linux-kernel - Re: [Linux-nvdimm] [PATCH] pmem: Add prints at module load and unload

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Date:	Thu, 2 Apr 2015 09:01:14 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Boaz Harrosh <boaz@...xistor.com>
Cc:	Christoph Hellwig <hch@....de>,
	linux-nvdimm <linux-nvdimm@...1.01.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [Linux-nvdimm] [PATCH] pmem: Add prints at module load and unload

On Thu, Apr 2, 2015 at 8:47 AM, Boaz Harrosh <boaz@...xistor.com> wrote:
> On 04/02/2015 06:39 PM, Dan Williams wrote:
>> On Thu, Apr 2, 2015 at 8:31 AM, Boaz Harrosh <boaz@...xistor.com> wrote:
>>> Hi Christoph, Ingo
>>>
>>> Please consider this small patch below just a small print at module
>>> load/unload so to know at user systems how things progressed.
>>> As it is now, we know nothing. For any other disk kind we have two
>>> tuns of prints.
>>>
>>> ---
>>> From: Boaz Harrosh <boaz@...xistor.com>
>>> Date: Thu, 2 Apr 2015 16:43:48 +0300
>>> Subject: [PATCH] pmem: Add prints at module load and unload
>>>
>>> When debugging people's systems it is helpful
>>> to see what went on. The load and unload of pmem is
>>> an important event.
>>>
>>> The importance is the number of loaded devices and
>>> error status. The exact device's addresses created
>>> we can see from the other prints at e820 so no need
>>> to duplicate this information.
>>>
>>> While at it fix up a small issue with rw flags.
>>
>> Separate patch for fixes please.
>
> Sigh, OK I was preparing this and hopping it would just
> be SQUASHED into the original patch but Ingo bit me to it
> and already submitted the patches.
>
>>
>>>
>>> Signed-off-by: Boaz Harrosh <boaz@...xistor.com>
>>> ---
>>>  drivers/block/pmem.c | 7 ++++++-
>>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
>>> index 988f384..3f15fbc 100644
>>> --- a/drivers/block/pmem.c
>>> +++ b/drivers/block/pmem.c
>>> @@ -91,8 +91,9 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
>>>  {
>>>         struct pmem_device *pmem = bdev->bd_disk->private_data;
>>>
>>> +       rw &= WRITE;
>>>         pmem_do_bvec(pmem, page, PAGE_CACHE_SIZE, 0, rw, sector);
>>> -       page_endio(page, rw & WRITE, 0);
>>> +       page_endio(page, rw, 0);
>>>
>>>         return 0;
>>>  }
>>> @@ -248,6 +249,9 @@ static int __init pmem_init(void)
>>>         error = platform_driver_register(&pmem_driver);
>>>         if (error)
>>>                 unregister_blkdev(pmem_major, "pmem");
>>> +
>>> +       pr_info("pmem: init %d devices => %d\n",
>>> +               atomic_read(&pmem_index), error);
>>
>> If anything I think these should be dev_dbg().
>
> We do not have a dev at any of this point, and it does not
> belong to any specific device.

Ah, true this is prior to the driver attaching... that said it seems
more relevant to print from probe() (where we do have a device) than
init where the device may remain idle due to some other policy.

> Also I would like this
> _info and not _dbg so to always have it, also for production.
> See the chatter for a single SCSI disk the minimum we need
> is just the small print that tells all that we need (for now)

Not sure we want to follow so closely in the footsteps of SCSI's chattiness.
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