[LU-6990] write error: Invalid argument when trying to set nosquash_nids

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.8.0
• Affects Version/s: Lustre 2.5.4
• Environment: Lustre 2.5.3.90
• Severity: 3
• Assignee: Emoly Liu
• Reporter: Bruno Travouillon (Inactive)

Description

Since our update from 2.5.3 to 2.5.3.90, we can't set the nosquash_nids parameter by writing into the procfile /proc/fs/lustre/mdt/scratch-MDT0000/nosquash_nids.

This is the method used by the shine tool for setting all the parameters.

[root@mds2 ~]# echo "192.168.101.13@tcp" > /proc/fs/lustre/mdt/scratch-MDT0000/nosquash_nids
-bash: echo: write error: Invalid argument

However, it works with 'lctl set_param' or 'echo -n'.

[root@mds2 ~]# echo -n "192.168.101.13@tcp" > /proc/fs/lustre/mdt/scratch-MDT0000/nosquash_nids
[root@mds2 ~]# cat /proc/fs/lustre/mdt/scratch-MDT0000/nosquash_nids
192.168.101.13@tcp
[root@mds2 ~]# lctl set_param mdt.scratch-MDT0000.nosquash_nids=192.168.0.13@tcp
mdt.scratch-MDT0000.nosquash_nids=192.168.0.13@tcp
[root@mds2 ~]# cat /proc/fs/lustre/mdt/scratch-MDT0000/nosquash_nids
192.168.0.13@tcp

It is related to LU-1778. The bug is in lprocfs_wr_nosquash_nids(). See lustre/obdclass/lprocfs_status.c (b2_5 branch, commit d82b4f54):

2789     if (count > 0 && kernbuf[count - 1] == '\n')
2790         kernbuf[count - 1] = '\0';

I don't understand why we need to replace \n by \0 since the nid parser seems to handle the newline.

Please let me know if you need further details.

Issue Links

• is related to: LU-1778 Root Squash is not always properly enforced