Check tmp free space before start extraction

[donob4n]

Tries to fix QubesOS/qubes-issues#4791

I think that the problem could be more complex if the destination pool is on the same device of the temporary directory.

Also I am not sure if all the data is being extracted before deleting anything, according to my recent experience it seems the case but looking at the code I am not sure about this.

Well at least I think this does not hurt and it prevents to extract a lot of gigabytes for just failing after some hours.

[codecov]

Codecov Report

Merging #101 into master will increase coverage by 0.16%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master     #101      +/-   ##
==========================================
+ Coverage   74.75%   74.92%   +0.16%     
==========================================
  Files          47       47              
  Lines        5677     5682       +5     
==========================================
+ Hits         4244     4257      +13     
+ Misses       1433     1425       -8

Impacted Files	Coverage Δ
qubesadmin/backup/restore.py	57.52% <80%> (+0.1%)	⬆️
qubesadmin/tools/qvm_run.py	79.76% <0%> (+2.97%)	⬆️
qubesadmin/spinner.py	77.41% <0%> (+6.45%)	⬆️

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[marmarek]

Also I am not sure if all the data is being extracted before deleting anything

What do you mean deleting?

[donob4n]

What do you mean deleting?

I mean removing unneeded (already restored) temporary files. I am not sure if

qubes-core-admin-client/qubesadmin/backup/restore.py

Line 706 in 769f8a5

os.remove(filename)

it is being executed for some temp files before the whole process ends.

In that case the free space restriction could be lowered, but if the temporary directory and the current pool are on the same device it should be hardened.

Do you known exactly when the temporary files are deleted?

[marmarek]

it is being executed for some temp files before the whole process ends.

Yes, it's deleted as soon as the content is imported into the volume. Ideally (when decrypt, decompress and import is fast enough) there should be only a need for a single chunk of data (about 100MB). But in practice the opposite is true.

There are some ideas how to solve it without requiring disk space for the whole backup:
QubesOS/qubes-issues#3230 (comment)

[donob4n]

Well, seeing that the space problem is not a real requirement I am closing this.

I will try to test with the "checkpoint" method.