[LU-3671] why are permission changes synchronous?

• Type: Bug
• Resolution: Fixed
• Priority: Critical
• Fix Version/s: Lustre 2.5.0
• Affects Version/s: Lustre 2.4.0
• Labels: zfs
• Severity: 3
• Assignee: Lai Siyao
• Reporter: Ned Bass (Inactive)

Description

mdd_acl_set() sets the ACL xattr synchronously if /proc/fs/lustre/mdd/lustre-MDT0000/sync_permission is set (it is set by default). This can have a large performance impact for operations like cp -a or tar --xattr. Should this be the default behavior? How does this relate to other permissions-related changed like chown, chmod, etc.? It would be good to explain the security implications of this setting in code comments and in the Lustre manual.

Some background information:

http://wiki.lustre.org/index.php/Architecture_-_Version_Based_Recovery#Permissions
https://projectlava.xyratex.com/show_bug.cgi?id=15390
http://git.whamcloud.com/gitweb?p=lustre.git;a=commit;h=0509770778396825ba1d7f1b42be5993aac1d6f3

LLNL-bug-ID: TOSS-2207

Issue Links

• duplicates: LUDOC-180 documentation for the MDS sync_permission /proc tunable
• is related to: LU-3660 Can't disable ACL support with ZFS MDT
• is related to: LU-7239 mdd_attr_set() synchronous when it need not be