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Subject: Re: [PATCH v12 2/4] pstore/blk: add blkoops for pstore_blk
To:     liaoweixiong <liaoweixiong@allwinnertech.com>,
        Kees Cook <keescook@chromium.org>,
        Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>,
        Tony Luck <tony.luck@intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Arnd Bergmann <arnd@arndb.de>, Rob Herring <robh@kernel.org>
Cc:     linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <1551337948-16451-1-git-send-email-liaoweixiong@allwinnertech.com>
 <1551337948-16451-3-git-send-email-liaoweixiong@allwinnertech.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <21827ba0-1c89-c16e-0d64-0a508eeae915@infradead.org>
Date:   Tue, 5 Mar 2019 17:14:09 -0800
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Hi,

On 2/27/19 11:12 PM, liaoweixiong wrote:
> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
> index defcb75..7dfe00b 100644
> --- a/fs/pstore/Kconfig
> +++ b/fs/pstore/Kconfig
> @@ -160,3 +160,117 @@ config PSTORE_BLK
>  	help
>  	  This enables panic and oops message to be logged to a block dev
>  	  where it can be read back at some later point.
> +
> +config PSTORE_BLKOOPS
> +	tristate "pstore block with oops logger"
> +	depends on PSTORE_BLK
> +	help
> +	  This is a sample for pstore block with oops logger.
> +
> +	  It CANNOT record panic log as no read/write apis for panic registered.

	                                              APIs

> +
> +	  It CAN record oops log even power failure if
> +	  "PSTORE_BLKOOPS_BLKDEV" on Kconfig or "block-device" on dts or
> +	  "blkdev" on module parameter is valid.
> +
> +	  Otherwise, it can only record data to ram buffer, which will be
> +	  dropped when reboot.

	  dropped on reboot.
or
	  dropped when rebooting.

> +
> +	  NOTE that, there are three ways to set parameters of blkoops and
> +	  prioritize according to configuration flexibility. That is
> +	  Kconfig < device tree < module parameters. It means that the value can
> +	  be overwritten by higher priority settings.
> +	  1. Kconfig
> +	     It	just sets a default value.
> +	  2. device tree
> +	     It is set on device tree, which will overwrites value from Kconfig,

	                                          overwrite the value from Kconfig,

> +	     but can also be overwritten by module parameters.
> +	  3. module parameters
> +	     It is the first priority. Take care of that blkoops will take lower
> +	     priority settings if higher priority one do not set.
> +
> +config PSTORE_BLKOOPS_DMESG_SIZE
> +	int "dmesg size in kbytes for blkoops"
> +	depends on PSTORE_BLKOOPS
> +	default 64
> +	help
> +	  This just sets size of dmesg (dmesg_size) for pstore/blk. The value
> +	  must be a multiple of 4096.
> +
> +	  NOTE that, there are three ways to set parameters of blkoops and
> +	  prioritize according to configuration flexibility. That is
> +	  Kconfig < device tree < module parameters. It means that the value can
> +	  be overwritten by higher priority settings.
> +	  1. Kconfig
> +	     It	just sets a default value.
> +	  2. device tree
> +	     It is set on device tree, which will overwrites value from Kconfig,

	                                          overwrite the value from Kconfig,

> +	     but can also be overwritten by module parameters.
> +	  3. module parameters
> +	     It is the first priority. Take care of that blkoops will take lower
> +	     priority settings if higher priority one do not set.
> +
> +config PSTORE_BLKOOPS_TOTAL_SIZE
> +	int "total size in kbytes for blkoops"
> +	depends on PSTORE_BLKOOPS
> +	default 0
> +	help
> +	  The total size in kbytes pstore/blk can use. It must be less than or
> +	  equal to size of block device if @blkdev valid. If @total_size is zero
> +	  with @blkdev, @total_size will be set to equal to size of @blkdev.

	                                    set equal to size of @blkdev.

> +	  The value must be a multiple of 4096.
> +
> +	  NOTE that, there are three ways to set parameters of blkoops and
> +	  prioritize according to configuration flexibility. That is
> +	  Kconfig < device tree < module parameters. It means that the value can
> +	  be overwritten by higher priority settings.
> +	  1. Kconfig
> +	     It	just sets a default value.
> +	  2. device tree
> +	     It is set on device tree, which will overwrites value from Kconfig,

	                                          overwrite the value from Kconfig,

> +	     but can also be overwritten by module parameters.
> +	  3. module parameters
> +	     It is the first priority. Take care of that blkoops will take lower
> +	     priority settings if higher priority one do not set.
> +
> +config PSTORE_BLKOOPS_BLKDEV
> +	string "block device for blkoops"
> +	depends on PSTORE_BLKOOPS
> +	default ""
> +	help
> +	  This just sets block device (blkdev) for pstore/blk. Pstore/blk
> +	  will record data to this block device to avoid losing data due to
> +	  power failure. So, If it is not set, pstore/blk will drop all data

	                     if

> +	  when reboot.

	  on reboot.

> +
> +	  It accpet the following variants:

	     accepts

> +	  1) <hex_major><hex_minor> device number in hexadecimal represents
> +	     itself no leading 0x, for example b302.
> +	  2) /dev/<disk_name> represents the device number of disk
> +	  3) /dev/<disk_name><decimal> represents the device number
> +	     of partition - device number of disk plus the partition number
> +	  4) /dev/<disk_name>p<decimal> - same as the above, that form is

	                                              above; this form is

> +	     used when disk name of partitioned disk ends on a digit.

	                                             ends with a digit.

> +	  5) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
> +	     unique id of a partition if the partition table provides it.
> +	     The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
> +	     partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
> +	     filled hex representation of the 32-bit "NT disk signature", and PP
> +	     is a zero-filled hex representation of the 1-based partition number.
> +	  6) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation
> +	     to a partition with a known unique id.
> +	  7) <major>:<minor> major and minor number of the device separated by
> +	     a colon.
> +
> +	  NOTE that, there are three ways to set parameters of blkoops and
> +	  prioritize according to configuration flexibility. That is
> +	  Kconfig < device tree < module parameters. It means that the value can
> +	  be overwritten by higher priority settings.
> +	  1. Kconfig
> +	     It	just sets a default value.
> +	  2. device tree
> +	     It is set on device tree, which will overwrites value from Kconfig,

	                                          overwrite the value from Kconfig,

> +	     but can also be overwritten by module parameters.
> +	  3. module parameters
> +	     It is the first priority. Take care of that blkoops will take lower
> +	     priority settings if higher priority one do not set.


-- 
~Randy