linux-kernel - Re: [PATCH v2] scsi: core: Fix sbitmap depth in scsi_realloc_sdev_budget

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Message-ID: <9768fa36-27ed-834f-0462-3b79fd8b3478@opensource.wdc.com>
Date:   Wed, 16 Mar 2022 20:38:18 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     John Garry <john.garry@...wei.com>, jejb@...ux.ibm.com,
        martin.petersen@...cle.com
Cc:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        bvanassche@....org, martin.wilck@...e.com, ming.lei@...hat.com,
        hch@....de, hare@...e.de
Subject: Re: [PATCH v2] scsi: core: Fix sbitmap depth in
 scsi_realloc_sdev_budget_map()

On 3/16/22 18:44, John Garry wrote:
> In commit edb854a3680b ("scsi: core: Reallocate device's budget map on
> queue depth change"), the sbitmap for the device budget map may be
> reallocated after the slave device depth is configured.
> 
> When the sbitmap is reallocated we use the result from
> scsi_device_max_queue_depth() for the sbitmap size, but don't resize to
> match the actual device queue depth.
> 
> Fix by resizing the sbitmap after reallocating the budget sbitmap. We do
> this instead of init'ing the sbitmap to the device queue depth as the user
> may want to change the queue depth later via sysfs or other.
> 
> Fixes: edb854a3680b ("scsi: core: Reallocate device's budget map on queue depth change")
> Signed-off-by: John Garry <john.garry@...wei.com>
> Reviewed-by: Ming Lei <ming.lei@...hat.com>
> ---
> Changes since v1 (apart from sending as a separate patch):
> - Add fixes and RB tag (thanks)
> - mention in commit message why we don't init sbitmap at queue depth
> 
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index f4e6c68ac99e..2ef78083f1ef 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -223,6 +223,8 @@ static int scsi_realloc_sdev_budget_map(struct scsi_device *sdev,
>  	int ret;
>  	struct sbitmap sb_backup;
>  
> +	depth = min_t(unsigned int, depth, scsi_device_max_queue_depth(sdev));
> +
>  	/*
>  	 * realloc if new shift is calculated, which is caused by setting
>  	 * up one new default queue depth after calling ->slave_configure
> @@ -245,6 +247,9 @@ static int scsi_realloc_sdev_budget_map(struct scsi_device *sdev,
>  				scsi_device_max_queue_depth(sdev),
>  				new_shift, GFP_KERNEL,
>  				sdev->request_queue->node, false, true);
> +	if (!ret)
> +		sbitmap_resize(&sdev->budget_map, depth);
> +
>  	if (need_free) {
>  		if (ret)
>  			sdev->budget_map = sb_backup;

Tested-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>

-- 
Damien Le Moal
Western Digital Research