linux-kernel - Re: [PATCH A+B] pmem: Add prints at module load and unload

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Date:	Mon, 13 Apr 2015 15:05:27 +0300
From:	Boaz Harrosh <boaz@...xistor.com>
To:	Greg KH <gregkh@...uxfoundation.org>,
	Boaz Harrosh <boaz@...xistor.com>
CC:	Christoph Hellwig <hch@....de>, linux-nvdimm@...1.01.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, axboe@...nel.dk, ross.zwisler@...ux.intel.com
Subject: Re: [PATCH A+B] pmem: Add prints at module load and unload

On 04/13/2015 12:05 PM, Greg KH wrote:
> On Tue, Apr 07, 2015 at 06:46:15PM +0300, Boaz Harrosh wrote:
>> Hi Christoph, Ingo
>>
>> It is important in the lab for postmortem analysis to know if
>> pmem driver loaded and/or unloaded. And the return code from this
>> operation.
>>
>> I submit two versions [A] more chatty and version [B]. Both give me
>> the info I need.
>>
>> I like [B] because [A] prints more lines, and also the driver might not
>> load at the end and we would still not see it from [A]'s prints.
>>
>> But it does not matter that much just take any one you guys like
>> better.
>>
>> Here are the commit logs:
>> ---
>> [PATCH 1A] pmem: Add prints at pmem_probe/remove
>>
>> Add small prints at creation/remove of pmem devices.
>> So we can see in dmesg logs when users loaded/unloaded
>> the pmem driver and what devices were created.
>>
>> The prints will look like this:
>> Printed by e820 on load:
>>  [  +0.000000] user: [mem 0x0000000100000000-0x000000015fffffff] persistent (type 12)
>>  [  +0.000000] user: [mem 0x0000000160000000-0x00000001dfffffff] persistent (type 12)
>>  ...
>> Printed by modprobe pmem:
>>  [  +0.003065] pmem pmem.0.auto: probe [0x0000000100000000:0x60000000]
>>  [  +0.001816] pmem pmem.1.auto: probe [0x0000000160000000:0x80000000]
>>  ...
>> Printed by modprobe -r pmem:
>>  [ +16.299145] pmem pmem.1.auto: remove
>>  [  +0.011155] pmem pmem.0.auto: remove
>>
>> Signed-off-by: Boaz Harrosh <boaz@...xistor.com>
> 
> Don't polute the kernel logs with "chatty" things like this, 

Why do you say this is chatty. With [B] This is a single line of print
on modprobe. With [A] it is a print per device (Is why I like [B])
Compare to all the other block-devices in the system, say scsi, that print
bunch of info for each device, this is very very minimalistic.

> just
> trigger off of the block device uevent if you really want to know if the
> block device is still around or not.
> 

Again I do not need this for run time. At run time I have two tons of ways
to check and see. BTW a uevent is already triggered for insertion as part
of regular block core operation.

I need this at dmesg for when analyzing users logs, say when a crash happens.
I need to see what/when drivers were loaded/unloaded. It is common practice
in dmseg for block devices to leave foot prints.

Sigh, do you not believe that this single line in dmseg makes my life much
easier?

> thanks,
> greg k-h

Thanks
Boaz

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