[PATCH 13/13] vfs: Dentry mobs listing in proc

[Pavel Emelyanov <xemul@parallels.com>]

The /proc/dentry_mobs file lists the device the mob is located on,
the path to the dentry (starting from the device root) its usage and
size.

I tried to make it very simple, as this API is not perfect from my
POV and will most likely be rewritten. For the same reason (simplicity)
the dentry_path is used, not the full path to the root.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---
 fs/dcache.c            |   58 ++++++++++++++++++++++++++++++++++++++++++++++++
 fs/proc/root.c         |    3 ++
 include/linux/dcache.h |    2 +
 3 files changed, 63 insertions(+), 0 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 01e3464..c1120b3 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3028,6 +3028,7 @@ int dcache_new_mob(struct dentry *root)
 	spin_unlock(&root->d_lock);
 
 	spin_lock(&dcache_mobs_lock);
+	dmob->mob_root = root;
 	list_add(&dmob->mobs, &dentry_mobs);
 	dentry_mobs_nr++;
 	spin_unlock(&dcache_mobs_lock);
@@ -3068,6 +3069,63 @@ int dcache_get_mob_stat(struct dentry *de, struct dentry_mob_stat __user *stat)
 	return 0;
 }
 
+static int dentry_mobs_show(struct seq_file *f, void *v)
+{
+	struct dentry_mob *dmob;
+
+	dmob = list_entry(v, struct dentry_mob, mobs);
+	if (dmob == &init_dentry_mob)
+		seq_putc(f, '/');
+	else {
+		struct dentry *root = dmob->mob_root;
+
+		seq_printf(f, "%u:%u ", MAJOR(root->d_sb->s_dev),
+				MINOR(root->d_sb->s_dev));
+		seq_dentry(f, root, " \t\n\\");
+	}
+
+	seq_printf(f, " %lu %lu\n",
+			(unsigned long)percpu_counter_sum_positive(&dmob->nr_dentry),
+			dmob->nr_dentry_max);
+
+	return 0;
+}
+
+static void *dentry_mobs_start(struct seq_file *f, loff_t *pos)
+{
+	spin_lock(&dcache_mobs_lock);
+	return seq_list_start(&dentry_mobs, *pos);
+}
+
+static void *dentry_mobs_next(struct seq_file *f, void *v, loff_t *pos)
+{
+	return seq_list_next(v, &dentry_mobs, pos);
+}
+
+static void dentry_mobs_stop(struct seq_file *f, void *v)
+{
+	spin_unlock(&dcache_mobs_lock);
+}
+
+static const struct seq_operations dentry_mobs_ops = {
+	.start = dentry_mobs_start,
+	.next  = dentry_mobs_next,
+	.stop  = dentry_mobs_stop,
+	.show  = dentry_mobs_show
+};
+
+static int dentry_mobs_open(struct inode *inode, struct file *filp)
+{
+	return seq_open(filp, &dentry_mobs_ops);
+}
+
+const struct file_operations proc_dentry_mobs_fops = {
+	.open		= dentry_mobs_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+};
+
 static __initdata unsigned long dhash_entries;
 static int __init set_dhash_entries(char *str)
 {
diff --git a/fs/proc/root.c b/fs/proc/root.c
index ef9fa8e..e4d4983 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -18,6 +18,7 @@
 #include <linux/bitops.h>
 #include <linux/mount.h>
 #include <linux/pid_namespace.h>
+#include <linux/dcache.h>
 
 #include "internal.h"
 
@@ -133,6 +134,8 @@ void __init proc_root_init(void)
 	proc_device_tree_init();
 #endif
 	proc_mkdir("bus", NULL);
+
+	proc_create("dentry_mobs", S_IRUGO, NULL, &proc_dentry_mobs_fops);
 	proc_sys_init();
 }
 
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 7b1fdc1..8a9a5a5 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -53,6 +53,7 @@ struct dentry_mob {
 	unsigned long nr_dentry_max;
 	struct list_head dentry_lru;
 	struct list_head mobs;
+	struct dentry *mob_root;
 };
 
 struct dentry;
@@ -64,6 +65,7 @@ struct dentry_mob_stat {
 int dcache_new_mob(struct dentry *root);
 int dcache_set_mob_size(struct dentry *de, unsigned long size);
 int dcache_get_mob_stat(struct dentry *de, struct dentry_mob_stat __user *stat);
+extern const struct file_operations proc_dentry_mobs_fops;
 
 /*
  * Compare 2 name strings, return 0 if they match, otherwise non-zero.
-- 
1.5.5.6