Re: [PATCH v2] scsi: core: Fix sbitmap depth in scsi_realloc_sdev_budget_map()

From: Damien Le Moal <damien.lemoal@opensource.wdc.com>
To: John Garry <john.garry@huawei.com>,
	jejb@linux.ibm.com, martin.petersen@oracle.com
Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
	bvanassche@acm.org, martin.wilck@suse.com, ming.lei@redhat.com,
	hch@lst.de, hare@suse.de
Subject: Re: [PATCH v2] scsi: core: Fix sbitmap depth in scsi_realloc_sdev_budget_map()
Date: Wed, 16 Mar 2022 20:38:18 +0900	[thread overview]
Message-ID: <9768fa36-27ed-834f-0462-3b79fd8b3478@opensource.wdc.com> (raw)
In-Reply-To: <1647423870-143867-1-git-send-email-john.garry@huawei.com>

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@huawei.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.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@opensource.wdc.com>

-- 
Damien Le Moal
Western Digital Research