linux-kernel - Re: [PATCH v3] mm/hmm/test: use char dev with struct device to get device node

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Date:   Mon, 21 Mar 2022 04:57:03 +0200
From:   Mika Penttilä <mpenttil@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     apopple@...dia.com, jhubbard@...dia.com, rcampbell@...dia.com,
        jgg@...pe.ca, vbabka@...e.cz
Subject: Re: [PATCH v3] mm/hmm/test: use char dev with struct device to get
 device node

Sorry ignore this one, see v4


On 21.3.2022 4.44, mpenttil@...hat.com wrote:
> From: Mika Penttilä <mpenttil@...hat.com>
> 
> HMM selftests use an in-kernel pseudo device to emulate device private
> memory. The pseudo device registers a major device range for two pseudo
> device instances. User space has a script that reads /proc/devices in
> order to find the assigned major number, and sends that to mknod(1),
> once for each node.
> 
> This duplicates a fair amount of boilerplate that misc device can do
> instead.
> 
> Change this to use misc device, which makes the device node names appear
> for us. This also enables udev-like processing if desired.
> 
> Delete the /proc/devices parsing from the user-space test script, now
> that it is unnecessary.
> 
> Signed-off-by: Mika Penttilä <mpenttil@...hat.com>
> Cc: Alistair Popple <apopple@...dia.com>
> Cc: John Hubbard <jhubbard@...dia.com>
> Cc: Ralph Campbell <rcampbell@...dia.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> ---
> v3:
>          - use cdev_device_add() instead of miscdevice
> v2:
>          - Cleanups per review comments from John Hubbard
>          - Added Tested-by and Ccs
> 
>   lib/test_hmm.c                         | 25 ++++++++++++++++++-------
>   tools/testing/selftests/vm/test_hmm.sh |  6 ------
>   2 files changed, 18 insertions(+), 13 deletions(-)
> 
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index 767538089a62..d247e9c0fe94 100644
> --- a/lib/test_hmm.c
> +++ b/lib/test_hmm.c
> @@ -29,11 +29,17 @@
>   
>   #include "test_hmm_uapi.h"
>   
> -#define DMIRROR_NDEVICES		2
>   #define DMIRROR_RANGE_FAULT_TIMEOUT	1000
>   #define DEVMEM_CHUNK_SIZE		(256 * 1024 * 1024U)
>   #define DEVMEM_CHUNKS_RESERVE		16
>   
> +static const char *dmirror_device_names[] = {
> +	"hmm_dmirror0",
> +	"hmm_dmirror1"
> +};
> +
> +#define DMIRROR_NDEVICES ARRAY_SIZE(dmirror_device_names)
> +
>   static const struct dev_pagemap_ops dmirror_devmem_ops;
>   static const struct mmu_interval_notifier_ops dmirror_min_ops;
>   static dev_t dmirror_dev;
> @@ -74,7 +80,7 @@ struct dmirror {
>    * ZONE_DEVICE pages for migration and simulating device memory.
>    */
>   struct dmirror_chunk {
> -	struct dev_pagemap	pagemap;
> +	struct dev_pagemap      pagemap;
>   	struct dmirror_device	*mdevice;
>   };
>   
> @@ -82,8 +88,9 @@ struct dmirror_chunk {
>    * Per device data.
>    */
>   struct dmirror_device {
> -	struct cdev		cdevice;
> -	struct hmm_devmem	*devmem;
> +	struct cdev             cdevice;
> +	struct device           device;
> +	struct hmm_devmem       *devmem;
>   
>   	unsigned int		devmem_capacity;
>   	unsigned int		devmem_count;
> @@ -132,7 +139,7 @@ static int dmirror_fops_open(struct inode *inode, struct file *filp)
>   	xa_init(&dmirror->pt);
>   
>   	ret = mmu_interval_notifier_insert(&dmirror->notifier, current->mm,
> -				0, ULONG_MAX & PAGE_MASK, &dmirror_min_ops);
> +					0, ULONG_MAX & PAGE_MASK, &dmirror_min_ops);
>   	if (ret) {
>   		kfree(dmirror);
>   		return ret;
> @@ -1225,7 +1232,11 @@ static int dmirror_device_init(struct dmirror_device *mdevice, int id)
>   
>   	cdev_init(&mdevice->cdevice, &dmirror_fops);
>   	mdevice->cdevice.owner = THIS_MODULE;
> -	ret = cdev_add(&mdevice->cdevice, dev, 1);
> +	device_initialize(&mdevice->device);
> +	dev_set_name(&mdevice->device, "%s", dmirror_device_names[id]);
> +	mdevice->device.devt = dev;
> +
> +	ret = cdev_device_add(&mdevice->cdevice, &mdevice->device);
>   	if (ret)
>   		return ret;
>   
> @@ -1252,7 +1263,7 @@ static void dmirror_device_remove(struct dmirror_device *mdevice)
>   		kfree(mdevice->devmem_chunks);
>   	}
>   
> -	cdev_del(&mdevice->cdevice);
> +	cdev_device_del(&mdevice->cdevice, &mdevice->device);
>   }
>   
>   static int __init hmm_dmirror_init(void)
> diff --git a/tools/testing/selftests/vm/test_hmm.sh b/tools/testing/selftests/vm/test_hmm.sh
> index 0647b525a625..69f5889f8575 100755
> --- a/tools/testing/selftests/vm/test_hmm.sh
> +++ b/tools/testing/selftests/vm/test_hmm.sh
> @@ -41,17 +41,11 @@ check_test_requirements()
>   load_driver()
>   {
>   	modprobe $DRIVER > /dev/null 2>&1
> -	if [ $? == 0 ]; then
> -		major=$(awk "\$2==\"HMM_DMIRROR\" {print \$1}" /proc/devices)
> -		mknod /dev/hmm_dmirror0 c $major 0
> -		mknod /dev/hmm_dmirror1 c $major 1
> -	fi
>   }
>   
>   unload_driver()
>   {
>   	modprobe -r $DRIVER > /dev/null 2>&1
> -	rm -f /dev/hmm_dmirror?
>   }
>   
>   run_smoke()