Commit 06e908cd authored by Bob Peterson's avatar Bob Peterson Committed by Andreas Gruenbacher
Browse files

gfs2: Allow node-wide exclusive glock sharing 



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: default avatarBob Peterson <rpeterso@redhat.com>
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent 9e514605

fs/gfs2/glock.c

+19 −3
Original line number Diff line number Diff line
@@ -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_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) && gh != gh_head)

		     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)

fs/gfs2/glock.h

+6 −0
Original line number Diff line number Diff line
@@ -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