linux-ext4 - Re: Help! How to delete an 8094-byte PATH?

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Date:   Thu, 27 Jan 2022 17:50:39 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Maxim Blinov <maxim.blinov@...ecosm.com>
Cc:     linux-ext4@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: Help! How to delete an 8094-byte PATH?

cc'ing linux-fsdevel too.

On 22/01/27 07:06AM, Maxim Blinov wrote:
> Hi all,
>
> I'm not a subscriber to this list (so please put me in the CC), but I've
> hit a really annoying un-googleable issue that I don't know who to ask
> about.
>
> A runaway script has been recursively creating sub-directories under
> sub-directories until it hit the (apparent) OS limit. The path in
> question goes something like this:
>
> /work/build-native/binutils-gdb/gnulib/confdir3/confdir3/confdir3/confdir3/confdir3/........
> (you get the idea)
>
> It was only stopped by the following error:
> mkdir: cannot create directory 'confdir3': File name too long
>
> OK, fine, that was silly but whatever, right? I tried to delete this
> huge directory from the top with

;)

>
> rm -rf confdir3/
>
> but that simply generated the same error as above. So, I figured "Hey,

Strange. Though I didn't try creating same name subdirectories like how you have
done above i.e. confdir3 within confdir3 and recurse.
But I was able to remove the parent directory after hitting the max PATH_LEN
issue.

I ran this test below test to see if it fails on my ext4 latest tree. But this
passes. https://github.com/pjd/pjdfstest/blob/master/tests/mkdir/03.t

But just curious, by any chance did below fixes it for you?
echo 3 > /proc/sys/vm/drop_caches


-ritesh

> I'll just walk all the way to the bottom, and delete the directories
> one-by-one bottom up". Here's the script I ran to get to the bottom:
>
> $ for i in $(seq 999999); do echo "im $i levels deep"; cd confdir3; done;
>
> It then ran for a while, and eventually I got to the bottom:
>
> ```
> ...
> im 892 levels deep
> im 893 levels deep
> im 894 levels deep
> im 895 levels deep
> im 896 levels deep
> bash: cd: confdir3: File name too long
> $ ls
> <nothing here>
> ```
>
> So then, I `cd ../`, and `rmdir confdir3`, but even here, I get
>
> rmdir: failed to remove 'confdir3/': File name too long
>
> I would be very grateful if someone could please help suggest how I
> might get this infernal tower of directories off of my precious ext4
> partition.
>
> I was thinking maybe there's some kind of magic "forget this directory
> inode ever existed" command, but I am out of my depth with filesystems.
>
> Best Regards,
>
> Maxim Blinov