Re: [dm-crypt] Kernel BUG (fs/bio.c:1499) when copying more files to an encrypted device

+cc linux-raid

Mandeep Singh Baines (msb@chromium.org) wrote:

Luzipher McLeod (luziphermcleod@yahoo.ie) wrote:

quoted

Hi Mandeep,

Thanks fpr your quick answer. So, what can be done about this ? Should I try to apply that patch you linked to ? (but I guess a patch from 2007 won't apply cleanly ...)

Hi Luzipher,

I wouldn't apply the patch directly. Just copy bio_multi_split (might
need to do some forward porting) and then modify linear_make_request to
use bio_multi_split instead of bio_split.

But I'm not really an expert on this particular code. I'm hoping someone
else will confirm that this is in fact the bug and not a side effect of
something else. Its seem reasonble that you could get a bio that is
multi-page and falls on a boundary (spans two or more devices). So I
suspect this is the bug.

Regards,
Mandeep

quoted

Regards,
Luzipher

--- On Wed, 25/1/12, Mandeep Singh Baines <msb@chromium.org> wrote:

quoted

From: Mandeep Singh Baines <redacted>
Subject: Re: [dm-crypt] Kernel BUG (fs/bio.c:1499) when copying more files to an encrypted device
To: "Luzipher McLeod" <redacted>
Cc: dm-crypt@saout.de, "NeilBrown" <redacted>
Date: Wednesday, 25 January, 2012, 2:14
Luzipher McLeod (luziphermcleod@yahoo.ie)
wrote:

quoted

Hi :-)

A few days ago I encountered a kernel bug while copying

files to an encrypted filesystem. The specific stack for the
filesystem is: btrfs-on-crypt-on-mdraid. Vasts amounts of
data copied without problems (about 6.3TB with 1.1 TB
remaining), but when copying a certain directory, the kernel
bug surfaces. I repeatedly deleted the affected directory
and tried to re-copy it, but it always fails at the same
point (or close to that). More recent test showed that I
could copy a few more files to the filesystem to a different
directory, but it very quickly failed there as well (a few
megabytes later).

quoted

After talking to the btrfs devs on freenode (as btrfs

is the most experimental thing in the stack, they came to
the conclusion that it's most probably the crypto layer.

quoted

Some details:
gentoo kernel 3.2.1 (custom config and ubuntu config)
mdraid: linear, 4 disks, each 2TB (total 8TB)
crypt: setup via cryptsetup -c aes-xts-plain64 -h plain

-s 512 -d - create tempraid /dev/md/tempraid_lin

quoted

I'd appreciate any help with this and would be happy to

test patches or provide more debug info.

quoted

Thanks and Regards,
Luzipher




The kernel bug output retrieved by netconsole (also at

http://pastebin.com/sjJy7QE4 ):

quoted

    [  294.538422] netconsole:

local port 6666

quoted

    [  333.423583] SysRq :

Changing Loglevel

quoted

    [  333.423609] Loglevel

set to 9

quoted

    [  424.248405]

------------[ cut here ]------------

quoted

    [  424.248447] kernel BUG

at fs/bio.c:1499!

Hi Luzipher,

Looks like the BUG is because bio_split only works on
single-page iovecs.

I see a relevant (old) patch from Neil Brown here:

https://lkml.org/lkml/2007/7/30/496

Regards,
Mandeep

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