Hello Theodore,

Very interesting response, thank you! It all makes sense. And I realise
it's hard to make everyone happy yes.

On 21-05-2020 16:48, Theodore Y. Ts'o wrote:
> 
> In *general* things are mostly safe unless you need to do an
> overlapping move of the inode table, in which case it is very hard to
> make it be 100% safe.
> 
Interesting too. And this may be in line with what I ended up
experimenting with! Indeed I later realised I could just create LVM
snapshots and e2fsck them: Always came out clean, while saying
"filesystem with errors, check required".

Of course I don't know whether data *integrity* was correct, but I
presume that's "easy" to guarantee if everything's sequenced properly.

That testing was all during the pass 2 block relocations. Which I guess
is also the least risky pass then?

> If you would like to help, you could try running resize2fs -p on a
> test file system, and then try to randomly interrupt the resize at
> various points, and then run e2fsck -fy and during which phase of the
> resize you see things getting corrupted.
> 
So I've tried the above 6×, and never managed to get it to report
corruption, which is a great outcome as well!

Pass 3 I didn't spot in time, and these were the only passes actually
reported by the progress indicator.

> It's not a high priority for me, since I have way too many other
> things to worry about, if it is high priority for *you*, some
> contributions to the effort would be much appreciated.  After all,
> Open source means you get to help fix the things you care about.  :-)
> 
Hah, for sure. It's not super important to me either and I think it's
hard to do anything that *will* help some people while not being a
backward incompatible change to others.

Just like I presume telling people that interrupting is "probably" a
safe thing to do during block relocation is risky for the next time
someone does that and things *do* go wrong.

However, with tools like this I always wonder why the progress indicator
isn't on by default, and maybe in resize2fs' case a backward compatible
change, and similar to dd, would be to enable the progress indicator on
SIGUSR1?


Kind regards,

Wilmer v/d Gaast.

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