[PATCH 09/10] fs/dcache: Add per-sb accounting for nr dentries

[Kent Overstreet <kent.overstreet@linux.dev>]

Like the previous patch, add a counter for total dentries, so we can
print total vs. reclaimable.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/dcache.c        | 2 ++
 fs/super.c         | 6 ++++++
 include/linux/fs.h | 1 +
 3 files changed, 9 insertions(+)

diff --git a/fs/dcache.c b/fs/dcache.c
index 64108cbd52f6..4bbb2c87f824 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -601,6 +601,7 @@ static struct dentry *__dentry_kill(struct dentry *dentry)
 	else
 		spin_unlock(&dentry->d_lock);
 	this_cpu_dec(nr_dentry);
+	this_cpu_dec(*dentry->d_sb->s_dentry_nr);
 	if (dentry->d_op && dentry->d_op->d_release)
 		dentry->d_op->d_release(dentry);
 
@@ -1683,6 +1684,7 @@ static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	}
 
 	this_cpu_inc(nr_dentry);
+	this_cpu_inc(*sb->s_dentry_nr);
 
 	return dentry;
 }
diff --git a/fs/super.c b/fs/super.c
index b1b6ae491b6c..5b0fea6ff1cd 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -278,6 +278,7 @@ static void destroy_super_work(struct work_struct *work)
 	security_sb_free(s);
 	put_user_ns(s->s_user_ns);
 	kfree(s->s_subtype);
+	free_percpu(s->s_dentry_nr);
 	free_percpu(s->s_inodes_nr);
 	for (int i = 0; i < SB_FREEZE_LEVELS; i++)
 		percpu_free_rwsem(&s->s_writers.rw_sem[i]);
@@ -299,6 +300,7 @@ static void destroy_unused_super(struct super_block *s)
 	super_unlock_excl(s);
 	list_lru_destroy(&s->s_dentry_lru);
 	list_lru_destroy(&s->s_inode_lru);
+	free_percpu(s->s_dentry_nr);
 	free_percpu(s->s_inodes_nr);
 	shrinker_free(s->s_shrink);
 	/* no delays needed */
@@ -381,6 +383,10 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	if (!s->s_inodes_nr)
 		goto fail;
 
+	s->s_dentry_nr = alloc_percpu(size_t);
+	if (!s->s_dentry_nr)
+		goto fail;
+
 	s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
 				     "sb-%s", type->name);
 	if (!s->s_shrink)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 86636831b9d0..493fb8e72bf0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1332,6 +1332,7 @@ struct super_block {
 	 * There is no need to put them into separate cachelines.
 	 */
 	struct list_lru		s_dentry_lru;
+	size_t __percpu		*s_dentry_nr;
 	struct list_lru		s_inode_lru;
 	struct rcu_head		rcu;
 	struct work_struct	destroy_work;
-- 
2.45.2