[LU-18791] report overflowed nlink counter correctly for striped dirs.

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.17.0
• Labels: patch
• Severity: 3
• Assignee: Alexander Zarochentsev
• Reporter: Alexander Zarochentsev

Description

on ldiskfs backend, if shards of a striped dir have more than ~64k subdirectories , the reported nlink attribute for the striped directory is incorrect:

[root@rocky tests]# ../utils/lfs mkdir -c 2 /mnt/lustre/dir-c2
[root@rocky tests]# for x in {0..160}; do for y in {0..999} ; do mkdir /mnt/lustre/dir-c2/$x-$y; done; echo .. ${x}k ..; done
.. 0k ..
.. 1k ..
.. 2k ..
.. 3k ..
.. 4k ..
...
.. 160k ..
[root@rocky tests]# stat /mnt/lustre/dir-c2
  File: /mnt/lustre/dir-c2
  Size: 7815168   	Blocks: 15280      IO Block: 1048576 directory
Device: 2c54f966h/743766374d	Inode: 144115205289279489  Links: 0
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2025-03-10 19:50:11.000000000 +0300
Modify: 2025-03-10 19:53:07.000000000 +0300
Change: 2025-03-10 19:53:07.000000000 +0300
 Birth: 2025-03-10 19:50:11.000000000 +0300
[root@rocky tests]# 

as you see, the nlink count is 0.

Comments

[Peter Jones]

Merged for 2.17

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/c/fs/lustre-release/+/58357/
Subject: LU-18791 lmv: report an overflowed nlink correctly
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: b968372d746012a868c742d75ac8062cc361a07a

[Alexander Zarochentsev]

with the same test (w/o the fix) on 3-striped dir we get a negative number truncated to u32, which is also incorrect.

[root@rocky tests]# ../utils/lfs mkdir -c 3 /mnt/lustre/dir-c3
[root@rocky tests]# ../utils/lfs getdirstripe /mnt/lustre/dir-c3
lmv_stripe_count: 3 lmv_stripe_offset: 0 lmv_hash_type: crush
mdtidx		 FID[seq:oid:ver]
     0		 [0x200000400:0x2:0x0]		
     2		 [0x280000402:0x2:0x0]		
     1		 [0x240000402:0x2:0x0]		
[root@rocky tests]# for x in {0..200}; do for y in {0..999} ; do mkdir /mnt/lustre/dir-c3/$x-$y; done; echo .. ${x}k ..; done
.. 0k ..
.. 1k ..
.. 2k ..
.. 3k ..
.. 4k ..
.. 5k ..
...
.. 199k ..
.. 200k ..
[root@rocky tests]# stat /mnt/lustre/dir-c3
  File: /mnt/lustre/dir-c3
  Size: 10043392  	Blocks: 19640      IO Block: 1048576 directory
Device: 2c54f966h/743766374d	Inode: 144115205306056705  Links: 64378
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2025-03-10 20:31:27.000000000 +0300
Modify: 2025-03-10 20:34:53.000000000 +0300
Change: 2025-03-10 20:34:53.000000000 +0300
 Birth: 2025-03-10 20:31:27.000000000 +0300
[root@rocky tests]# 

[Alexander Zarochentsev]

repeating the test with the fix applied:

.. 144k ..
.. 145k ..
.. 146k ..
.. 147k ..
.. 148k ..
.. 149k ..
.. 150k ..
.. 151k ..
.. 152k ..
.. 153k ..
.. 154k ..
.. 155k ..
.. 156k ..
.. 157k ..
.. 158k ..
.. 159k ..
.. 160k ..
[root@rocky tests]# stat /mnt/lustre/dir-c2
  File: /mnt/lustre/dir-c2
  Size: 7856128   	Blocks: 15360      IO Block: 1048576 directory
Device: 2c54f966h/743766374d	Inode: 144115205289279489  Links: 1
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2025-03-10 20:09:38.000000000 +0300
Modify: 2025-03-10 20:12:09.000000000 +0300
Change: 2025-03-10 20:12:09.000000000 +0300
 Birth: 2025-03-10 20:09:38.000000000 +0300
[root@rocky tests]# 

nlinks = 1, as in ldiskfs.

[Gerrit Updater]

"Alexander Zarochentsev <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/58357
Subject: LU-18791 lmv: report an overflowed nlink correctly
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 6389649d8fa31af66e2c84d6146a5b3c815fbf52