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, 1 insertions, 41 deletions

diff --git a/fs/gfs2/sys.c b/fs/gfs2/sys.c
index 59e36fd80903..67ba5b7b759b 100644
--- a/fs/gfs2/sys.c
+++ b/fs/gfs2/sys.c
@@ -263,7 +263,6 @@ ARGS_ATTR(localcaching,    "%d\n");
 ARGS_ATTR(localflocks,     "%d\n");
 ARGS_ATTR(debug,           "%d\n");
 ARGS_ATTR(upgrade,         "%d\n");
-ARGS_ATTR(num_glockd,      "%u\n");
 ARGS_ATTR(posix_acl,       "%d\n");
 ARGS_ATTR(quota,           "%u\n");
 ARGS_ATTR(suiddir,         "%d\n");
@@ -279,7 +278,6 @@ static struct attribute *args_attrs[] = {
 	&args_attr_localflocks.attr,
 	&args_attr_debug.attr,
 	&args_attr_upgrade.attr,
-	&args_attr_num_glockd.attr,
 	&args_attr_posix_acl.attr,
 	&args_attr_quota.attr,
 	&args_attr_suiddir.attr,
@@ -288,30 +286,6 @@ static struct attribute *args_attrs[] = {
 };
 
 /*
- * display counters from superblock
- */
-
-struct counters_attr {
-	struct attribute attr;
-	ssize_t (*show)(struct gfs2_sbd *, char *);
-};
-
-#define COUNTERS_ATTR(name, fmt)                                            \
-static ssize_t name##_show(struct gfs2_sbd *sdp, char *buf)                 \
-{                                                                           \
-	return snprintf(buf, PAGE_SIZE, fmt,                                \
-			(unsigned int)atomic_read(&sdp->sd_##name));        \
-}                                                                           \
-static struct counters_attr counters_attr_##name = __ATTR_RO(name)
-
-COUNTERS_ATTR(reclaimed,        "%u\n");
-
-static struct attribute *counters_attrs[] = {
-	&counters_attr_reclaimed.attr,
-	NULL,
-};
-
-/*
  * get and set struct gfs2_tune fields
  */
 
@@ -393,7 +367,6 @@ static ssize_t name##_store(struct gfs2_sbd *sdp, const char *buf, size_t len)\
 }                                                                             \
 TUNE_ATTR_2(name, name##_store)
 
-TUNE_ATTR(demote_secs, 0);
 TUNE_ATTR(incore_log_blocks, 0);
 TUNE_ATTR(log_flush_secs, 0);
 TUNE_ATTR(quota_warn_period, 0);
@@ -411,7 +384,6 @@ TUNE_ATTR_DAEMON(logd_secs, logd_process);
 TUNE_ATTR_3(quota_scale, quota_scale_show, quota_scale_store);
 
 static struct attribute *tune_attrs[] = {
-	&tune_attr_demote_secs.attr,
 	&tune_attr_incore_log_blocks.attr,
 	&tune_attr_log_flush_secs.attr,
 	&tune_attr_quota_warn_period.attr,
@@ -435,11 +407,6 @@ static struct attribute_group lockstruct_group = {
 	.attrs = lockstruct_attrs,
 };
 
-static struct attribute_group counters_group = {
-	.name = "counters",
-	.attrs = counters_attrs,
-};
-
 static struct attribute_group args_group = {
 	.name = "args",
 	.attrs = args_attrs,
@@ -464,13 +431,9 @@ int gfs2_sys_fs_add(struct gfs2_sbd *sdp)
 	if (error)
 		goto fail_reg;
 
-	error = sysfs_create_group(&sdp->sd_kobj, &counters_group);
-	if (error)
-		goto fail_lockstruct;
-
 	error = sysfs_create_group(&sdp->sd_kobj, &args_group);
 	if (error)
-		goto fail_counters;
+		goto fail_lockstruct;
 
 	error = sysfs_create_group(&sdp->sd_kobj, &tune_group);
 	if (error)
@@ -481,8 +444,6 @@ int gfs2_sys_fs_add(struct gfs2_sbd *sdp)
 
 fail_args:
 	sysfs_remove_group(&sdp->sd_kobj, &args_group);
-fail_counters:
-	sysfs_remove_group(&sdp->sd_kobj, &counters_group);
 fail_lockstruct:
 	sysfs_remove_group(&sdp->sd_kobj, &lockstruct_group);
 fail_reg:
@@ -496,7 +457,6 @@ void gfs2_sys_fs_del(struct gfs2_sbd *sdp)
 {
 	sysfs_remove_group(&sdp->sd_kobj, &tune_group);
 	sysfs_remove_group(&sdp->sd_kobj, &args_group);
-	sysfs_remove_group(&sdp->sd_kobj, &counters_group);
 	sysfs_remove_group(&sdp->sd_kobj, &lockstruct_group);
 	kobject_put(&sdp->sd_kobj);
 }