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From: james harvey <jamespharvey20@gmail.com>
To: dsterba@suse.cz, Qu Wenruo <wqu@suse.com>,
	Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH] btrfs: inode: Don't compress if NODATASUM or NODATACOW set
Date: Mon, 14 May 2018 18:29:22 -0400	[thread overview]
Message-ID: <CA+X5Wn4tv=h5xt2D5wMb7mFm3SuWG0efahuyFwdTGgTkeYhnmA@mail.gmail.com> (raw)
In-Reply-To: <20180514165205.GP6649@twin.jikos.cz>

On Mon, May 14, 2018 at 12:52 PM, David Sterba <dsterba@suse.cz> wrote:
> On Mon, May 14, 2018 at 03:02:10PM +0800, Qu Wenruo wrote:
>> As btrfs(5) specified:
>>
>>       Note
>>       If nodatacow or nodatasum are enabled, compression is disabled.
>>
>> If NODATASUM or NODATACOW set, we should not compress the extent.
>>
>> And in fact, we have bug report about corrupted compressed extent
>> leading to memory corruption in mail list.
>
> Link please.

https://bugzilla.kernel.org/show_bug.cgi?id=199707
&
https://www.spinics.net/lists/linux-btrfs/msg77971.html

>> Although it's mostly buggy lzo implementation causing the problem, btrfs
>> still needs to be fixed to meet the specification.
>
> That's very vague, what's the LZO bug? If the input is garbage and lzo
> decompression cannot decompress it, it's not a lzo bug.

The bug is the kernel doesn't just give an I/O error.  It totally
crashes the system.  Even a regular user cat'ing an invalid
btrfs-lzo-compressed file will take the system down.  Qu's current
theory which I agree with is it causes some kind of random kernel
memory corruption.  The crashes sometimes include "BTRFS: decompress
failed" at the start, but give backtraces for other things than btrfs
lzo code.

  parent reply	other threads:[~2018-05-14 22:29 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-14  7:02 [PATCH] btrfs: inode: Don't compress if NODATASUM or NODATACOW set Qu Wenruo
2018-05-14  8:10 ` Nikolay Borisov
2018-05-14  8:20   ` Roman Mamedov
2018-05-14  8:36     ` Nikolay Borisov
2018-05-14  9:31       ` james harvey
2018-05-14  9:39       ` Roman Mamedov
2018-05-14  9:46         ` Nikolay Borisov
2018-05-14 16:49           ` David Sterba
2018-05-14  9:30     ` james harvey
2018-05-14 10:35       ` Qu Wenruo
2018-05-14 22:24         ` james harvey
2018-05-15  0:15         ` james harvey
2018-05-14  8:24   ` Qu Wenruo
2018-05-14 16:52 ` David Sterba
2018-05-14 20:46   ` Timofey Titovets
2018-05-15 18:18     ` David Sterba
2018-05-14 22:29   ` james harvey [this message]
2018-05-15  1:35   ` Qu Wenruo

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