDEsDusDjKmspE0IWxxdtVzV3kfA0PIV+q1vKu5+ KTXxfVmFRY/+f5W4i70hCAREsphJTCMsxkJXpL2t8uxvsCvzXLEnvWkRyBuXCusgvw YEmyLvjYABsuYa44ph2dcBO+JlCHsXTGJRUjjTWHKiB6hk3itjDmflPT/vrXpPrn/7 82I0VLIwTIVfEibmopHPkq52Qk5cQG07Wg9j5ScZBsVGGYiFl1KNJlV9l2kdyqA+eV wxsBo4yb+jfYKQx376mxk/aCN0cGKPSFJmE8/Y88sZHLdB/zQSqZGr+i1oZN+Yq5IF +TS8xXXxPcwlA== Date: Fri, 21 Jul 2023 09:28:07 -0700 From: "Darrick J. Wong" To: Jens Axboe Cc: io-uring@vger.kernel.org, linux-xfs@vger.kernel.org, hch@lst.de, andres@anarazel.de, david@fromorbit.com Subject: Re: [PATCH 6/9] fs: add IOCB flags related to passing back dio completions Message-ID: <20230721162807.GT11352@frogsfrogsfrogs> References: <20230721161650.319414-1-axboe@kernel.dk> <20230721161650.319414-7-axboe@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230721161650.319414-7-axboe@kernel.dk> Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Fri, Jul 21, 2023 at 10:16:47AM -0600, Jens Axboe wrote: > Async dio completions generally happen from hard/soft IRQ context, which > means that users like iomap may need to defer some of the completion > handling to a workqueue. This is less efficient than having the original > issuer handle it, like we do for sync IO, and it adds latency to the > completions. > > Add IOCB_DIO_CALLER_COMP, which the issuer can set if it is able to > safely punt these completions to a safe context. If the dio handler is > aware of this flag, assign a callback handler in kiocb->dio_complete and > associated data io kiocb->private. The issuer will then call this > handler with that data from task context. > > No functional changes in this patch. > > Reviewed-by: Christoph Hellwig > Signed-off-by: Jens Axboe > --- > include/linux/fs.h | 35 +++++++++++++++++++++++++++++++++-- > 1 file changed, 33 insertions(+), 2 deletions(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 6867512907d6..60e2b4ecfc4d 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -338,6 +338,20 @@ enum rw_hint { > #define IOCB_NOIO (1 << 20) > /* can use bio alloc cache */ > #define IOCB_ALLOC_CACHE (1 << 21) > +/* > + * IOCB_DIO_CALLER_COMP can be set by the iocb owner, to indicate that the > + * iocb completion can be passed back to the owner for execution from a safe > + * context rather than needing to be punted through a workqueue.If this If this "...through a workqueue. If this flag is set..." Need a space after the period, and delete one of the "If this". With that fixed, Reviewed-by: Darrick J. Wong --D > + * flag is set, the bio completion handling may set iocb->dio_complete to a > + * handler function and iocb->private to context information for that handler. > + * The issuer should call the handler with that context information from task > + * context to complete the processing of the iocb. Note that while this > + * provides a task context for the dio_complete() callback, it should only be > + * used on the completion side for non-IO generating completions. It's fine to > + * call blocking functions from this callback, but they should not wait for > + * unrelated IO (like cache flushing, new IO generation, etc). > + */ > +#define IOCB_DIO_CALLER_COMP (1 << 22) > > /* for use in trace events */ > #define TRACE_IOCB_STRINGS \ > @@ -351,7 +365,8 @@ enum rw_hint { > { IOCB_WRITE, "WRITE" }, \ > { IOCB_WAITQ, "WAITQ" }, \ > { IOCB_NOIO, "NOIO" }, \ > - { IOCB_ALLOC_CACHE, "ALLOC_CACHE" } > + { IOCB_ALLOC_CACHE, "ALLOC_CACHE" }, \ > + { IOCB_DIO_CALLER_COMP, "CALLER_COMP" } > > struct kiocb { > struct file *ki_filp; > @@ -360,7 +375,23 @@ struct kiocb { > void *private; > int ki_flags; > u16 ki_ioprio; /* See linux/ioprio.h */ > - struct wait_page_queue *ki_waitq; /* for async buffered IO */ > + union { > + /* > + * Only used for async buffered reads, where it denotes the > + * page waitqueue associated with completing the read. Valid > + * IFF IOCB_WAITQ is set. > + */ > + struct wait_page_queue *ki_waitq; > + /* > + * Can be used for O_DIRECT IO, where the completion handling > + * is punted back to the issuer of the IO. May only be set > + * if IOCB_DIO_CALLER_COMP is set by the issuer, and the issuer > + * must then check for presence of this handler when ki_complete > + * is invoked. The data passed in to this handler must be > + * assigned to ->private when dio_complete is assigned. > + */ > + ssize_t (*dio_complete)(void *data); > + }; > }; > > static inline bool is_sync_kiocb(struct kiocb *kiocb) > -- > 2.40.1 >