From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C8CE1D69E for ; Fri, 16 Aug 2024 01:45:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723772725; cv=none; b=r0BsQ/0nrzb4i9GrGlUmnxgmTiQdCRprFKiB6LlZVd44xDinDqGogOX4hsTGyBCSnpef6XVq5Ag7zn6G6cfI96elgATZYW0xEtCd19lbDBoNvbK6EmGvF+wPM+pYomuH0nF/u6TjgEeSEBK2bo738iPIA19psDcPCAKrLmkHQj4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723772725; c=relaxed/simple; bh=s/nwH08NlRsAyxnKAea0guN+gj5xC4Yb7Z1jzGw+MO0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HKWSYy/TjbVnkHDXaO+uCHNfutQQ6owLxdRP4Qo+gs+o1dhy6hQEsN8ZYsRDsAyNw6CogLV4ba845VOek1kWYwFYfOh44QVWZ7u3Ga3WmPqE80DYCYy3+CEI/delT/GfNXfqYbQLEZlCEFPhSSUIKEGfkk7xoo0lWZq1nud0RUI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=SCkveOxM; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SCkveOxM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723772722; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Mxy0rtdNdtcD3NoIzzm3sQ/N1TTdvcPBZq39L7HnMHg=; b=SCkveOxM4GRa0bFugW84OdROG6kYCkev7SAzN5fxP0m4/ElokLI61eX35SfQdqyfafoIXg PczNo6QrBlFNDnjLrj4HH+p4ByB8yVoMPVWRqd3+ZzGIjJgfAqtRheE7IedEt7uD68K3XY UBGd9LDTg5his7L7Zmq5Oo+J4k+m7EM= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-253-Uz1QAaw1Ni6II1qQQ0QGBQ-1; Thu, 15 Aug 2024 21:45:18 -0400 X-MC-Unique: Uz1QAaw1Ni6II1qQQ0QGBQ-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6E4FD1955D52; Fri, 16 Aug 2024 01:45:17 +0000 (UTC) Received: from fedora (unknown [10.72.116.112]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5FD6C19560AA; Fri, 16 Aug 2024 01:45:11 +0000 (UTC) Date: Fri, 16 Aug 2024 09:45:06 +0800 From: Ming Lei To: Jens Axboe Cc: Pavel Begunkov , io-uring@vger.kernel.org, Conrad Meyer , linux-block@vger.kernel.org, linux-mm@kvack.org, ming.lei@redhat.com Subject: Re: [RFC 5/5] block: implement io_uring discard cmd Message-ID: References: <6ecd7ab3386f63f1656dc766c1b5b038ff5353c2.1723601134.git.asml.silence@gmail.com> <4d016a30-d258-4d0e-b3bc-18bf0bd48e32@kernel.dk> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d016a30-d258-4d0e-b3bc-18bf0bd48e32@kernel.dk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On Thu, Aug 15, 2024 at 07:24:16PM -0600, Jens Axboe wrote: > On 8/15/24 5:44 PM, Ming Lei wrote: > > On Thu, Aug 15, 2024 at 06:11:13PM +0100, Pavel Begunkov wrote: > >> On 8/15/24 15:33, Jens Axboe wrote: > >>> On 8/14/24 7:42 PM, Ming Lei wrote: > >>>> On Wed, Aug 14, 2024 at 6:46?PM Pavel Begunkov wrote: > >>>>> > >>>>> Add ->uring_cmd callback for block device files and use it to implement > >>>>> asynchronous discard. Normally, it first tries to execute the command > >>>>> from non-blocking context, which we limit to a single bio because > >>>>> otherwise one of sub-bios may need to wait for other bios, and we don't > >>>>> want to deal with partial IO. If non-blocking attempt fails, we'll retry > >>>>> it in a blocking context. > >>>>> > >>>>> Suggested-by: Conrad Meyer > >>>>> Signed-off-by: Pavel Begunkov > >>>>> --- > >>>>> block/blk.h | 1 + > >>>>> block/fops.c | 2 + > >>>>> block/ioctl.c | 94 +++++++++++++++++++++++++++++++++++++++++ > >>>>> include/uapi/linux/fs.h | 2 + > >>>>> 4 files changed, 99 insertions(+) > >>>>> > >>>>> diff --git a/block/blk.h b/block/blk.h > >>>>> index e180863f918b..5178c5ba6852 100644 > >>>>> --- a/block/blk.h > >>>>> +++ b/block/blk.h > >>>>> @@ -571,6 +571,7 @@ blk_mode_t file_to_blk_mode(struct file *file); > >>>>> int truncate_bdev_range(struct block_device *bdev, blk_mode_t mode, > >>>>> loff_t lstart, loff_t lend); > >>>>> long blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg); > >>>>> +int blkdev_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags); > >>>>> long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg); > >>>>> > >>>>> extern const struct address_space_operations def_blk_aops; > >>>>> diff --git a/block/fops.c b/block/fops.c > >>>>> index 9825c1713a49..8154b10b5abf 100644 > >>>>> --- a/block/fops.c > >>>>> +++ b/block/fops.c > >>>>> @@ -17,6 +17,7 @@ > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> +#include > >>>>> #include "blk.h" > >>>>> > >>>>> static inline struct inode *bdev_file_inode(struct file *file) > >>>>> @@ -873,6 +874,7 @@ const struct file_operations def_blk_fops = { > >>>>> .splice_read = filemap_splice_read, > >>>>> .splice_write = iter_file_splice_write, > >>>>> .fallocate = blkdev_fallocate, > >>>>> + .uring_cmd = blkdev_uring_cmd, > >>>> > >>>> Just be curious, we have IORING_OP_FALLOCATE already for sending > >>>> discard to block device, why is .uring_cmd added for this purpose? > >> > >> Which is a good question, I haven't thought about it, but I tend to > >> agree with Jens. Because vfs_fallocate is created synchronous > >> IORING_OP_FALLOCATE is slow for anything but pretty large requests. > >> Probably can be patched up, which would involve changing the > >> fops->fallocate protot, but I'm not sure async there makes sense > >> outside of bdev (?), and cmd approach is simpler, can be made > >> somewhat more efficient (1 less layer in the way), and it's not > >> really something completely new since we have it in ioctl. > > > > Yeah, we have ioctl(DISCARD), which acquires filemap_invalidate_lock, > > same with blkdev_fallocate(). > > > > But this patch drops this exclusive lock, so it becomes async friendly, > > but may cause stale page cache. However, if the lock is required, it can't > > be efficient anymore and io-wq may be inevitable, :-) > > If you want to grab the lock, you can still opportunistically grab it. > For (by far) the common case, you'll get it, and you can still do it > inline. If the lock is grabbed in the whole cmd lifetime, it is basically one sync interface cause there is at most one async discard cmd in-flight for each device. Meantime the handling has to move to io-wq for avoiding to block current context, the interface becomes same with IORING_OP_FALLOCATE? thanks, Ming