[LU-18860] Unlink does not set properly CLF_UNLINK_LAST changelog flag

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.17.0
• Labels: LTS15
• Severity: 3
• Assignee: Etienne Aujames
• Reporter: Etienne Aujames

Description

Lustre should emit a CL_UNLINK changelog with CLF_UNLINK_LAST flag if the last link of a file is removed. But if the file is open on a client, this is not happening.
This confuses the robinhood changelog reader: it does not remove the inode entry in the database for that case.

Working case

[root@dev lustre]# lfs changelog_clear lustre-MDT0000 cl1 0
[root@dev lustre]# lfs changelog lustre-MDT0000                                                                        
[root@dev lustre]# 
[root@dev lustre]# touch test
[root@dev lustre]# ln test link
[root@dev lustre]# unlink test
[root@dev lustre]# unlink link

Changelog:

16 01CREAT 22:40:29.374818949 2025.03.27 0x0 t=[0x200000402:0xa:0x0] j=touch.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] test
17 11CLOSE 22:40:29.378415970 2025.03.27 0x42 t=[0x200000402:0xa:0x0] j=touch.0 ef=0xf u=0:0 nid=0@lo
18 03HLINK 22:40:38.076554006 2025.03.27 0x0 t=[0x200000402:0xa:0x0] j=ln.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] link
19 06UNLNK 22:40:58.921224020 2025.03.27 0x0 t=[0x200000402:0xa:0x0] j=unlink.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] test
20 06UNLNK 22:41:04.842415511 2025.03.27 0x1 t=[0x200000402:0xa:0x0] j=unlink.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] link

The flag CLF_UNLINK_LAST (0x1) is set for the last unlink

Reproducer

[root@dev lustre]# touch test
[root@dev lustre]# ln test link
[root@dev lustre]# tail -f test &
[3] 20213
[root@dev lustre]# unlink test
[root@dev lustre]# unlink link
[root@dev lustre]# fg
tail -f test
^C

Changelog:

21 01CREAT 22:46:47.067992987 2025.03.27 0x0 t=[0x200000402:0xb:0x0] j=touch.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] test
22 11CLOSE 22:46:47.073296359 2025.03.27 0x42 t=[0x200000402:0xb:0x0] j=touch.0 ef=0xf u=0:0 nid=0@lo
23 03HLINK 22:46:50.963344725 2025.03.27 0x0 t=[0x200000402:0xb:0x0] j=ln.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] link
24 06UNLNK 22:47:25.655733670 2025.03.27 0x0 t=[0x200000402:0xb:0x0] j=unlink.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] test
25 06UNLNK 22:47:30.061160556 2025.03.27 0x0 t=[0x200000402:0xb:0x0] j=unlink.0 ef=0xf u=0:0 nid=0@lo p=[0x200000007:0x1:0x0] link

The flag CLF_UNLINK_LAST (0x1) is not set for the last unlink.