Re: [PATCH v2] mm/hmm/test: simplify hmm test code: use miscdevice instead of char dev

John Hubbard
2022-03-11T06:15:12Z

On 3/10/22 19:30, mpenttil@redhat.com wrote:
> From: Mika Penttilä <mpenttil@redhat.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.
>
> v2:
> - Cleanups per review comments from John Hubbard
> - Added Tested-by and Ccs

The three lines above, starting with "v2:", belong after the "---". That
way, they are not included in the commit log. That's the convention.

I think Andrew can fix it up for you, no need to spin a new patch for
that.

Anyway, this looks good now, so please feel free to add:

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
--
John Hubbard
NVIDIA

>
> Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
> Tested-by: Alistair Popple <apopple@nvidia.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Ralph Campbell <rcampbell@nvidia.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> ---
> lib/test_hmm.c | 40 ++++++++++++--------------
> tools/testing/selftests/vm/test_hmm.sh | 6 ----
> 2 files changed, 19 insertions(+), 27 deletions(-)
>
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index 767538089a62..0e1488e1bad8 100644
> --- a/lib/test_hmm.c
> +++ b/lib/test_hmm.c
> @@ -10,7 +10,6 @@
> #include <linux/mm.h>
> #include <linux/module.h>
> #include <linux/kernel.h>
> -#include <linux/cdev.h>
> #include <linux/device.h>
> #include <linux/mutex.h>
> #include <linux/rwsem.h>
> @@ -25,18 +24,24 @@
> #include <linux/swapops.h>
> #include <linux/sched/mm.h>
> #include <linux/platform_device.h>
> +#include <linux/miscdevice.h>
> #include <linux/rmap.h>
>
> #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;
>
> struct dmirror_device;
>
> @@ -82,7 +87,7 @@ struct dmirror_chunk {
> * Per device data.
> */
> struct dmirror_device {
> - struct cdev cdevice;
> + struct miscdevice miscdevice;
> struct hmm_devmem *devmem;
>
> unsigned int devmem_capacity;
> @@ -118,7 +123,6 @@ static void dmirror_bounce_fini(struct dmirror_bounce *bounce)
>
> static int dmirror_fops_open(struct inode *inode, struct file *filp)
> {
> - struct cdev *cdev = inode->i_cdev;
> struct dmirror *dmirror;
> int ret;
>
> @@ -127,12 +131,13 @@ static int dmirror_fops_open(struct inode *inode, struct file *filp)
> if (dmirror == NULL)
> return -ENOMEM;
>
> - dmirror->mdevice = container_of(cdev, struct dmirror_device, cdevice);
> + dmirror->mdevice = container_of(filp->private_data,
> + struct dmirror_device, miscdevice);
> mutex_init(&dmirror->mutex);
> 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;
> @@ -1216,16 +1221,16 @@ static const struct dev_pagemap_ops dmirror_devmem_ops = {
>
> static int dmirror_device_init(struct dmirror_device *mdevice, int id)
> {
> - dev_t dev;
> int ret;
>
> - dev = MKDEV(MAJOR(dmirror_dev), id);
> mutex_init(&mdevice->devmem_lock);
> spin_lock_init(&mdevice->lock);
>
> - cdev_init(&mdevice->cdevice, &dmirror_fops);
> - mdevice->cdevice.owner = THIS_MODULE;
> - ret = cdev_add(&mdevice->cdevice, dev, 1);
> + mdevice->miscdevice.minor = MISC_DYNAMIC_MINOR;
> + mdevice->miscdevice.name = dmirror_device_names[id];
> + mdevice->miscdevice.fops = &dmirror_fops;
> +
> + ret = misc_register(&mdevice->miscdevice);
> if (ret)
> return ret;
>
> @@ -1252,7 +1257,7 @@ static void dmirror_device_remove(struct dmirror_device *mdevice)
> kfree(mdevice->devmem_chunks);
> }
>
> - cdev_del(&mdevice->cdevice);
> + misc_deregister(&mdevice->miscdevice);
> }
>
> static int __init hmm_dmirror_init(void)
> @@ -1260,11 +1265,6 @@ static int __init hmm_dmirror_init(void)
> int ret;
> int id;
>
> - ret = alloc_chrdev_region(&dmirror_dev, 0, DMIRROR_NDEVICES,
> - "HMM_DMIRROR");
> - if (ret)
> - goto err_unreg;
> -
> for (id = 0; id < DMIRROR_NDEVICES; id++) {
> ret = dmirror_device_init(dmirror_devices + id, id);
> if (ret)
> @@ -1277,8 +1277,7 @@ static int __init hmm_dmirror_init(void)
> err_chrdev:
> while (--id >= 0)
> dmirror_device_remove(dmirror_devices + id);
> - unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
> -err_unreg:
> +
> return ret;
> }
>
> @@ -1288,7 +1287,6 @@ static void __exit hmm_dmirror_exit(void)
>
> for (id = 0; id < DMIRROR_NDEVICES; id++)
> dmirror_device_remove(dmirror_devices + id);
> - unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
> }
>
> module_init(hmm_dmirror_init);
> 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()