Commit cec59c44 authored by Jinliang Zheng's avatar Jinliang Zheng Committed by Greg Kroah-Hartman
Browse files

kernfs: switch global kernfs_idr_lock to per-fs lock 



The kernfs implementation has big lock granularity(kernfs_idr_lock) so
every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the lock.

This patch switches the global kernfs_idr_lock to per-fs lock, which
put the spinlock into kernfs_root.

Signed-off-by: default avatarJinliang Zheng <alexjlzheng@tencent.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20250415153659.14950-2-alexjlzheng@tencent.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2806c6b8

fs/kernfs/dir.c

+7 −7
Original line number Diff line number Diff line
@@ -27,7 +27,6 @@ DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->name */ 
 */

static DEFINE_SPINLOCK(kernfs_pr_cont_lock);

static char kernfs_pr_cont_buf[PATH_MAX];	/* protected by pr_cont_lock */

static DEFINE_SPINLOCK(kernfs_idr_lock);	/* root->ino_idr */



#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
@@ -584,9 +583,9 @@ void kernfs_put(struct kernfs_node *kn) 
	if (kernfs_type(kn) == KERNFS_LINK)

		kernfs_put(kn->symlink.target_kn);



	spin_lock(&kernfs_idr_lock);

	spin_lock(&root->kernfs_idr_lock);

	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));

	spin_unlock(&kernfs_idr_lock);

	spin_unlock(&root->kernfs_idr_lock);



	call_rcu(&kn->rcu, kernfs_free_rcu);
@@ -639,13 +638,13 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root, 
		goto err_out1;



	idr_preload(GFP_KERNEL);

	spin_lock(&kernfs_idr_lock);

	spin_lock(&root->kernfs_idr_lock);

	ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);

	if (ret >= 0 && ret < root->last_id_lowbits)

		root->id_highbits++;

	id_highbits = root->id_highbits;

	root->last_id_lowbits = ret;

	spin_unlock(&kernfs_idr_lock);

	spin_unlock(&root->kernfs_idr_lock);

	idr_preload_end();

	if (ret < 0)

		goto err_out2;
@@ -681,9 +680,9 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root, 
	return kn;



 err_out3:

	spin_lock(&kernfs_idr_lock);

	spin_lock(&root->kernfs_idr_lock);

	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));

	spin_unlock(&kernfs_idr_lock);

	spin_unlock(&root->kernfs_idr_lock);

 err_out2:

	kmem_cache_free(kernfs_node_cache, kn);

 err_out1:
@@ -989,6 +988,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, 
		return ERR_PTR(-ENOMEM);



	idr_init(&root->ino_idr);

	spin_lock_init(&root->kernfs_idr_lock);

	init_rwsem(&root->kernfs_rwsem);

	init_rwsem(&root->kernfs_iattr_rwsem);

	init_rwsem(&root->kernfs_supers_rwsem);

fs/kernfs/kernfs-internal.h

+1 −0
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ struct kernfs_root { 


	/* private fields, do not use outside kernfs proper */

	struct idr		ino_idr;

	spinlock_t		kernfs_idr_lock;	/* root->ino_idr */

	u32			last_id_lowbits;

	u32			id_highbits;

	struct kernfs_syscall_ops *syscall_ops;