linux-ext4 - [Bug 25832] kernel crashes when a mounted ext3/4 file system is physically removed

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Date:	Sat, 23 Apr 2011 00:32:35 GMT
From:	bugzilla-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 25832] kernel crashes when a mounted ext3/4 file system is
 physically removed

https://bugzilla.kernel.org/show_bug.cgi?id=25832

--- Comment #65 from rocko <rockorequin@...mail.com>  2011-04-23 00:32:32 ---
Yes, the crash only happens when I'm running a desktop (gdm in this case),
partly because this is what handles the auto-mounting of the USB drives. I
suppose we *could* tell people to just not use a desktop at all :)

I don't think users deliberately yank out mounted USB drives. I think the most
likely real-world scenarios that trigger this crash are (1) suspend, remove
drive, resume [ie how I first noticed this], (2) remove the wrong drive by
accident, (3) a power failure makes the drive suddenly go offline [I've seen
that, too].

Anyway, my test crash case using the script above that was working so reliably
for this ext4 USB key is no longer crashing the kernel in either 2.6.38.3 or
2.6.39-rc4 (I've done over a thousand bind/unbind cycles for each now). My
guess is that the suspend/resume test results in a higher likelihood of I/O
(especially if multiple drives are involved) and therefore triggering the bug.

I'm also still curious whether it's possible for the ext3/4 drive to somehow
get its format into a state that causes this to happen, given that yesterday it
crashed so reliably but not today. If so, couldn't it be possible that such a
state could be corrected by a fsck and therefore reduce the chances of this
mystery I/O pattern happening?

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