Re: [PATCH v8 01/11] pstore/zone: Introduce common layer to manage storage zones

From: WeiXiong Liao <liaoweixiong@allwinnertech.com>
To: Kees Cook <keescook@chromium.org>
Cc: Anton Vorontsov <anton@enomsg.org>,
	Colin Cross <ccross@android.com>, Tony Luck <tony.luck@intel.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Rob Herring <robh@kernel.org>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mtd@lists.infradead.org
Subject: Re: [PATCH v8 01/11] pstore/zone: Introduce common layer to manage storage zones
Date: Tue, 12 May 2020 13:47:56 +0800	[thread overview]
Message-ID: <57efa2b5-d598-a600-5f74-8fd81299fc58@allwinnertech.com> (raw)
In-Reply-To: <202005112212.2E75B83@keescook>

hi Kees Cook,

On 2020/5/12 PM 1:15, Kees Cook wrote:
> On Tue, May 12, 2020 at 11:55:20AM +0800, WeiXiong Liao wrote:
>> On 2020/5/12 AM 7:32, Kees Cook wrote:
>>> [...]
>>> +struct psz_context {
>>> +	struct pstore_zone **kpszs;
>>> +	unsigned int kmsg_max_cnt;
>>> +	unsigned int kmsg_read_cnt;
>>> +	unsigned int kmsg_write_cnt;
>>> +	/*
>>> +	 * These counters should be calculated during recovery.
>>> +	 * It records the oops/panic times after crashes rather than boots.
>>> +	 */
>>> +	unsigned int oops_counter;
>>> +	unsigned int panic_counter;
>>
>> oops/panic_counter is designed to count the crash times since the
>> linux kernel was installed. pstore/zone lookup the max counter from all
>> valid kmsg zones when recovery and saves them to oops/panic_counter.
>> However, they are unable to get real number if we remove files. It's
>> not serious, we can fix it after this series.
> 
> Since the kernel was installed? I don't see a kernel version check in
> here? Or do you mean "since ever", in that it's a rolling count?
> 

Yes, "since ever".

>> And since pstore supports "max_reason", should pstore/zone count for
>> other reason?
> 
> For now, no. I opted to try to keep this as simple as possible a port
> from dump_oops to max_reason for now.
> 

OK.

>>> +static inline int psz_kmsg_erase(struct psz_context *cxt,
>>> +		struct pstore_zone *zone, struct pstore_record *record)
>>> +{
>>> +	struct psz_buffer *buffer = zone->buffer;
>>> +	struct psz_kmsg_header *hdr =
>>> +		(struct psz_kmsg_header *)buffer->data;
>>> +
>>> +	if (unlikely(!psz_ok(zone)))
>>> +		return 0;
>>> +	/* this zone is already updated, no need to erase */
>>> +	if (record->count != hdr->counter)
>>> +		return 0;
>>
>> These codes is to fix bug that user remove files on pstore filesystem
>> but kmsg zone is already updated and pstore/zone should not erase
>> zone. It work for oops and panic because the count number is increasing.
>> However, it's useless for other reason of kmsg. We can fix it after this
>> series.
> 
> Okay, sounds good.
> 

-- 
WeiXiong Liao