linux-kernel - Re: [Outreachy kernel] [PATCH v3] staging: unisys: visorhba: Convert module from IDR to XArray

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Message-ID: <20210426192101.GQ235567@casper.infradead.org>
Date:   Mon, 26 Apr 2021 20:21:01 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     outreachy-kernel@...glegroups.com, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        David Kershner <david.kershner@...sys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [Outreachy kernel] [PATCH v3] staging: unisys: visorhba: Convert
 module from IDR to XArray

On Mon, Apr 26, 2021 at 08:42:45PM +0200, Fabio M. De Francesco wrote:
> +static void setup_scsitaskmgmt_handles(struct xarray *xa, struct uiscmdrsp *cmdrsp,
>  				       wait_queue_head_t *event, int *result)
>  {
> -	/* specify the event that has to be triggered when this */
> -	/* cmd is complete */
> -	cmdrsp->scsitaskmgmt.notify_handle =
> -		simple_idr_get(idrtable, event, lock);
> -	cmdrsp->scsitaskmgmt.notifyresult_handle =
> -		simple_idr_get(idrtable, result, lock);
> +	u32 id;
> +	int ret;
> +
> +	/* specify the event that has to be triggered when this cmd is complete */
> +	id = (u32)cmdrsp->scsitaskmgmt.notify_handle;
> +	ret = xa_alloc_irq(xa, &id, event, XA_LIMIT(1, INT_MAX), GFP_KERNEL);

OK, think this one through a bit.  When xa_alloc_irq() stores the ID that
it assigned into 'id', what happens to it next?

> +	id = (u32)cmdrsp->scsitaskmgmt.notifyresult_handle;
> +	ret = xa_alloc_irq(xa, &id, result, XA_LIMIT(1, INT_MAX), GFP_KERNEL);
>  }

> @@ -1053,8 +1018,6 @@ static int visorhba_probe(struct visor_device *dev)
>  	if (err)
>  		goto err_debugfs_info;
>  
> -	idr_init(&devdata->idr);

You still need to initialise the XArray, either with xa_init() or by
using DEFINE_XARRAY.  Since it's dynamically allocated, the former is
correct.