[PATCH 08/10] fs: Add super_block->s_inodes_nr

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

Upcoming shrinker debugging patchset is going to give us a callback for
reporting on all memory owned by a shrinker.

This adds a counter for total number of inodes allocated for a given
superblock, so we can compare with the number of reclaimable inodes we
already have.

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/inode.c         | 2 ++
 fs/super.c         | 7 +++++++
 include/linux/fs.h | 1 +
 3 files changed, 10 insertions(+)

diff --git a/fs/inode.c b/fs/inode.c
index 5e7dcdeedd4d..2650c5ce74e1 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -489,12 +489,14 @@ void inode_sb_list_add(struct inode *inode)
 	spin_lock(&inode->i_sb->s_inode_list_lock);
 	list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
 	spin_unlock(&inode->i_sb->s_inode_list_lock);
+	this_cpu_inc(*inode->i_sb->s_inodes_nr);
 }
 EXPORT_SYMBOL_GPL(inode_sb_list_add);
 
 static inline void inode_sb_list_del(struct inode *inode)
 {
 	if (!list_empty(&inode->i_sb_list)) {
+		this_cpu_dec(*inode->i_sb->s_inodes_nr);
 		spin_lock(&inode->i_sb->s_inode_list_lock);
 		list_del_init(&inode->i_sb_list);
 		spin_unlock(&inode->i_sb->s_inode_list_lock);
diff --git a/fs/super.c b/fs/super.c
index b7913b55debc..b1b6ae491b6c 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_inodes_nr);
 	for (int i = 0; i < SB_FREEZE_LEVELS; i++)
 		percpu_free_rwsem(&s->s_writers.rw_sem[i]);
 	kfree(s);
@@ -298,6 +299,7 @@ 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_inodes_nr);
 	shrinker_free(s->s_shrink);
 	/* no delays needed */
 	destroy_super_work(&s->destroy_work);
@@ -375,6 +377,10 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	s->s_time_min = TIME64_MIN;
 	s->s_time_max = TIME64_MAX;
 
+	s->s_inodes_nr = alloc_percpu(size_t);
+	if (!s->s_inodes_nr)
+		goto fail;
+
 	s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
 				     "sb-%s", type->name);
 	if (!s->s_shrink)
@@ -408,6 +414,7 @@ static void __put_super(struct super_block *s)
 		WARN_ON(s->s_dentry_lru.node);
 		WARN_ON(s->s_inode_lru.node);
 		WARN_ON(!list_empty(&s->s_mounts));
+		WARN_ON(per_cpu_sum(s->s_inodes_nr));
 		call_rcu(&s->rcu, destroy_super_rcu);
 	}
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8fc4bad3b6ae..86636831b9d0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1346,6 +1346,7 @@ struct super_block {
 	/* s_inode_list_lock protects s_inodes */
 	spinlock_t		s_inode_list_lock ____cacheline_aligned_in_smp;
 	struct list_head	s_inodes;	/* all inodes */
+	size_t __percpu		*s_inodes_nr;
 
 	spinlock_t		s_inode_wblist_lock;
 	struct list_head	s_inodes_wb;	/* writeback inodes */
-- 
2.45.2