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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> 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 X-Rspam-User: X-Stat-Signature: kiciiu3fm9kxj8bs9ej9wjzwfciyq5kd X-Rspamd-Queue-Id: 10387100007 X-Rspamd-Server: rspam11 X-HE-Tag: 1723772720-54181 X-HE-Meta: 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 iOHmlQpt 1qEqblwIFgBl6TG/K5oiUagMBD093amj6L7v5SVx2ti7ogwD/veieZfb4acURyXbENzal5aJUPKzY+VoXr23BYZ412q6su1vbqJ/WPisSKjZMa4SE0ednt1UMC0rOb5qE/BCIn3G60Jazhk4jAq1XZfSB15bQsrvzhuVU7NJnjBBtWwrDTDS6GCe/V7cCPOnxWf0bhZS7DXko3/uG0I/9/65CbaSRS4wFTLEEIfBcaNtwOf9//pptgxTs22SQQ9W4qNmbfLP4MBbGeA3pKVYO3t9mBgPm7Syknz+swMeVVZksGpjcyl4rXUqpPRp1LQALN2MuimeZ1job/AdF87KHzMGhIncGCGZ3ixRTU65g+CCjiwHM3MlN2RNwLnYmS/NH/W4iiNR5k6NSfKMn8ify0j569yYdn9KoSFOmjFr0yiTd/FTw2EVZATciaEKhQ6t191ql+DNPUd6eYkCdg9GyBZJwO7HMOAc37EHDingQNdfR3dU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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