linux-kernel - Re: [PATCH v4 10/25] nvdimm: Add driver for OpenCAPI Persistent Memory

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Message-ID: <20200329025617.GT22483@bombadil.infradead.org>
Date:   Sat, 28 Mar 2020 19:56:17 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Alastair D'Silva <alastair@...ilva.org>
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Cédric Le Goater <clg@...d.org>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kurz <groug@...d.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org
Subject: Re: [PATCH v4 10/25] nvdimm: Add driver for OpenCAPI Persistent
 Memory

On Fri, Mar 27, 2020 at 06:11:47PM +1100, Alastair D'Silva wrote:
> +static struct mutex minors_idr_lock;
> +static struct idr minors_idr;
...
> +	mutex_lock(&minors_idr_lock);
> +	minor = idr_alloc(&minors_idr, ocxlpmem, 0, NUM_MINORS, GFP_KERNEL);
> +	mutex_unlock(&minors_idr_lock);
...
> +	mutex_lock(&minors_idr_lock);
> +	idr_remove(&minors_idr, MINOR(ocxlpmem->dev.devt));
> +	mutex_unlock(&minors_idr_lock);
...
> +	mutex_init(&minors_idr_lock);
> +	idr_init(&minors_idr);

Unless you look up ocxlpmem by minor number later in the patch series (and
most of the series didn't make it to my mailbox), this can just be an ida.

static DEFINE_IDA(minors);
...
minor = ida_alloc_max(&minors, NUM_MINORS, GFP_KERNEL);
...
ida_free(&minors, MINOR(ocxlpmem->dev.devt));
...
and you can drop the dynamic initialisation.  And the mutex.