From: Bob Peterson <rpete...@redhat.com>
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 as
well. (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 <rpete...@redhat.com>
---
fs/gfs2/glock.c | 26 ++++++++++++++++++++++----
fs/gfs2/glock.h | 6 ++++++
2 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 05431324b262b..1c07a1819c1b0 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -279,10 +279,26 @@ 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_entry(gl->gl_holders.next,
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;
+ const struct gfs2_holder *gh_head = list_entry(gl->gl_holders.next,
+ 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))
+ return 0;
+ }
if (gl->gl_state == gh->gh_state)
return 1;
if (gh->gh_flags & GL_EXACT)
@@ -1682,6 +1698,8 @@ 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)
diff --git a/fs/gfs2/glock.h b/fs/gfs2/glock.h
index 5e12220cc0c24..3a3c1bd5b2d89 100644
--- a/fs/gfs2/glock.h
+++ b/fs/gfs2/glock.h
@@ -78,6 +78,11 @@ 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
@@ -85,6 +90,7 @@ 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
--
2.19.1.546.g028f9c799.dirty
