linux-kernel - RE: [PATCH v2 3/5] efi_pstore: Remove a logic erasing entries from a write callback to hold multiple logs

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Message-ID: <A5ED84D3BB3A384992CBB9C77DEDA4D413889905@USINDEM103.corp.hds.com>
Date:	Thu, 25 Oct 2012 20:51:06 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Mike Waychison <mikew@...gle.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: RE: [PATCH v2 3/5] efi_pstore: Remove a logic erasing entries from
 a write callback to hold multiple logs

> So doesn't this break erasing of existing dumps in pstore-efivars?
> Unless efi_pstore_read still understands the older variable name formats, users will be stranded with dumps consuming space in
> efivars that aren't exported via pstore anymore.

Patch 2/5, 3/5 and 4/5 don't change an existing format of a variable name and don't break anything.
The existing format consists of type, id and ctime. And it is not moditied by these patches.
Here is a variable name (and guid) of efi_pstore in curret linus-tree.

	ls /sys/firmware/efi/vars/
	dump-type0-1-1351113059-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0
	dump-type0-2-1351113059-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0
	dump-type0-3-1351113059-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0

	Variable Name: dump-type0-1-1351113059
	GUID: cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0

On the other hand, patch 5/5 changes the format by adding sequence counter.
But efi_pstore_read is modied to work correctly in it.

	dump-type0-1-1-1351113059-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0

	Variable Name: dump-type0-1-1-1351113059
	GUID: cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0

If I need to elaborate more, please feel free to ask me:)
I'm not sure if I understand your question completely.

Seiji

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