[PATCH 11/13] vfs: Make shrink_dcache_memory prune dcache from all mobs

[Pavel Emelyanov <xemul@xxxxxxxxxxxxx>]

For that the list of mobs and their number is introduced. When the
shrink_dcache_memory is called it will srhrink dcache from each
mob in the system.

By now I shrink equal count of dentries from each mob, but I'm open
for discussions of better policies.

Signed-off-by: Pavel Emelyanov <xemul@xxxxxxxxxx>

---
 fs/dcache.c            |   35 ++++++++++++++++++++++++++++++++++-
 include/linux/dcache.h |    1 +
 2 files changed, 35 insertions(+), 1 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index bdacea3..01e3464 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -124,6 +124,9 @@ struct dentry_stat_t dentry_stat = {
 };
 
 static struct dentry_mob init_dentry_mob;
+static LIST_HEAD(dentry_mobs);
+static unsigned int dentry_mobs_nr = 1;
+static DEFINE_SPINLOCK(dcache_mobs_lock);
 
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
 int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
@@ -889,6 +892,25 @@ relock:
 	return shrink_dentry_list(&tmp);
 }
 
+static void prune_dcache_mobs(int nr)
+{
+	int nr_per_mob;
+	struct dentry_mob *mob;
+
+	nr_per_mob = nr / dentry_mobs_nr;
+	if (nr_per_mob == 0)
+		nr_per_mob = 16;
+
+	while (nr--) {
+		spin_lock(&dcache_mobs_lock);
+		mob = list_first_entry(&dentry_mobs, struct dentry_mob, mobs);
+		list_move_tail(&mob->mobs, &dentry_mobs);
+		spin_unlock(&dcache_mobs_lock);
+
+		prune_dcache(mob, nr_per_mob);
+	}
+}
+
 /**
  * shrink_dcache_sb - shrink dcache for a superblock
  * @sb: superblock
@@ -1063,7 +1085,7 @@ static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
 	if (nr) {
 		if (!(gfp_mask & __GFP_FS))
 			return -1;
-		prune_dcache(&init_dentry_mob, nr);
+		prune_dcache_mobs(nr);
 	}
 
 	return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
@@ -2874,6 +2896,11 @@ static struct dentry_mob *create_mob(struct dentry_mob *cur)
 
 static void destroy_mob(struct dentry_mob *mob)
 {
+	spin_lock(&dcache_mobs_lock);
+	list_del(&mob->mobs);
+	dentry_mobs_nr--;
+	spin_unlock(&dcache_mobs_lock);
+
 	if (percpu_counter_sum(&mob->nr_dentry) != 0)
 		BUG();
 	if (!list_empty(&mob->dentry_lru))
@@ -3000,6 +3027,11 @@ int dcache_new_mob(struct dentry *root)
 	percpu_counter_inc(&dmob->nr_dentry);
 	spin_unlock(&root->d_lock);
 
+	spin_lock(&dcache_mobs_lock);
+	list_add(&dmob->mobs, &dentry_mobs);
+	dentry_mobs_nr++;
+	spin_unlock(&dcache_mobs_lock);
+
 	if (old != NULL)
 		destroy_mob(old);
 
@@ -3077,6 +3109,7 @@ static void __init dcache_init(void)
 	percpu_counter_init(&init_dentry_mob.nr_dentry, 0);
 	init_dentry_mob.nr_dentry_max = 80 * 1024 * 1024 / sizeof(struct dentry);
 	INIT_LIST_HEAD(&init_dentry_mob.dentry_lru);
+	list_add_tail(&init_dentry_mob.mobs, &dentry_mobs);
 
 	printk("nr_dentry_max = %lu\n", init_dentry_mob.nr_dentry_max);
 
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 0d13966..7b1fdc1 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -52,6 +52,7 @@ struct dentry_mob {
 	struct percpu_counter nr_dentry;
 	unsigned long nr_dentry_max;
 	struct list_head dentry_lru;
+	struct list_head mobs;
 };
 
 struct dentry;
-- 
1.5.5.6
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