[LU-19858] Remote agent entry incorrectly unlinked (REMOTE_PARENT_DIR/<file_fid>)

• Type: Bug
• Resolution: Unresolved
• Priority: Major
• Severity: 3
• Assignee: Etienne Aujames
• Reporter: Etienne Aujames

Description

This happens when linkea overflow: some remote entries are not accounted in linkea (trusted.link).

Reproducer (lustre master branch):
Create 1000 hardlinks to overflow linkea (4K max):

[root@client-el8 mdt1]# cd ../mdt0
[root@client-el8 mdt0]# touch test
[root@client-el8 mdt0]# printf "%s\n" test_link{1..1000} | xargs -n1 ln test   
[root@client-el8 mdt0]# debugfs -c -R 'stat /ROOT/mdt0/test' /dev/mapper/mds1_flakey                                                                                                                                                          
debugfs 1.47.3-wc2 (11-Nov-2025)
Inode: 166   Type: regular    Mode:  0644   Flags: 0x80000
Generation: 2615803926    Version: 0x00000001:0000139e
User:     0   Group:     0   Project:     0   Size: 0
File ACL: 0
Links: 1001   Blockcount: 8
Fragment:  Address: 0    Number: 0    Size: 0
 ctime: 0x6985bae8:00000000 -- Fri Feb  6 10:56:56 2026
 atime: 0x6985ba99:00000000 -- Fri Feb  6 10:55:37 2026
 mtime: 0x6985ba99:00000000 -- Fri Feb  6 10:55:37 2026
crtime: 0x6985ba99:27a3b61c -- Fri Feb  6 10:55:37 2026
Size of extra inode fields: 32
Extended attributes:
  lma: fid=[0x200000402:0x3:0x0] compat=0 incompat=0
  trusted.lov (56) = d0 0b d1 0b 01 00 00 00 03 00 00 00 00 00 00 00 02 04 00 00 02 00 00 00 00 00 10 00 01 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 
  trusted.som (24) = 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
  inode <167> linkea: idx=0 parent=[0x200000402:0x1:0x0] name='test'
          idx=1 parent=[0x200000402:0x1:0x0] name='test_link1'
....
          idx=138 parent=[0x200000402:0x1:0x0] name='test_link138'
EXTENTS:

move all entries to create 1000 remote entries

[root@client-el8 mdt0]# printf "%s\n" test test_link{1..1000} | xargs -I{} mv {} ../mdt1
[root@client-el8 mdt0]# debugfs -c -R 'ls /REMOTE_PARENT_DIR' /dev/mapper/mds1_flakey 
debugfs 1.47.3-wc2 (11-Nov-2025)
 25001  (12) .    2  (12) ..    166  (4072) 0x200000402:0x3:0x0

Unlink all the entries register in linkea:

[root@client-el8 mdt0]# cd ../mdt1
[root@client-el8 mdt1]# printf "%s\n" test test_link{1..138} | xargs -n1 unlink

Now the remote agent entry is removed:

[root@client-el8 mdt1]# debugfs -c -R 'ls /REMOTE_PARENT_DIR' /dev/mapper/mds1_flakey 
debugfs 1.47.3-wc2 (11-Nov-2025)
 25001  (12) .    2  (4084) ..   

No more entries reference this inode, so e2fsck complains about it:

[root@client-el8 mdt1]# cd
[root@client-el8 ~]# umount /dev/mapper/mds1_flakey 
[root@client-el8 ~]# e2fsck -nvf /dev/mapper/mds1_flakey
e2fsck 1.47.3-wc2 (11-Nov-2025)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Unattached inode 166
Connect to /lost+found? no

Pass 5: Checking group summary information

lustre-MDT0000: ********** WARNING: Filesystem still has errors **********


         280 inodes used (0.28%, out of 100000)
           5 non-contiguous files (1.8%)
           1 non-contiguous directory (0.4%)
             # of inodes with ind/dind/tind blocks: 0/0/0
             Extent depth histogram: 273/1
       30083 blocks used (48.13%, out of 62500)
           0 bad blocks
           1 large file

         151 regular files
         119 directories
           0 character device files
           0 block device files
           0 fifos
           0 links
           0 symbolic links (0 fast symbolic links)
           0 sockets
------------
         269 files

Issue Links

• is related to: LU-11446 ldiskfs inodes nlink mismatch with DNE