[GFS2] delay glock demote for a minimum hold time
When a lot of IO, with some distributed mmap IO, is run on a GFS2 filesystem in
a cluster, it will deadlock. The reason is that do_no_page() will repeatedly
call gfs2_sharewrite_nopage(), because each node keeps giving up the glock
too early, and is forced to call unmap_mapping_range(). This bumps the
mapping->truncate_count sequence count, forcing do_no_page() to retry. This
patch institutes a minimum glock hold time a tenth a second. This insures
that even in heavy contention cases, the node has enough time to get some
useful work done before it gives up the glock.
A second issue is that when gfs2_glock_dq() is called from within a page fault
to demote a lock, and the associated page needs to be written out, it will
try to acqire a lock on it, but it has already been locked at a higher level.
This patch puts makes gfs2_glock_dq() use the work queue as well, to avoid this
issue. This is the same patch as Steve Whitehouse originally proposed to fix
this issue, execpt that gfs2_glock_dq() now grabs a reference to the glock
before it queues up the work on it.
Signed-off-by: Benjamin E. Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 1390b30..23b611a 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -11,6 +11,7 @@
#define __INCORE_DOT_H__
#include <linux/fs.h>
+#include <linux/workqueue.h>
#define DIO_WAIT 0x00000010
#define DIO_METADATA 0x00000020
@@ -130,6 +131,7 @@
int (*go_lock) (struct gfs2_holder *gh);
void (*go_unlock) (struct gfs2_holder *gh);
const int go_type;
+ const unsigned long go_min_hold_time;
};
enum {
@@ -161,6 +163,7 @@
GLF_LOCK = 1,
GLF_STICKY = 2,
GLF_DEMOTE = 3,
+ GLF_PENDING_DEMOTE = 4,
GLF_DIRTY = 5,
};
@@ -193,6 +196,7 @@
u64 gl_vn;
unsigned long gl_stamp;
+ unsigned long gl_tchange;
void *gl_object;
struct list_head gl_reclaim;
@@ -203,6 +207,7 @@
struct gfs2_log_element gl_le;
struct list_head gl_ail_list;
atomic_t gl_ail_count;
+ struct delayed_work gl_work;
};
struct gfs2_alloc {