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

From: Luzipher McLeod <redacted>
Subject: Re: [dm-crypt] Kernel BUG (fs/bio.c:1499) when copying more files to an encrypted device
To: "Mandeep Singh Baines" <redacted>
Cc: dm-crypt@saout.de, linux-raid@vger.kernel.org
Date: Monday, 30 January, 2012, 0:46
Hi Mandeep,

sorry for the long delay, I couldn't get around to try this
earlier.
I did as you suggested and copied the bio_multi_split
function into bio.c, and added its signature to bio.h (as
done by the original patch by Neil Brown). Then I replaced
the call to bio_split with bio_multi_split in
linear_make_request.
Unfortunately I fail with the forward-porting. Compilation
results in:

fs/bio.c: In function 'bio_multi_split':
fs/bio.c:1585:23: error: 'struct bio' has no member named
'bi_iocnt'
fs/bio.c:1591:8: error: 'struct bio' has no member named
'bi_offset'
fs/bio.c:1592:15: error: 'struct bio' has no member named
'bi_offset'
fs/bio.c:1593:5: error: 'struct bio' has no member named
'bi_offset'
fs/bio.c:1598:12: error: 'struct bio' has no member named
'bi_offset'
make[1]: *** [fs/bio.o] Error 1
make: *** [fs] Error 2

Further examination reveals, that 'struct bio', as defined
in blk_types.h really doesn't have those members anymore and
I can't determine an easy replacement for those. The whole
original patch also doesn't touch 'struct bio', so I'm at a
loss what to do.

Thanks for any pointers or hints how to resolve this !

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

quoted

To: "Mandeep Singh Baines" <redacted>
Cc: "Luzipher McLeod" <redacted>,

dm-crypt@saout.de,
linux-raid@vger.kernel.org

quoted

Date: Wednesday, 25 January, 2012, 23:46
+cc linux-raid

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

quoted

Luzipher McLeod (luziphermcleod@yahoo.ie)

wrote:

quoted

quoted

Hi Mandeep,

Thanks fpr your quick answer. So, what can be

done

quoted

about this ? Should I try to apply that patch you

linked to

quoted

? (but I guess a patch from 2007 won't apply cleanly

...)

quoted

quoted

quoted

Hi Luzipher,

I wouldn't apply the patch directly. Just copy

bio_multi_split (might

quoted

need to do some forward porting) and then modify

linear_make_request to

quoted

use bio_multi_split instead of bio_split.

But I'm not really an expert on this particular

code.

quoted

I'm hoping someone

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else will confirm that this is in fact the bug and

not

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a side effect of

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something else. Its seem reasonble that you could

get a

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bio that is

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multi-page and falls on a boundary (spans two or

more

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devices). So I

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suspect this is the bug.

Regards,
Mandeep

quoted

Regards,
Luzipher

--- On Wed, 25/1/12, Mandeep Singh Baines

[off-list ref]

quoted

wrote:

quoted

quoted

quoted

From: Mandeep Singh Baines <redacted>
Subject: Re: [dm-crypt] Kernel BUG

(fs/bio.c:1499) when copying more files to an

encrypted

quoted

device

quoted

quoted

quoted

To: "Luzipher McLeod" <redacted>
Cc: dm-crypt@saout.de,

"NeilBrown" [off-list ref]

quoted

quoted

quoted

Date: Wednesday, 25 January, 2012, 2:14
Luzipher McLeod (luziphermcleod@yahoo.ie)
wrote:

quoted

Hi :-)

A few days ago I encountered a

kernel

quoted

bug while copying

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files to an encrypted filesystem. The

specific stack for the

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quoted

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filesystem is:

btrfs-on-crypt-on-mdraid.

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Vasts amounts of

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data copied without problems (about

6.3TB

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with 1.1 TB

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remaining), but when copying a certain

directory, the kernel

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bug surfaces. I repeatedly deleted the

affected directory

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and tried to re-copy it, but it always

fails

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at the same

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point (or close to that). More recent

test

quoted

showed that I

quoted

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could copy a few more files to the

filesystem

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to a different

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quoted

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directory, but it very quickly failed

there

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as well (a few

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megabytes later).

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After talking to the btrfs devs on

freenode (as btrfs

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quoted

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is the most experimental thing in the

stack,

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they came to

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the conclusion that it's most probably

the

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crypto layer.

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Some details:
gentoo kernel 3.2.1 (custom config

and

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ubuntu config)

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mdraid: linear, 4 disks, each 2TB

(total

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8TB)

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crypt: setup via cryptsetup -c

aes-xts-plain64 -h plain

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-s 512 -d - create tempraid

/dev/md/tempraid_lin

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quoted

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I'd appreciate any help with this

and

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would be happy to

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test patches or provide more debug

info.

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quoted

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Thanks and Regards,
Luzipher




The kernel bug output retrieved by

netconsole (also at

quoted

quoted

quoted

http://pastebin.com/sjJy7QE4 ):

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    [  294.538422]

netconsole:

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local port 6666

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    [  333.423583] SysRq :

Changing Loglevel

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    [  333.423609] Loglevel

set to 9

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    [  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

quoted

works on

quoted

quoted

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single-page iovecs.

I see a relevant (old) patch from Neil

Brown

quoted

here:

quoted

quoted

quoted

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

Regards,
Mandeep

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