[LU-10276] Revise what MDS_INODELOCK_XATTR protects

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Assignee: WC Triage
• Reporter: Li Wei (Inactive)

Description

MDS_INODELOCK_XATTR has been protecting all EAs of an inode since its introduction for client-side EA caching. Because some EAs are used internally, the set of procedures contending for MDS_INODELOCK_XATTR has went beyond SETXATTR, GETXATTR. A few examples:

• LINK, UNLINK, and RENAME take MDS_INODELOCK_XATTR for XATTR_NAME_LINK.
• HSM_STATE_SET, mdt_hsm_release(), mdt_add_dirty_flag() take MDS_INODELOCK_XATTR for XATTR_NAME_HSM.

Some of these may have an unnecessary negative effect on client-side EA caching efficiency.

We might want to consider removing internal EAs from the scope of MDS_INODELOCK_XATTR. Potential questions include:

• Clients wouldn't be able to do listxattr() completely from EA caches. Would this affect any applications we care about?
• How to handle older clients who assume MDS_INODELOCK_XATTR protects all EAs?

Issue Links

• is related to: LU-17238 negative xattr cache on client
• is related to: LU-2869 extended attribute cache for Lustre