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

mpenttil
2022-03-11T03:31:16Z

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

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()
--
2.17.1