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authorSteven Whitehouse <swhiteho@redhat.com>2006-09-11 21:40:30 -0400
committerSteven Whitehouse <swhiteho@redhat.com>2006-09-11 21:40:30 -0400
commit24264434603cc102d71fb2a1b3b7e282a781f449 (patch)
tree18af5274fa222f0420df30651f57bab1eaf75eab /fs
parent94610610f10749c0e17b4d2840ff8a7cb636c413 (diff)
[GFS2] Rewrite of examine_bucket()
The existing implementation of this function in glock.c was not very efficient as it relied upon keeping a cursor element upon the hash chain in question and moving it along. This new version improves upon this by using the current element as a cursor. This is possible since we only look at the "next" element in the list after we've taken the read_lock() subsequent to calling the examiner function. Obviously we have to eventually drop the ref count that we are then left with and we cannot do that while holding the read_lock, so we do that next time we drop the lock. That means either just before we examine another glock, or when the loop has terminated. The new implementation has several advantages: it uses only a read_lock() rather than a write_lock(), so it can run simnultaneously with other code, it doesn't need a "plug" element, so that it removes a test not only from this list iterator, but from all the other glock list iterators too. So it makes things faster and smaller. Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/gfs2/glock.c95
-rw-r--r--fs/gfs2/incore.h1
2 files changed, 31 insertions, 65 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index b348053c436..b5effb9e4a3 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -18,6 +18,7 @@
#include <linux/kref.h>
#include <linux/kallsyms.h>
#include <linux/gfs2_ondisk.h>
+#include <linux/list.h>
#include <asm/uaccess.h>
#include "gfs2.h"
@@ -33,12 +34,6 @@
#include "super.h"
#include "util.h"
-/* Must be kept in sync with the beginning of struct gfs2_glock */
-struct glock_plug {
- struct list_head gl_list;
- unsigned long gl_flags;
-};
-
struct greedy {
struct gfs2_holder gr_gh;
struct work_struct gr_work;
@@ -52,6 +47,7 @@ typedef void (*glock_examiner) (struct gfs2_glock * gl);
static int gfs2_dump_lockstate(struct gfs2_sbd *sdp);
static int dump_glock(struct gfs2_glock *gl);
+static int dump_inode(struct gfs2_inode *ip);
#define GFS2_GL_HASH_SHIFT 13
#define GFS2_GL_HASH_SIZE (1 << GFS2_GL_HASH_SHIFT)
@@ -214,7 +210,7 @@ int gfs2_glock_put(struct gfs2_glock *gl)
write_lock(gl_lock_addr(gl->gl_hash));
if (kref_put(&gl->gl_ref, kill_glock)) {
- list_del_init(&gl_hash_table[gl->gl_hash].hb_list);
+ list_del_init(&gl->gl_list);
write_unlock(gl_lock_addr(gl->gl_hash));
BUG_ON(spin_is_locked(&gl->gl_spin));
glock_free(gl);
@@ -265,8 +261,6 @@ static struct gfs2_glock *search_bucket(unsigned int hash,
struct gfs2_glock *gl;
list_for_each_entry(gl, &gl_hash_table[hash].hb_list, gl_list) {
- if (test_bit(GLF_PLUG, &gl->gl_flags))
- continue;
if (!lm_name_equal(&gl->gl_name, name))
continue;
if (gl->gl_sbd != sdp)
@@ -1899,51 +1893,33 @@ void gfs2_reclaim_glock(struct gfs2_sbd *sdp)
static int examine_bucket(glock_examiner examiner, struct gfs2_sbd *sdp,
unsigned int hash)
{
- struct glock_plug plug;
- struct list_head *tmp;
- struct gfs2_glock *gl;
- int entries;
-
- /* Add "plug" to end of bucket list, work back up list from there */
- memset(&plug.gl_flags, 0, sizeof(unsigned long));
- set_bit(GLF_PLUG, &plug.gl_flags);
-
- write_lock(gl_lock_addr(hash));
- list_add(&plug.gl_list, &gl_hash_table[hash].hb_list);
- write_unlock(gl_lock_addr(hash));
-
- for (;;) {
- write_lock(gl_lock_addr(hash));
-
- for (;;) {
- tmp = plug.gl_list.next;
+ struct gfs2_glock *gl, *prev = NULL;
+ int has_entries = 0;
+ struct list_head *head = &gl_hash_table[hash].hb_list;
- if (tmp == &gl_hash_table[hash].hb_list) {
- list_del(&plug.gl_list);
- entries = !list_empty(&gl_hash_table[hash].hb_list);
- write_unlock(gl_lock_addr(hash));
- return entries;
- }
- gl = list_entry(tmp, struct gfs2_glock, gl_list);
-
- /* Move plug up list */
- list_move(&plug.gl_list, &gl->gl_list);
-
- if (test_bit(GLF_PLUG, &gl->gl_flags))
- continue;
- if (gl->gl_sbd != sdp)
- continue;
-
- /* examiner() must glock_put() */
+ read_lock(gl_lock_addr(hash));
+ /* Can't use list_for_each_entry - don't want prefetch here */
+ if (list_empty(head))
+ goto out;
+ has_entries = 1;
+ gl = list_entry(head->next, struct gfs2_glock, gl_list);
+ while(&gl->gl_list != head) {
+ if (gl->gl_sbd == sdp) {
gfs2_glock_hold(gl);
-
- break;
+ read_unlock(gl_lock_addr(hash));
+ if (prev)
+ gfs2_glock_put(prev);
+ prev = gl;
+ examiner(gl);
+ read_lock(gl_lock_addr(hash));
}
-
- write_unlock(gl_lock_addr(hash));
-
- examiner(gl);
+ gl = list_entry(gl->gl_list.next, struct gfs2_glock, gl_list);
}
+out:
+ read_unlock(gl_lock_addr(hash));
+ if (prev)
+ gfs2_glock_put(prev);
+ return has_entries;
}
/**
@@ -1955,23 +1931,19 @@ static int examine_bucket(glock_examiner examiner, struct gfs2_sbd *sdp,
static void scan_glock(struct gfs2_glock *gl)
{
if (gl->gl_ops == &gfs2_inode_glops)
- goto out;
+ return;
if (gfs2_glmutex_trylock(gl)) {
if (queue_empty(gl, &gl->gl_holders) &&
- gl->gl_state != LM_ST_UNLOCKED &&
- demote_ok(gl))
+ gl->gl_state != LM_ST_UNLOCKED && demote_ok(gl))
goto out_schedule;
gfs2_glmutex_unlock(gl);
}
-out:
- gfs2_glock_put(gl);
return;
out_schedule:
gfs2_glmutex_unlock(gl);
gfs2_glock_schedule_for_reclaim(gl);
- gfs2_glock_put(gl);
}
/**
@@ -2014,11 +1986,8 @@ static void clear_glock(struct gfs2_glock *gl)
if (queue_empty(gl, &gl->gl_holders) &&
gl->gl_state != LM_ST_UNLOCKED)
handle_callback(gl, LM_ST_UNLOCKED);
-
gfs2_glmutex_unlock(gl);
}
-
- gfs2_glock_put(gl);
}
/**
@@ -2040,10 +2009,10 @@ void gfs2_gl_hash_clear(struct gfs2_sbd *sdp, int wait)
for (;;) {
cont = 0;
-
- for (x = 0; x < GFS2_GL_HASH_SIZE; x++)
- if (examine_bucket(clear_glock, sdp, x))
+ for (x = 0; x < GFS2_GL_HASH_SIZE; x++) {
+ if (examine_bucket(clear_glock, sdp, x))
cont = 1;
+ }
if (!wait || !cont)
break;
@@ -2234,8 +2203,6 @@ static int gfs2_dump_lockstate(struct gfs2_sbd *sdp)
read_lock(gl_lock_addr(x));
list_for_each_entry(gl, &gl_hash_table[x].hb_list, gl_list) {
- if (test_bit(GLF_PLUG, &gl->gl_flags))
- continue;
if (gl->gl_sbd != sdp)
continue;
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 64e13435ca3..1fed8d1abae 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -152,7 +152,6 @@ struct gfs2_holder {
};
enum {
- GLF_PLUG = 0,
GLF_LOCK = 1,
GLF_STICKY = 2,
GLF_PREFETCH = 3,