I'm sponsoring the following fast-track for Bob Mastors.
This case is an update to PSARC 2007/456 Vnode Specific Data and adds
a new field to the vnode structure (in sys/vnode.h): v_vsd_lock.
The case seeks Minor binding which matches the binding of the original
case. The timer expires on June 12, 2009.
Template Version: @(#)sac_nextcase 1.68 02/23/09 SMI
This information is Copyright 2009 Sun Microsystems
1. Introduction
1.1. Project/Component Working Name:
VSD locking update
1.2. Name of Document Author/Supplier:
Author: Bob Mastors
1.3 Date of This Document:
05 June, 2009
4. Technical Description
PSARC 2007/456 Vnode Specific Data was created to easily associate
project specific data with a vnode. The current implementation
requires consumers of vsd_get() and vsd_set() to hold the vnode v_lock
mutex across the calls. However, vsd_set() may go to sleep on
kmem_alloc(). This could cause the system to deadlock if the vnode had
dirty pages that needed to be written. This problem is described by:
6839233 VSD usage of v_lock could cause deadlock
The solution adds a new mutex to vnode_t:
kmutex_t v_vsd_lock; /* protects v_vsd field */
Consumers of vsd_get() and vsd_set() would hold v_vsd_lock across the
calls instead of v_lock. There are no lock ordering issues since the
locks are independent and there is no reason to hold both simultaneously.
Currently, the only ON consumer of vsd_get() and vsd_set() is NFS.
Exported Interfaces
Interface Name | Classification | Comments
=================================================================
| |
v_vsd_lock | Consolidation | New mutex in the vnode structure
| Private | to protect v_vsd field
6. Resources and Schedule
6.4. Steering Committee requested information
6.4.1. Consolidation C-team Name:
ON
6.5. ARC review type: FastTrack
6.6. ARC Exposure: open
