[LU-9986] Cannot write to ldiskfs prealloc_table proc file

• Type: Bug
• Resolution: Duplicate
• Priority: Minor
• Fix Version/s: Lustre 2.11.0
• Affects Version/s: Lustre 2.10.0
• Environment: RHEL7, SLES12
• Severity: 3
• Assignee: Yang Sheng
• Reporter: Ian Ziemba (Inactive)

Description

For Lustre servers using ldiskfs, the prealloc_table cannot be updated through the proc file.

# echo 1024 2048 4096 > /proc/fs/ldiskfs/md0/prealloc_table
-bash: echo: write error: Invalid argument

# ls -l /proc/fs/ldiskfs/md0/prealloc_table
-rw-r--r-- 1 root root 0 Sep 13 04:42 /proc/fs/ldiskfs/md0/prealloc_table

The issue appears to be caused by the usage of kstrtol in ldiskfs_mb_prealloc_table_proc_write. Unlike simple_strtol, kstrtol does not provide an end pointer. This causes -EINVAL to be returned due to the cur pointer not getting updated.