Merge: gfs2: Revise glock reference counting model

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5784

JIRA: https://issues.redhat.com/browse/RHEL-67675
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Approved-by: Abhi Das <adas@redhat.com>
Approved-by: Andrew Price <anprice@redhat.com>
Approved-by: Paul Evans <pevans@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Rado Vrbovsky <rvrbovsk@redhat.com>

Author: emmil

Documentation/filesystems/gfs2-glocks.rst

@@ -41,38 +41,37 @@ shared lock mode, SH. In GFS2 the DF mode is used exclusively for direct I/O
 operations. The glocks are basically a lock plus some routines which deal
 with cache management. The following rules apply for the cache:
 
-==========      ==========   ==============   ==========   ==============
-Glock mode      Cache data   Cache Metadata   Dirty Data   Dirty Metadata
-==========      ==========   ==============   ==========   ==============
-    UN             No              No             No            No
-    SH             Yes             Yes            No            No
-    DF             No              Yes            No            No
-    EX             Yes             Yes            Yes           Yes
-==========      ==========   ==============   ==========   ==============
+==========      ==============   ==========   ==========   ==============
+Glock mode      Cache Metadata   Cache data   Dirty Data   Dirty Metadata
+==========      ==============   ==========   ==========   ==============
+    UN                No            No            No            No
+    DF                Yes           No            No            No
+    SH                Yes           Yes           No            No
+    EX                Yes           Yes           Yes           Yes
+==========      ==============   ==========   ==========   ==============
 
 These rules are implemented using the various glock operations which
 are defined for each type of glock. Not all types of glocks use
 all the modes. Only inode glocks use the DF mode for example.
 
 Table of glock operations and per type constants:
 
-=============      =============================================================
+==============     =============================================================
 Field              Purpose
-=============      =============================================================
-go_xmote_th        Called before remote state change (e.g. to sync dirty data)
+==============     =============================================================
+go_sync            Called before remote state change (e.g. to sync dirty data)
 go_xmote_bh        Called after remote state change (e.g. to refill cache)
 go_inval           Called if remote state change requires invalidating the cache
-go_demote_ok       Returns boolean value of whether its ok to demote a glock
-                   (e.g. checks timeout, and that there is no cached data)
-go_lock            Called for the first local holder of a lock
-go_unlock          Called on the final local unlock of a lock
+go_instantiate     Called when a glock has been acquired
+go_held            Called every time a glock holder is acquired
 go_dump            Called to print content of object for debugfs file, or on
                    error to dump glock to the log.
-go_type            The type of the glock, ``LM_TYPE_*``
 go_callback	   Called if the DLM sends a callback to drop this lock
+go_unlocked        Called when a glock is unlocked (dlm_unlock())
+go_type            The type of the glock, ``LM_TYPE_*``
 go_flags	   GLOF_ASPACE is set, if the glock has an address space
                    associated with it
-=============      =============================================================
+==============     =============================================================
 
 The minimum hold time for each lock is the time after a remote lock
 grant for which we ignore remote demote requests. This is in order to
@@ -83,26 +82,24 @@ to by multiple nodes. By delaying the demotion in response to a
 remote callback, that gives the userspace program time to make
 some progress before the pages are unmapped.
 
-There is a plan to try and remove the go_lock and go_unlock callbacks
-if possible, in order to try and speed up the fast path though the locking.
-Also, eventually we hope to make the glock "EX" mode locally shared
-such that any local locking will be done with the i_mutex as required
-rather than via the glock.
+Eventually, we hope to make the glock "EX" mode locally shared such that any
+local locking will be done with the i_mutex as required rather than via the
+glock.
 
 Locking rules for glock operations:
 
-=============    ======================    =============================
+==============   ======================    =============================
 Operation        GLF_LOCK bit lock held    gl_lockref.lock spinlock held
-=============    ======================    =============================
-go_xmote_th           Yes                       No
+==============   ======================    =============================
+go_sync               Yes                       No
 go_xmote_bh           Yes                       No
 go_inval              Yes                       No
-go_demote_ok          Sometimes                 Yes
-go_lock               Yes                       No
-go_unlock             Yes                       No
+go_instantiate        No                        No
+go_held               No                        No
 go_dump               Sometimes                 Yes
 go_callback           Sometimes (N/A)           Yes
-=============    ======================    =============================
+go_unlocked           Yes                       No
+==============   ======================    =============================
 
 .. Note::