[LU-19564] return OS_STATFS_ENOSPC if MDT changelog is (nearly) full

• Type: Improvement
• Resolution: Unresolved
• Priority: Medium
• Affects Version/s: Lustre 2.17.0
• Severity: 3
• Assignee: WC Triage
• Reporter: Andreas Dilger

Description

If the MDT changelog is full (exceeded the (LLOG_BITMAP_BYTES * 8 = 64768)^2 record limit) and changelog garbage collection (GC) is disabled (meaning that the inactive changelog consumer will not be deregistered), then it makes sense for the MDT to set the OS_STATFS_ENOSPC flag in the MDS_STATFS reply to the clients.

That will at least give clients some hint that the MDT is unusable when they are checking MDTs for space balance and they should redirect new subdirectory creation to a different MDT that might not be having this problem, until such a time that the changelog consumer is fixed and starts consuming records again.

The clients should already handle OS_STATFS_ENOSPC to shift subdirectory creation to other MDTs, but this flag is currently only set if the MDT has no more free blocks. This unfortunately does not affect new file creation today, only new subdirectories.

Issue Links

• is related to: LU-18022 DNE3: client to retry on other MDT if mkdir returns EDQUOT
• is related to: LU-10784 DNE3: mkdir() automatically create remote directory on MDS which has more space