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Message-Id: <1314089786-20535-14-git-send-email-david@fromorbit.com>
Date:	Tue, 23 Aug 2011 18:56:26 +1000
From:	Dave Chinner <david@...morbit.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	khlebnikov@...nvz.org
Subject: [PATCH 13/13] dcache: convert to use new lru list infrastructure

From: Dave Chinner <dchinner@...hat.com>

Signed-off-by: Dave Chinner <dchinner@...hat.com>
---
 fs/dcache.c        |  142 +++++++++++++++++++++-------------------------------
 fs/super.c         |   10 ++--
 include/linux/fs.h |   14 +++--
 3 files changed, 71 insertions(+), 95 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 79bf47c..382cd27 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -36,6 +36,7 @@
 #include <linux/bit_spinlock.h>
 #include <linux/rculist_bl.h>
 #include <linux/prefetch.h>
+#include <linux/list_lru.h>
 #include "internal.h"
 
 /*
@@ -239,42 +240,17 @@ static void dentry_unlink_inode(struct dentry * dentry)
  */
 static void dentry_lru_add(struct dentry *dentry)
 {
-	if (list_empty(&dentry->d_lru)) {
-		spin_lock(&dentry->d_sb->s_dentry_lru_lock);
-		list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
-		dentry->d_sb->s_nr_dentry_unused++;
+	if (list_empty(&dentry->d_lru) &&
+	    list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
 		this_cpu_inc(nr_dentry_unused);
-		spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
-	}
 }
 
-static void __dentry_lru_del(struct dentry *dentry)
-{
-	list_del_init(&dentry->d_lru);
-	dentry->d_sb->s_nr_dentry_unused--;
-	this_cpu_dec(nr_dentry_unused);
-}
 
 static void dentry_lru_del(struct dentry *dentry)
 {
-	if (!list_empty(&dentry->d_lru)) {
-		spin_lock(&dentry->d_sb->s_dentry_lru_lock);
-		__dentry_lru_del(dentry);
-		spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
-	}
-}
-
-static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
-{
-	spin_lock(&dentry->d_sb->s_dentry_lru_lock);
-	if (list_empty(&dentry->d_lru)) {
-		list_add_tail(&dentry->d_lru, list);
-	} else {
-		list_move_tail(&dentry->d_lru, list);
-		dentry->d_sb->s_nr_dentry_unused--;
+	if (!list_empty(&dentry->d_lru) &&
+	    list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
 		this_cpu_dec(nr_dentry_unused);
-	}
-	spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
 }
 
 /**
@@ -756,6 +732,50 @@ static void shrink_dentry_list(struct list_head *list)
 	rcu_read_unlock();
 }
 
+static int dentry_lru_isolate(struct list_head *item, spinlock_t *lru_lock,
+				void *arg)
+{
+	struct list_head *freeable = arg;
+	struct dentry	*dentry = container_of(item, struct dentry, d_lru);
+
+
+	/*
+	 * we are inverting the lru lock/dentry->d_lock here,
+	 * so use a trylock. If we fail to get the lock, just skip
+	 * it
+	 */
+	if (!spin_trylock(&dentry->d_lock))
+		return 2;
+
+	/*
+	 * Referenced dentries are still in use. If they have active
+	 * counts, just remove them from the LRU. Otherwise give them
+	 * another pass through the LRU.
+	 */
+	if (dentry->d_count) {
+		list_del_init(&dentry->d_lru);
+		spin_unlock(&dentry->d_lock);
+		return 0;
+	}
+
+	if (dentry->d_flags & DCACHE_REFERENCED) {
+		dentry->d_flags &= ~DCACHE_REFERENCED;
+		spin_unlock(&dentry->d_lock);
+
+		/*
+		 * XXX: this list move should be be done under d_lock. Need to
+		 * determine if it is safe just to do it under the lru lock.
+		 */
+		return 1;
+	}
+
+	list_move_tail(&dentry->d_lru, freeable);
+	this_cpu_dec(nr_dentry_unused);
+	spin_unlock(&dentry->d_lock);
+
+	return 0;
+}
+
 /**
  * prune_dcache_sb - shrink the dcache
  * @sb: superblock
@@ -770,44 +790,13 @@ static void shrink_dentry_list(struct list_head *list)
  */
 long prune_dcache_sb(struct super_block *sb, long nr_to_scan)
 {
-	struct dentry *dentry;
-	LIST_HEAD(referenced);
-	LIST_HEAD(tmp);
+	LIST_HEAD(dispose);
 	long freed = 0;
 
-relock:
-	spin_lock(&sb->s_dentry_lru_lock);
-	while (!list_empty(&sb->s_dentry_lru)) {
-		dentry = list_entry(sb->s_dentry_lru.prev,
-				struct dentry, d_lru);
-		BUG_ON(dentry->d_sb != sb);
-
-		if (!spin_trylock(&dentry->d_lock)) {
-			spin_unlock(&sb->s_dentry_lru_lock);
-			cpu_relax();
-			goto relock;
-		}
+	freed = list_lru_walk(&sb->s_dentry_lru, dentry_lru_isolate,
+			      &dispose, nr_to_scan);
 
-		if (dentry->d_flags & DCACHE_REFERENCED) {
-			dentry->d_flags &= ~DCACHE_REFERENCED;
-			list_move(&dentry->d_lru, &referenced);
-			spin_unlock(&dentry->d_lock);
-		} else {
-			list_move_tail(&dentry->d_lru, &tmp);
-			this_cpu_dec(nr_dentry_unused);
-			sb->s_nr_dentry_unused--;
-			spin_unlock(&dentry->d_lock);
-			freed++;
-			if (!--nr_to_scan)
-				break;
-		}
-		cond_resched_lock(&sb->s_dentry_lru_lock);
-	}
-	if (!list_empty(&referenced))
-		list_splice(&referenced, &sb->s_dentry_lru);
-	spin_unlock(&sb->s_dentry_lru_lock);
-
-	shrink_dentry_list(&tmp);
+	shrink_dentry_list(&dispose);
 	return freed;
 }
 
@@ -820,24 +809,10 @@ relock:
  */
 void shrink_dcache_sb(struct super_block *sb)
 {
-	LIST_HEAD(tmp);
-
-	spin_lock(&sb->s_dentry_lru_lock);
-	while (!list_empty(&sb->s_dentry_lru)) {
-		list_splice_init(&sb->s_dentry_lru, &tmp);
+	long freed;
 
-		/*
-		 * account for removal here so we don't need to handle it later
-		 * even though the dentry is no longer on the lru list.
-		 */
-		this_cpu_sub(nr_dentry_unused, sb->s_nr_dentry_unused);
-		sb->s_nr_dentry_unused = 0;
-
-		spin_unlock(&sb->s_dentry_lru_lock);
-		shrink_dentry_list(&tmp);
-		spin_lock(&sb->s_dentry_lru_lock);
-	}
-	spin_unlock(&sb->s_dentry_lru_lock);
+	freed = list_lru_dispose_all(&sb->s_dentry_lru, shrink_dentry_list);
+	this_cpu_sub(nr_dentry_unused, freed);
 }
 EXPORT_SYMBOL(shrink_dcache_sb);
 
@@ -1094,11 +1069,10 @@ resume:
 		/*
 		 * move only zero ref count dentries to the dispose list.
 		 */
+		dentry_lru_del(dentry);
 		if (!dentry->d_count) {
-			dentry_lru_move_list(dentry, dispose);
+			list_add_tail(&dentry->d_lru, dispose);
 			found++;
-		} else {
-			dentry_lru_del(dentry);
 		}
 
 		/*
diff --git a/fs/super.c b/fs/super.c
index bc0e101..cc96fdf 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -70,10 +70,11 @@ static long super_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
 		fs_objects = sb->s_op->nr_cached_objects(sb);
 
 	inodes = list_lru_count(&sb->s_inode_lru);
-	total_objects = sb->s_nr_dentry_unused + inodes + fs_objects + 1;
+	dentries = list_lru_count(&sb->s_dentry_lru);
+	total_objects = dentries + inodes + fs_objects + 1;
 
 	/* proportion the scan between the caches */
-	dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / total_objects;
+	dentries = (sc->nr_to_scan * dentries) / total_objects;
 	inodes = (sc->nr_to_scan * inodes) / total_objects;
 
 	/*
@@ -105,7 +106,7 @@ static long super_cache_count(struct shrinker *shrink, struct shrink_control *sc
 	if (sb->s_op && sb->s_op->nr_cached_objects)
 		total_objects = sb->s_op->nr_cached_objects(sb);
 
-	total_objects += sb->s_nr_dentry_unused;
+	total_objects += list_lru_count(&sb->s_dentry_lru);
 	total_objects += list_lru_count(&sb->s_inode_lru);
 
 	total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
@@ -151,8 +152,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
 		INIT_LIST_HEAD(&s->s_instances);
 		INIT_HLIST_BL_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
-		INIT_LIST_HEAD(&s->s_dentry_lru);
-		spin_lock_init(&s->s_dentry_lru_lock);
+		list_lru_init(&s->s_dentry_lru);
 		list_lru_init(&s->s_inode_lru);
 		init_rwsem(&s->s_umount);
 		mutex_init(&s->s_lock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 80beb62..fd458f9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1411,12 +1411,6 @@ struct super_block {
 #else
 	struct list_head	s_files;
 #endif
-	spinlock_t		s_dentry_lru_lock ____cacheline_aligned_in_smp;
-	struct list_head	s_dentry_lru;	/* unused dentry lru */
-	int			s_nr_dentry_unused; /* # of dentries on lru */
-
-	struct list_lru		s_inode_lru ____cacheline_aligned_in_smp;
-
 	struct block_device	*s_bdev;
 	struct backing_dev_info *s_bdi;
 	struct mtd_info		*s_mtd;
@@ -1461,6 +1455,14 @@ struct super_block {
 	int cleancache_poolid;
 
 	struct shrinker s_shrink;	/* per-sb shrinker handle */
+
+	/*
+	 * keep the lru lists last in the structure so they always sit on their
+	 * own individual cachelines.
+	 */
+	struct list_lru		s_dentry_lru ____cacheline_aligned_in_smp;
+	struct list_lru		s_inode_lru ____cacheline_aligned_in_smp;
+
 };
 
 extern struct timespec current_fs_time(struct super_block *sb);
-- 
1.7.5.4

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