linux-kernel - RE: [RFC v4 0/3] pstore/rom: new support logger for block devices

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F7D4B623C@ORSMSX110.amr.corp.intel.com>
Date:   Thu, 3 Jan 2019 17:18:49 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     liaoweixiong <liaoweixiong@...winnertech.com>,
        Kees Cook <keescook@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC v4 0/3] pstore/rom: new support logger for block devices

I'm curious why you call this "pstore/rom" rather than the more descriptive "pstore/block".

It looks to be a really good idea.

I think you need to document how the "write" function for the block device must be written.
Since pstore calls this at "panic" time, the write path:

+ Cannot allocate any memory
+ Must be polled, not interrupt driven
+ Cannot take any locks that may be held by regular code
+ ... perhaps other restrictions that I can't think of right now

The memory allocation restriction is likely easy to get around. Just allocate anything
you need at pstore "init" time rather than waiting until the panic.

-Tony