[LU-6951] sanity test_27m: @@@@@@ FAIL: OST0 was full but new created file still use it

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.13.0
• Affects Version/s: Lustre 2.8.0

Epic/Theme

test

• Severity: 3
• Assignee: Andrew Perepechko
• Reporter: Andrew Perepechko

Description

sanity 27m fails with "OST0 was full but new created file still use it"
if this test runs with more than 1 connected client. A simple reproducer
is "MOUNT_2=true REFORMAT=true ONLY=27m bash sanity.sh".

The reason seems to be grants. In my setup, every client initially
gets 2 Mb grant which never shrinks to 0. When dd from the first
client receives ENOSPC, it does not really mean the OST is filled up,
since the client is not allowed to use other clients' grants. When
creating a new file, the MDS still sees free space on OST0 equal to
the amount of unused grants and allocates new objects on OST0.
Eventually, the test reports failure.

It's not clear if it's a defect in Lustre or it's a test defect and
clients # > 1 case should be skipped. We would like to know your
opinion. Thanks.

Issue Links

• is related to: LU-3859 grant shrinker floods OST and produce a large load