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Message-ID: <f36ae290-979e-1f6f-3169-edd5f729a971@redhat.com>
Date: Thu, 10 Mar 2022 07:33:50 +0200
From: Mika Penttilä <mpenttil@...hat.com>
To: John Hubbard <jhubbard@...dia.com>,
Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Cc: Jérôme Glisse <jglisse@...hat.com>,
Alistair Popple <apopple@...dia.com>,
Ralph Campbell <rcampbell@...dia.com>,
Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH] HMM selftests changes
On 10.3.2022 5.44, John Hubbard wrote:
> On 3/8/22 5:10 AM, Vlastimil Babka wrote:
>> +CC relevant folks
>>
>> On 3/8/22 02:57, mpenttil@...hat.com wrote:
>>> From: Mika Penttilä <mpenttil@...hat.com>
>
> Hi Mika,
>
> This looks like a very nice cleanup and simplification, delighted to see
> it!
Thanks!
>
> In fact, I like it so much that I've got a bunch of fussy nitpicks I'm
> hoping you'll consider applying, below. :)
>
> Also, I'm assuming you've tested it a little bit? (My test rig is boxed
> up for another day or two, don't ask...haha.)
>
Yes it passed the tests with the changes.
>>>
>>> HMM selftests use a in-kernel pseudo device to emulate device private memory.
>>>
>>> For now, the pseudo device registers a major device range for two pseudo device instances.
>>> User space has a script that goes figures out from /proc/devices the assigned major
>>> and mknods the device nodes.
>>>
>>> Change this use to a more standard device framework, like misc device,
>>> which makes the device node names to appear right under any decent user space.
>>> This also makes it possible for udev- like processing if wanted,
>>> and the /proc/devices parsing is not needed any more.
>
> How about this for the subject line and body? I've made the subject line
> match what other commits look like in this area, and I've clarified the
> wording in the body:
>
>
> mm/hmm/test: simplify hmm test code: use miscdevice instead of char dev
>
> 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>
>>> ---
>>> lib/test_hmm.c | 46 +++++++++++++++-----------
>>> tools/testing/selftests/vm/test_hmm.sh | 6 ----
>>> 2 files changed, 26 insertions(+), 26 deletions(-)
>>>
>>> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
>>> index 767538089a62..76f6129e1f1f 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 +24,25 @@
>>> #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
>>>
>>> +
>
> Extra newline, please delete.
>
yep
>>> +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 +88,7 @@ struct dmirror_chunk {
>>> * Per device data.
>>> */
>>> struct dmirror_device {
>>> - struct cdev cdevice;
>>> + struct miscdevice miscdevice;
>>> struct hmm_devmem *devmem;
>>>
>>> unsigned int devmem_capacity;
>>> @@ -118,16 +124,20 @@ 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_device *dd = container_of(filp->private_data,
>>> + struct dmirror_device, miscdevice
>>> + );
>
> Let's delete that whole chunk, because the variable is unnecessary, and
> is adding to the line count and mental load for no reason.
Agreed.
>
> Look how much cleaner this it gets after applying this incremental diff
> on top of your patch:
>
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index 76f6129e1f1f..3ec8ca8059cd 100644
> --- a/lib/test_hmm.c
> +++ b/lib/test_hmm.c
> @@ -125,19 +125,16 @@ static void dmirror_bounce_fini(struct dmirror_bounce *bounce)
> static int dmirror_fops_open(struct inode *inode, struct file *filp)
> {
>
> - struct dmirror_device *dd = container_of(filp->private_data,
> - struct dmirror_device, miscdevice
> - );
> struct dmirror *dmirror;
> int ret;
>
> -
> /* Mirror this process address space */
> dmirror = kzalloc(sizeof(*dmirror), GFP_KERNEL);
> if (dmirror == NULL)
> return -ENOMEM;
>
> - dmirror->mdevice = dd;
> + dmirror->mdevice = container_of(filp->private_data,struct dmirror_device,
> + miscdevice);
> mutex_init(&dmirror->mutex);
> xa_init(&dmirror->pt);
>
>
>>> struct dmirror *dmirror;
>>> int ret;
>>>
>>> +
>>> /* Mirror this process address space */
>>> dmirror = kzalloc(sizeof(*dmirror), GFP_KERNEL);
>>> if (dmirror == NULL)
>>> return -ENOMEM;
>>>
>>> - dmirror->mdevice = container_of(cdev, struct dmirror_device, cdevice);
>>> + dmirror->mdevice = dd;
>>> mutex_init(&dmirror->mutex);
>>> xa_init(&dmirror->pt);
>>>
>>> @@ -1216,16 +1226,18 @@ 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 +1264,7 @@ 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 +1272,6 @@ 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 +1284,7 @@ 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 +1294,7 @@ 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);
>>> +
>
> Another extra newline, please delete it.
yes
>
>>> }
>>>
>>> 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?
>
> Nice!
>
>>> }
>>>
>>> run_smoke()
>>
>
> thanks,
Ok will make the changes and repost,
thanks!
--Mika
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