linux-kernel - Re: [PATCH v3 1/2] blk-mq: fix elevator depth

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <98b30bef-3f7c-411b-b724-ed614a86b056@linux.ibm.com>
Date: Thu, 21 Aug 2025 17:51:46 +0530
From: Nilay Shroff <nilay@...ux.ibm.com>
To: Yu Kuai <yukuai1@...weicloud.com>, yukuai3@...wei.com, axboe@...nel.dk,
        bvanassche@....org, ming.lei@...hat.com, hare@...e.de
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com
Subject: Re: [PATCH v3 1/2] blk-mq: fix elevator depth_updated method



On 8/21/25 11:36 AM, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Current depth_updated has some problems:
> 
> 1) depth_updated() will be called for each hctx, while all elevators
> will update async_depth for the disk level, this is not related to hctx;
> 2) In blk_mq_update_nr_requests(), if previous hctx update succeed and
> this hctx update failed, q->nr_requests will not be updated, while
> async_depth is already updated with new nr_reqeuests in previous
> depth_updated();
> 3) All elevators are using q->nr_requests to calculate async_depth now,
> however, q->nr_requests is still the old value when depth_updated() is
> called from blk_mq_update_nr_requests();
> 
> Those problems are first from error path, then mq-deadline, and recently
> for bfq and kyber, fix those problems by:
> 
> - pass in request_queue instead of hctx;
> - move depth_updated() after q->nr_requests is updated in
>   blk_mq_update_nr_requests();
> - add depth_updated() call inside init_sched() method to initialize
>   async_depth;
> - remove init_hctx() method for mq-deadline and bfq that is useless now;
> 
> Fixes: 77f1e0a52d26 ("bfq: update internal depth state when queue depth changes")
> Fixes: 39823b47bbd4 ("block/mq-deadline: Fix the tag reservation code")
> Fixes: 42e6c6ce03fd ("lib/sbitmap: convert shallow_depth from one word to the whole sbitmap")
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Looks good to me:
Reviewed-by: Nilay Shroff <nilay@...ux.ibm.com>