linux-kernel - Re: Regarding patch "block/blk-mq: Don't complete locally if capacities are different"

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Message-ID: <340f156b-0dbb-45d2-a6dd-31e468ead846@acm.org>
Date: Fri, 23 Aug 2024 07:12:13 -0700
From: Bart Van Assche <bvanassche@....org>
To: MANISH PANDEY <quic_mapa@...cinc.com>,
 Christian Loehle <christian.loehle@....com>,
 Sandeep Dhavale <dhavale@...gle.com>,
 Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Qais Yousef <qyousef@...alina.io>, axboe@...nel.dk, mingo@...nel.org,
 peterz@...radead.org, vincent.guittot@...aro.org,
 linux-block@...r.kernel.org, sudeep.holla@....com,
 Jaegeuk Kim <jaegeuk@...nel.org>, Christoph Hellwig <hch@...radead.org>,
 kailash@...gle.com, tkjos@...gle.com, bvanassche@...gle.com,
 quic_nitirawa@...cinc.com, quic_cang@...cinc.com, quic_rampraka@...cinc.com,
 quic_narepall@...cinc.com,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Regarding patch "block/blk-mq: Don't complete locally if
 capacities are different"

On 8/23/24 6:49 AM, MANISH PANDEY wrote:
> while making the patch, i figured out that queue_flags is unsigned long 
> type and we already reached up to 32 flags as of now.

Really? In Linus' master branch I see 13 queue flags. This is less than
half of 32. From include/linux/blkdev.h:

enum {
	QUEUE_FLAG_DYING,		/* queue being torn down */
	QUEUE_FLAG_NOMERGES,		/* disable merge attempts */
	QUEUE_FLAG_SAME_COMP,		/* complete on same CPU-group */
	QUEUE_FLAG_FAIL_IO,		/* fake timeout */
	QUEUE_FLAG_NOXMERGES,		/* No extended merges */
	QUEUE_FLAG_SAME_FORCE,		/* force complete on same CPU */
	QUEUE_FLAG_INIT_DONE,		/* queue is initialized */
	QUEUE_FLAG_STATS,		/* track IO start and completion times */
	QUEUE_FLAG_REGISTERED,		/* queue has been registered to a disk */
	QUEUE_FLAG_QUIESCED,		/* queue has been quiesced */
	QUEUE_FLAG_RQ_ALLOC_TIME,	/* record rq->alloc_time_ns */
	QUEUE_FLAG_HCTX_ACTIVE,		/* at least one blk-mq hctx is active */
	QUEUE_FLAG_SQ_SCHED,		/* single queue style io dispatch */
	QUEUE_FLAG_MAX
};

Bart.