WARNING: quotas may be inconsistent, rescan needed

WARNING: quotas may be inconsistent, rescan needed

[Suman Chakravartula]

Hello my dear upstream heroes,

We are using progs v4.4.1 and kernel 4.4.5 in Rockstor and sometimes
this warning is displayed while assigning a qgroup. Here's a sample
output.

/sbin/btrfs qgroup assign 0/408 2015/6 /mnt2/<btrfs_pool>
WARNING: quotas may be inconsistent, rescan needed

2015/6 is the qgroup of a subvolume(/mnt2/<btrfs_name>/<subvol_name>)
created much earlier.

This started happening since progs v4.2. There are three scenarios I've tested.

1. Just ignore the warning and check if the qgroup assignment
succeeded with a "qgroup show" command. In most cases, the assignment
shows up immediately. But it could take a bit in some cases. Is there
any self/auto consistency check that is triggered by default? If so
can someone explain how that works?

2. Add a --rescan option to to the "qgroup assign" command above to
auto schedule a rescan as per the man page. Is this safe to do? What
are pros and cons?

3. Execute a "quata rescan" separately if the warning is displayed. Is
this any different from (2)?

Thanks for reading!

-- 
Suman Chakravartula
Founder @ Rockstor

http://rockstor.com
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