[LU-18620] LFSCK does not fix broken agent entries

• Type: Bug
• Resolution: Unresolved
• Priority: Major
• Severity: 3
• Assignee: Alexander Zarochentsev
• Reporter: Alexander Zarochentsev

Description

Here my attempt to re-create a missing agent entry for a remote stripe of a striped dir :

[root@rocky tests]# ../utils/lfs mkdir -H fnv_1a_64 -c 2 /mnt/lustre/dir-c2
[root@rocky tests]# ../utils/lfs path2fid /mnt/lustre/dir-c2
[0x200000402:0x1:0x0]
[root@rocky tests]# ../utils/lfs getdirstripe /mnt/lustre/dir-c2
lmv_stripe_count: 2 lmv_stripe_offset: 0 lmv_hash_type: fnv_1a_64
mdtidx		 FID[seq:oid:ver]
     0		 [0x200000400:0x2:0x0]		
     1		 [0x240000401:0x2:0x0]		
[root@rocky tests]# debugfs /dev/mapper/mds2_flakey  -R "ls -lD REMOTE_PARENT_DIR"
debugfs 1.46.2.wc5 (26-Mar-2022)
  25001   40755 (2)      0      0    4096  9-Jan-2025 16:04 .
      2   40755 (2)      0      0    4096  9-Jan-2025 15:31 ..
  25047   40755 (2)      0      0    4096  9-Jan-2025 16:04 0x240000401:0x2:0x0

[root@rocky tests]# debugfs /dev/mapper/mds1_flakey  -R "ls ROOT/dir-c2"
debugfs 1.46.2.wc5 (26-Mar-2022)
 25049  (12) .    25043  (28) ..    25050  (52) [0x200000400:0x2:0x0]:0   
 25051  (4004) [0x240000401:0x2:0x0]:1   
[root@rocky tests]# debugfs /dev/mapper/mds1_flakey  -R "ls -lD ROOT/dir-c2"
debugfs 1.46.2.wc5 (26-Mar-2022)
  25049   40755 (2)      0      0    4096  9-Jan-2025 16:04 .
  25043   40755 (18)      0      0    4096  9-Jan-2025 16:04 fid:[0x200000007:0x1:0x0] ..
  25050   40755 (18)      0      0    4096  9-Jan-2025 16:04 fid:[0x200000400:0x2:0x0] [0x200000400:0x2:0x0]:0
  25051   40000 (18)      0      0    4096  1-Jan-1970 03:00 fid:[0x240000401:0x2:0x0] [0x240000401:0x2:0x0]:1

removing the agent entry:

[root@rocky tests]# umount /mnt/lustre-mds2
[root@rocky tests]# debugfs -w /dev/mapper/mds2_flakey  -R "unlink REMOTE_PARENT_DIR/0x240000401:0x2:0x0"
debugfs 1.46.2.wc5 (26-Mar-2022)
[root@rocky tests]# debugfs /dev/mapper/mds2_flakey  -R "ls -lD REMOTE_PARENT_DIR"
debugfs 1.46.2.wc5 (26-Mar-2022)
  25001   40755 (2)      0      0    4096  9-Jan-2025 16:04 .
      2   40755 (2)      0      0    4096  9-Jan-2025 15:31 ..

starting LFSCK namespace

[root@rocky tests]# mount -t lustre /dev/mapper/mds2_flakey /mnt/lustre-mds2
[root@rocky tests]# ../utils/lctl lfsck_start -M lustre-MDT0000  -t namespace
Started LFSCK on the device lustre-MDT0000: scrub namespace
[root@rocky tests]# ../utils/lctl lfsck_start -M lustre-MDT0001  -t namespace
Started LFSCK on the device lustre-MDT0001: scrub namespace

checking the results of the LFSCK runs, seeing that
an object with some new FID created and new agent entry inserted into /REMOTE_PARENT_DIR :

[root@rocky tests]# debugfs /dev/mapper/mds2_flakey  -R "ls -lD REMOTE_PARENT_DIR"
debugfs 1.46.2.wc5 (26-Mar-2022)
  25001   40755 (2)      0      0    4096  9-Jan-2025 16:07 .
      2   40755 (2)      0      0    4096  9-Jan-2025 15:31 ..
  25048   40700 (2)      0      0    4096  9-Jan-2025 16:07 0x240000bd0:0x1:0x0

it is a different FID from the FID of the remote stripe:

[root@rocky tests]# debugfs /dev/mapper/mds1_flakey  -R "ls -lD ROOT/dir-c2"
debugfs 1.46.2.wc5 (26-Mar-2022)
  25049   40755 (2)      0      0    4096  9-Jan-2025 16:04 .
  25043   40755 (18)      0      0    4096  9-Jan-2025 16:04 fid:[0x200000007:0x1:0x0] ..
  25050   40755 (18)      0      0    4096  9-Jan-2025 16:04 fid:[0x200000400:0x2:0x0] [0x200000400:0x2:0x0]:0
  25051   40000 (18)      0      0    4096  1-Jan-1970 03:00 fid:[0x240000401:0x2:0x0] [0x240000401:0x2:0x0]:1

the dir inode with the remote stripe still in use and still an orphan, not connected to any dir:

[root@rocky tests]# debugfs /dev/mapper/mds2_flakey  
debugfs 1.46.2.wc5 (26-Mar-2022)
debugfs:  testi <25047>
Inode 25047 is marked in use
debugfs:  ncheck 25047
Inode	Pathname
debugfs: