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gfs2: Allow node-wide exclusive glock sharing

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Introduce a new LM_FLAG_NODE_SCOPE glock holder flag: when taking a
glock in LM_ST_EXCLUSIVE (EX) mode and with the LM_FLAG_NODE_SCOPE flag
set, the exclusive lock is shared among all local processes who are
holding the glock in EX mode and have the LM_FLAG_NODE_SCOPE flag set.
From the point of view of other nodes, the lock is still held
exclusively.

A future patch will start using this flag to improve performance with
rgrp sharing.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Bob Peterson 2018-04-18 13:58:19 -07:00 committed by Andreas Gruenbacher
parent 9e514605c7
commit 06e908cd9e
2 changed files with 25 additions and 3 deletions
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22
fs/gfs2/glock.c
View file

@ -313,9 +313,23 @@ void gfs2_glock_put(struct gfs2_glock *gl)
static inline int may_grant(const struct gfs2_glock *gl, const struct gfs2_holder *gh)
{
const struct gfs2_holder *gh_head = list_first_entry(&gl->gl_holders, const struct gfs2_holder, gh_list);
if ((gh->gh_state == LM_ST_EXCLUSIVE ||
gh_head->gh_state == LM_ST_EXCLUSIVE) && gh != gh_head)
return 0;
if (gh != gh_head) {
/**
* Here we make a special exception to grant holders who agree
* to share the EX lock with other holders who also have the
* bit set. If the original holder has the LM_FLAG_NODE_SCOPE bit
* is set, we grant more holders with the bit set.
*/
if (gh_head->gh_state == LM_ST_EXCLUSIVE &&
(gh_head->gh_flags & LM_FLAG_NODE_SCOPE) &&
gh->gh_state == LM_ST_EXCLUSIVE &&
(gh->gh_flags & LM_FLAG_NODE_SCOPE))
return 1;
if ((gh->gh_state == LM_ST_EXCLUSIVE ||
gh_head->gh_state == LM_ST_EXCLUSIVE))
return 0;
}
if (gl->gl_state == gh->gh_state)
return 1;
if (gh->gh_flags & GL_EXACT)
@ -2030,6 +2044,8 @@ static const char *hflags2str(char *buf, u16 flags, unsigned long iflags)
*p++ = 'A';
if (flags & LM_FLAG_PRIORITY)
*p++ = 'p';
if (flags & LM_FLAG_NODE_SCOPE)
*p++ = 'n';
if (flags & GL_ASYNC)
*p++ = 'a';
if (flags & GL_EXACT)

6
fs/gfs2/glock.h
View file

@ -75,6 +75,11 @@ enum {
* request and directly join the other shared lock. A shared lock request
* without the priority flag might be forced to wait until the deferred
* requested had acquired and released the lock.
*
* LM_FLAG_NODE_SCOPE
* This holder agrees to share the lock within this node. In other words,
* the glock is held in EX mode according to DLM, but local holders on the
* same node can share it.
*/
#define LM_FLAG_TRY 0x0001
@ -82,6 +87,7 @@ enum {
#define LM_FLAG_NOEXP 0x0004
#define LM_FLAG_ANY 0x0008
#define LM_FLAG_PRIORITY 0x0010
#define LM_FLAG_NODE_SCOPE 0x0020
#define GL_ASYNC 0x0040
#define GL_EXACT 0x0080
#define GL_SKIP 0x0100