linux-kernel - Preventing the kernel to perform i/o on plugged in HDD

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Message-ID: <CAPJ9Yc9EFb1E_9t2SwryZWc-gCroEeKrMdRW35k_VGPcBrc2Yg@mail.gmail.com>
Date:   Sat, 3 Sep 2016 21:20:36 +0200
From:   David Balažic <xerces9@...il.com>
To:     linux-kernel@...r.kernel.org
Subject: Preventing the kernel to perform i/o on plugged in HDD

Hi!

I'm trying to rescue some data from a damaged HDD (attached over USB)
and run into the problem that when reading from a damaged part of the
drive, it goes into "panic mode" and refusing access even to good
parts (happened before with other drive).

As the kernel reads the partitioning related sectors at plugin time,
it can trigger this "panic mode" if those sectors are damaged.

I patched my kernel to not read the partitions (a new sysctl that
makes check_partition() just return when set), but it (or something)
still tries to access a few sectors (apparently at the end of the
disk) that again fail.

Question: What access besides partition related is done by the kernel?

Info: Userspace is sysrescd 4.8.1 (I just changed the kernel)

Regards,
David