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From: Qu Wenruo <>
To: Pierre Abbat <>,
Subject: Re: Trying to mount hangs
Date: Fri, 22 May 2020 18:02:44 +0800
Message-ID: <> (raw)
In-Reply-To: <2582603.WkyslYimHe@puma>

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On 2020/5/22 下午5:40, Pierre Abbat wrote:
> On Thursday, May 21, 2020 9:32:54 PM EDT Qu Wenruo wrote:
>> Considering your btrfs check reports no serious problem, the hang looks
>> strange.
>> The remaining possibility is the log tree.
>> You could try to boot using any liveCD with new enough kernel, then
>> btrfs ins dump-super <device> | grep log_root
> I can do that booted normally from the M.2. The output is
> log_root                862339072
> log_root_transid        0
> log_root_level          0

So indeed log tree is involved.

>> If the result is not 0, then try btrfs rescue zero-log, then try mount
>> again.
> You seem to be misunderstanding me. I'm not trying to fix the broken filesystem; 
> I already recovered the files to a new drive. I'm trying to give you enough 
> information to reproduce the hang in mount, so that you can fix the bug. If I 
> have to copy the entire filesystem to an external drive and ship it, I'll do 
> that, but I'm hoping that some smaller amount of data that I can upload in a 
> few hours would be sufficient.

For that purpose, we have btrfs-image, which will only dump the
metadata, which is way smaller than the full disk, and can be further
compressed using -c9 option. (And you can compress it furthermore).

That btrfs-image dump even contains log tree, which is exactly what we
need to fix the hang.


> When I write a function that reads a file of a certain format, unless it's a 
> static file like a list of all primes less than 65536 with associated data, I 
> fuzz it so that, if it's given a file that's not exactly in that format, it 
> won't hang or crash.
> Pierre

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  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21  1:34 Pierre Abbat
2020-05-21  7:56 ` Qu Wenruo
2020-05-21 23:48   ` Pierre Abbat
2020-05-22  1:32     ` Qu Wenruo
2020-05-22  9:40       ` Pierre Abbat
2020-05-22 10:02         ` Qu Wenruo [this message]
2020-05-24  6:37           ` Pierre Abbat
2020-05-24  9:24             ` Qu Wenruo
2020-05-24 12:10               ` Pierre Abbat
2020-05-24 12:32                 ` Qu Wenruo
2020-05-27 10:41 ` Qu Wenruo

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