linux-kernel - RE: [PATCH v2 3/3] efi: Add support for using efivars as a pstore backend

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Date:	Tue, 7 Jun 2011 13:16:55 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Matthew Garrett <mjg@...hat.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Matt_Domsch@...l.com" <Matt_Domsch@...l.com>
Subject: RE: [PATCH v2 3/3] efi: Add support for using efivars as a pstore
 backend

+	efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
+	if (efi_pstore_info.buf) {
+		efi_pstore_info.bufsize = 1024;
+		efi_pstore_info.data = efivars;
+		mutex_init(&efi_pstore_info.buf_mutex);
+		pstore_register(&efi_pstore_info);
+	}

I'd imagined #ifdef CONFIG_PSTORE around this (and the
efi_pstore_info definition) rather than providing stubs
for the !PSTORE case.

But your way works too.

You should avoid a memory leak with:

		if (!pstore_register(&efi_pstore_info))
			kfree(efi_pstore_info.buf);

I've also been thinking some more about how to handle a
system that has more than one pstore back-end available.
I still don't have any good ideas how to make use of more
than one backend - but it occurs to me that we may need
a way to let the user choose which to use (e.g. in the
unlikely event that a BIOS bug made one of ERST or EFI
unusable by pstore). The current "whoever registers first
gets to use it" now seems inadequate.

Perhaps a command line "pstore={backend}" might work, so
the user could specify pstore=efi to get your code, and
pstore=erst to get mine.

-Tony
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