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Subject: Re: [PATCH v4 6/6] powerpc/fadump: sysfs for fadump memory
 reservation
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     mpe@ellerman.id.au, mahesh@linux.vnet.ibm.com,
        hbathini@linux.ibm.com, linux-kernel@vger.kernel.org,
        linuxppc-dev@ozlabs.org, corbet@lwn.net, linux-doc@vger.kernel.org
References: <20191206122434.29587-1-sourabhjain@linux.ibm.com>
 <20191206122434.29587-7-sourabhjain@linux.ibm.com>
 <20191206124855.GE1360047@kroah.com>
From:   Sourabh Jain <sourabhjain@linux.ibm.com>
Date:   Sat, 7 Dec 2019 00:49:33 +0530
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On 12/6/19 6:18 PM, Greg KH wrote:
> On Fri, Dec 06, 2019 at 05:54:34PM +0530, Sourabh Jain wrote:
>> Add a sys interface to allow querying the memory reserved by FADump for
>> saving the crash dump.
>>
>> Also added Documentation/ABI for the new sysfs file.
>>
>> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>> ---
>>  Documentation/ABI/testing/sysfs-kernel-fadump    |  7 +++++++
>>  Documentation/powerpc/firmware-assisted-dump.rst |  5 +++++
>>  arch/powerpc/kernel/fadump.c                     | 15 +++++++++++++++
>>  3 files changed, 27 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-kernel-fadump b/Documentation/ABI/testing/sysfs-kernel-fadump
>> index 5d988b919e81..8f7a64a81783 100644
>> --- a/Documentation/ABI/testing/sysfs-kernel-fadump
>> +++ b/Documentation/ABI/testing/sysfs-kernel-fadump
>> @@ -31,3 +31,10 @@ Description:	write only
>>  		the system is booted to capture the vmcore using FADump.
>>  		It is used to release the memory reserved by FADump to
>>  		save the crash dump.
>> +
>> +What:		/sys/kernel/fadump/mem_reserved
>> +Date:		Dec 2019
>> +Contact:	linuxppc-dev@lists.ozlabs.org
>> +Description:	read only
>> +		Provide information about the amount of memory reserved by
>> +		FADump to save the crash dump in bytes.
>> diff --git a/Documentation/powerpc/firmware-assisted-dump.rst b/Documentation/powerpc/firmware-assisted-dump.rst
>> index 365c10209ef3..04993eaf3113 100644
>> --- a/Documentation/powerpc/firmware-assisted-dump.rst
>> +++ b/Documentation/powerpc/firmware-assisted-dump.rst
>> @@ -268,6 +268,11 @@ Here is the list of files under kernel sysfs:
>>      be handled and vmcore will not be captured. This interface can be
>>      easily integrated with kdump service start/stop.
>>  
>> + /sys/kernel/fadump/mem_reserved
>> +
>> +   This is used to display the memory reserved by FADump for saving the
>> +   crash dump.
>> +
>>   /sys/kernel/fadump_release_mem
>>      This file is available only when FADump is active during
>>      second kernel. This is used to release the reserved memory
>> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
>> index 41a3cda81791..b2af51b7c750 100644
>> --- a/arch/powerpc/kernel/fadump.c
>> +++ b/arch/powerpc/kernel/fadump.c
>> @@ -1357,6 +1357,13 @@ static ssize_t fadump_enabled_show(struct kobject *kobj,
>>  	return sprintf(buf, "%d\n", fw_dump.fadump_enabled);
>>  }
>>  
>> +static ssize_t fadump_mem_reserved_show(struct kobject *kobj,
>> +					struct kobj_attribute *attr,
>> +					char *buf)
>> +{
>> +	return sprintf(buf, "%ld\n", fw_dump.reserve_dump_area_size);
>> +}
>> +
>>  static ssize_t fadump_register_show(struct kobject *kobj,
>>  					struct kobj_attribute *attr,
>>  					char *buf)
>> @@ -1430,6 +1437,10 @@ static struct kobj_attribute enable_attr = __ATTR(enabled,
>>  static struct kobj_attribute register_attr = __ATTR(registered,
>>  						0644, fadump_register_show,
>>  						fadump_register_store);
>> +static struct kobj_attribute mem_reserved_attr = __ATTR(mem_reserved,
>> +						0444, fadump_mem_reserved_show,
>> +						NULL);
> 
> __ATTRI_RO()?
> 
>> +
>>  
>>  DEFINE_SHOW_ATTRIBUTE(fadump_region);
>>  
>> @@ -1464,6 +1475,10 @@ static void fadump_init_files(void)
>>  			pr_err("unable to create release_mem sysfs file (%d)\n",
>>  			       rc);
>>  	}
>> +	rc = sysfs_create_file(fadump_kobj, &mem_reserved_attr.attr);
>> +	if (rc)
>> +		pr_err("unable to create mem_reserved sysfs file (%d)\n",
>> +		       rc);
> 
> Again, put it in an attribute group, that would have only required one
> line, and not this mess of not cleaning up if something went wrong.


Will make the changes accordingly.


Thanks,
Sourabh Jain