GFS2: Kill two daemons with one patch

This patch removes the two daemons, gfs2_scand and gfs2_glockd
and replaces them with a shrinker which is called from the VM.

The net result is that GFS2 responds better when there is memory
pressure, since it shrinks the glock cache at the same rate
as the VFS shrinks the dcache and icache. There are no longer
any time based criteria for shrinking glocks, they are kept
until such time as the VM asks for more memory and then we
demote just as many glocks as required.

There are potential future changes to this code, including the
possibility of sorting the glocks which are to be written back
into inode number order, to get a better I/O ordering. It would
be very useful to have an elevator based workqueue implementation
for this, as that would automatically deal with the read I/O cases
at the same time.

This patch is my answer to Andrew Morton's remark, made during
the initial review of GFS2, asking why GFS2 needs so many kernel
threads, the answer being that it doesn't :-) This patch is a
net loss of about 200 lines of code.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 2 insertions, 14 deletions

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index dd7d0f8f357..608849d0002 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -125,7 +125,7 @@ struct gfs2_glock_operations {
 	void (*go_xmote_th) (struct gfs2_glock *gl);
 	int (*go_xmote_bh) (struct gfs2_glock *gl, struct gfs2_holder *gh);
 	void (*go_inval) (struct gfs2_glock *gl, int flags);
-	int (*go_demote_ok) (struct gfs2_glock *gl);
+	int (*go_demote_ok) (const struct gfs2_glock *gl);
 	int (*go_lock) (struct gfs2_holder *gh);
 	void (*go_unlock) (struct gfs2_holder *gh);
 	int (*go_dump)(struct seq_file *seq, const struct gfs2_glock *gl);
@@ -155,7 +155,6 @@ struct gfs2_holder {
 
 enum {
 	GLF_LOCK			= 1,
-	GLF_STICKY			= 2,
 	GLF_DEMOTE			= 3,
 	GLF_PENDING_DEMOTE		= 4,
 	GLF_DEMOTE_IN_PROGRESS		= 5,
@@ -190,7 +189,7 @@ struct gfs2_glock {
 	unsigned long gl_tchange;
 	void *gl_object;
 
-	struct list_head gl_reclaim;
+	struct list_head gl_lru;
 
 	struct gfs2_sbd *gl_sbd;
 
@@ -397,7 +396,6 @@ struct gfs2_args {
 struct gfs2_tune {
 	spinlock_t gt_spin;
 
-	unsigned int gt_demote_secs; /* Cache retention for unheld glock */
 	unsigned int gt_incore_log_blocks;
 	unsigned int gt_log_flush_secs;
 
@@ -478,10 +476,6 @@ struct gfs2_sbd {
 	/* Lock Stuff */
 
 	struct lm_lockstruct sd_lockstruct;
-	struct list_head sd_reclaim_list;
-	spinlock_t sd_reclaim_lock;
-	wait_queue_head_t sd_reclaim_wq;
-	atomic_t sd_reclaim_count;
 	struct gfs2_holder sd_live_gh;
 	struct gfs2_glock *sd_rename_gl;
 	struct gfs2_glock *sd_trans_gl;
@@ -541,8 +535,6 @@ struct gfs2_sbd {
 	struct task_struct *sd_recoverd_process;
 	struct task_struct *sd_logd_process;
 	struct task_struct *sd_quotad_process;
-	struct task_struct *sd_glockd_process[GFS2_GLOCKD_MAX];
-	unsigned int sd_glockd_num;
 
 	/* Quota stuff */
 
@@ -615,10 +607,6 @@ struct gfs2_sbd {
 	struct mutex sd_freeze_lock;
 	unsigned int sd_freeze_count;
 
-	/* Counters */
-
-	atomic_t sd_reclaimed;
-
 	char sd_fsname[GFS2_FSNAME_LEN];
 	char sd_table_name[GFS2_FSNAME_LEN];
 	char sd_proto_name[GFS2_FSNAME_LEN];