[PATCH v6 7/7] kernfs: Replace per-fs rwsem with hashed ones.

From: Imran Khan
Date: Mon Feb 14 2022 - 07:04:27 EST

Remove per-fs rwsem, using hashed rwsem and corresponding interface
introduced in previous patch. Also as we are removing use of per-fs
rwsem, we no longer need lockdep checkings under kernfs_active.
Wherever needed lockdep checkings can be made on a per-node basis using
interfaces provided in previous patch.

Signed-off-by: Imran Khan <imran.f.khan@xxxxxxxxxx>
---
fs/kernfs/dir.c | 130 ++++++++++++++++++------------------
fs/kernfs/file.c | 4 +-
fs/kernfs/inode.c | 22 +++---
fs/kernfs/kernfs-internal.h | 1 -
fs/kernfs/mount.c | 5 +-
fs/kernfs/symlink.c | 5 +-
6 files changed, 80 insertions(+), 87 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 0dac58f8091c9..42404f8bc6acd 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -449,21 +449,22 @@ void kernfs_put_active(struct kernfs_node *kn)
/**
* kernfs_drain - drain kernfs_node
* @kn: kernfs_node to drain
+ * @anc: ancestor of kernfs_node to drain
*
* Drain existing usages and nuke all existing mmaps of @kn. Mutiple
* removers may invoke this function concurrently on @kn and all will
* return after draining is complete.
*/
-static void kernfs_drain(struct kernfs_node *kn)
- __releases(&kernfs_root(kn)->kernfs_rwsem)
- __acquires(&kernfs_root(kn)->kernfs_rwsem)
+static void kernfs_drain(struct kernfs_node *kn, struct kernfs_node *anc)
+ __releases(kernfs_rwsem_ptr(anc))
+ __acquires(kernfs_rwsem_ptr(anc))
{
struct kernfs_root *root = kernfs_root(kn);

- lockdep_assert_held_write(&root->kernfs_rwsem);
+ kernfs_rwsem_assert_held_write(anc);
WARN_ON_ONCE(kernfs_active(kn));

- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(anc);

if (kernfs_lockdep(kn)) {
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
@@ -482,7 +483,7 @@ static void kernfs_drain(struct kernfs_node *kn)

kernfs_drain_open_files(kn);

- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(anc, KERNFS_RWSEM_LOCK_SELF);
}

/**
@@ -717,12 +718,16 @@ struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
int kernfs_add_one(struct kernfs_node *kn)
{
struct kernfs_node *parent = kn->parent;
- struct kernfs_root *root = kernfs_root(parent);
struct kernfs_iattrs *ps_iattr;
bool has_ns;
int ret;

- down_write(&root->kernfs_rwsem);
+ /**
+ * The node being added is not active at this point of time and may
+ * be activated later depending on CREATE_DEACTIVATED flag. So at
+ * this point of time just locking the parent is enough.
+ */
+ down_write_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);

ret = -EINVAL;
has_ns = kernfs_ns_enabled(parent);
@@ -753,7 +758,7 @@ int kernfs_add_one(struct kernfs_node *kn)
ps_iattr->ia_mtime = ps_iattr->ia_ctime;
}

- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(parent);

/*
* Activate the new node unless CREATE_DEACTIVATED is requested.
@@ -767,7 +772,7 @@ int kernfs_add_one(struct kernfs_node *kn)
return 0;

out_unlock:
- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(parent);
return ret;
}

@@ -788,7 +793,7 @@ static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
bool has_ns = kernfs_ns_enabled(parent);
unsigned int hash;

- lockdep_assert_held(&kernfs_root(parent)->kernfs_rwsem);
+ kernfs_rwsem_assert_held(parent);

if (has_ns != (bool)ns) {
WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
@@ -820,7 +825,7 @@ static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
size_t len;
char *p, *name;

- lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem);
+ kernfs_rwsem_assert_held_read(parent);

/* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */
spin_lock_irq(&kernfs_rename_lock);
@@ -859,12 +864,11 @@ struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
const char *name, const void *ns)
{
struct kernfs_node *kn;
- struct kernfs_root *root = kernfs_root(parent);

- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);
kn = kernfs_find_ns(parent, name, ns);
kernfs_get(kn);
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);

return kn;
}
@@ -884,12 +888,11 @@ struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
const char *path, const void *ns)
{
struct kernfs_node *kn;
- struct kernfs_root *root = kernfs_root(parent);

- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);
kn = kernfs_walk_ns(parent, path, ns);
kernfs_get(kn);
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);

return kn;
}
@@ -914,7 +917,6 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
return ERR_PTR(-ENOMEM);

idr_init(&root->ino_idr);
- init_rwsem(&root->kernfs_rwsem);
INIT_LIST_HEAD(&root->supers);
init_rwsem(&root->supers_rwsem);

@@ -1045,7 +1047,6 @@ struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
{
struct kernfs_node *kn;
- struct kernfs_root *root;

if (flags & LOOKUP_RCU)
return -ECHILD;
@@ -1061,13 +1062,12 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
parent = kernfs_dentry_node(dentry->d_parent);
if (parent) {
spin_unlock(&dentry->d_lock);
- root = kernfs_root(parent);
- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);
if (kernfs_dir_changed(parent, dentry)) {
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);
return 0;
}
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);
} else
spin_unlock(&dentry->d_lock);

@@ -1078,8 +1078,7 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
}

kn = kernfs_dentry_node(dentry);
- root = kernfs_root(kn);
- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);

/* The kernfs node has been deactivated */
if (!kernfs_active(kn))
@@ -1098,10 +1097,10 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
kernfs_info(dentry->d_sb)->ns != kn->ns)
goto out_bad;

- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(kn);
return 1;
out_bad:
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(kn);
return 0;
}

@@ -1115,28 +1114,29 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
{
struct kernfs_node *parent = dir->i_private;
struct kernfs_node *kn;
- struct kernfs_root *root;
struct inode *inode = NULL;
const void *ns = NULL;

- root = kernfs_root(parent);
- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);
if (kernfs_ns_enabled(parent))
ns = kernfs_info(dir->i_sb)->ns;

kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
+ up_read_kernfs_rwsem(parent);
/* attach dentry and inode */
if (kn) {
/* Inactive nodes are invisible to the VFS so don't
* create a negative.
*/
+ down_read_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
if (!kernfs_active(kn)) {
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(kn);
return NULL;
}
inode = kernfs_get_inode(dir->i_sb, kn);
if (!inode)
inode = ERR_PTR(-ENOMEM);
+ up_read_kernfs_rwsem(kn);
}
/*
* Needed for negative dentry validation.
@@ -1144,9 +1144,10 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
* or transforms from positive dentry in dentry_unlink_inode()
* called from vfs_rmdir().
*/
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);
if (!IS_ERR(inode))
kernfs_set_rev(parent, dentry);
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);

/* instantiate and hash (possibly negative) dentry */
return d_splice_alias(inode, dentry);
@@ -1269,7 +1270,7 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
{
struct rb_node *rbn;

- lockdep_assert_held_write(&kernfs_root(root)->kernfs_rwsem);
+ kernfs_rwsem_assert_held_write(root);

/* if first iteration, visit leftmost descendant which may be root */
if (!pos)
@@ -1304,9 +1305,8 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
void kernfs_activate(struct kernfs_node *kn)
{
struct kernfs_node *pos;
- struct kernfs_root *root = kernfs_root(kn);

- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);

pos = NULL;
while ((pos = kernfs_next_descendant_post(pos, kn))) {
@@ -1320,15 +1320,13 @@ void kernfs_activate(struct kernfs_node *kn)
pos->flags |= KERNFS_ACTIVATED;
}

- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(kn);
}

static void __kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_node *pos;

- lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem);
-
/*
* Short-circuit if non-root @kn has already finished removal.
* This is for kernfs_remove_self() which plays with active ref
@@ -1341,12 +1339,16 @@ static void __kernfs_remove(struct kernfs_node *kn)

/* prevent any new usage under @kn by deactivating all nodes */
pos = NULL;
+
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
while ((pos = kernfs_next_descendant_post(pos, kn)))
if (kernfs_active(pos))
atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
+ up_write_kernfs_rwsem(kn);

/* deactivate and unlink the subtree node-by-node */
do {
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
pos = kernfs_leftmost_descendant(kn);

/*
@@ -1364,10 +1366,15 @@ static void __kernfs_remove(struct kernfs_node *kn)
* error paths without worrying about draining.
*/
if (kn->flags & KERNFS_ACTIVATED)
- kernfs_drain(pos);
+ kernfs_drain(pos, kn);
else
WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);

+ up_write_kernfs_rwsem(kn);
+
+ if (pos->parent)
+ down_write_kernfs_rwsem(pos->parent, KERNFS_RWSEM_LOCK_SELF);
+
/*
* kernfs_unlink_sibling() succeeds once per node. Use it
* to decide who's responsible for cleanups.
@@ -1385,6 +1392,9 @@ static void __kernfs_remove(struct kernfs_node *kn)
kernfs_put(pos);
}

+ if (pos->parent)
+ up_write_kernfs_rwsem(pos->parent);
+
kernfs_put(pos);
} while (pos != kn);
}
@@ -1397,11 +1407,7 @@ static void __kernfs_remove(struct kernfs_node *kn)
*/
void kernfs_remove(struct kernfs_node *kn)
{
- struct kernfs_root *root = kernfs_root(kn);
-
- down_write(&root->kernfs_rwsem);
__kernfs_remove(kn);
- up_write(&root->kernfs_rwsem);
}

/**
@@ -1487,9 +1493,8 @@ void kernfs_unbreak_active_protection(struct kernfs_node *kn)
bool kernfs_remove_self(struct kernfs_node *kn)
{
bool ret;
- struct kernfs_root *root = kernfs_root(kn);

- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
kernfs_break_active_protection(kn);

/*
@@ -1503,9 +1508,11 @@ bool kernfs_remove_self(struct kernfs_node *kn)
*/
if (!(kn->flags & KERNFS_SUICIDAL)) {
kn->flags |= KERNFS_SUICIDAL;
+ up_write_kernfs_rwsem(kn);
__kernfs_remove(kn);
kn->flags |= KERNFS_SUICIDED;
ret = true;
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
} else {
wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
DEFINE_WAIT(wait);
@@ -1517,9 +1524,9 @@ bool kernfs_remove_self(struct kernfs_node *kn)
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
break;

- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(kn);
schedule();
- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF_AND_PARENT);
}
finish_wait(waitq, &wait);
WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
@@ -1532,7 +1539,7 @@ bool kernfs_remove_self(struct kernfs_node *kn)
*/
kernfs_unbreak_active_protection(kn);

- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(kn);
return ret;
}

@@ -1549,7 +1556,6 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{
struct kernfs_node *kn;
- struct kernfs_root *root;

if (!parent) {
WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
@@ -1557,15 +1563,15 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
return -ENOENT;
}

- root = kernfs_root(parent);
- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);

kn = kernfs_find_ns(parent, name, ns);
+
+ up_write_kernfs_rwsem(parent);
+
if (kn)
__kernfs_remove(kn);

- up_write(&root->kernfs_rwsem);
-
if (kn)
return 0;
else
@@ -1583,7 +1589,6 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
const char *new_name, const void *new_ns)
{
struct kernfs_node *old_parent;
- struct kernfs_root *root;
const char *old_name = NULL;
int error;

@@ -1591,8 +1596,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
if (!kn->parent)
return -EINVAL;

- root = kernfs_root(kn);
- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem_rename_ns(kn, kn->parent, new_parent);

error = -ENOENT;
if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
@@ -1646,7 +1650,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,

error = 0;
out:
- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
return error;
}

@@ -1717,14 +1721,12 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
struct dentry *dentry = file->f_path.dentry;
struct kernfs_node *parent = kernfs_dentry_node(dentry);
struct kernfs_node *pos = file->private_data;
- struct kernfs_root *root;
const void *ns = NULL;

if (!dir_emit_dots(file, ctx))
return 0;

- root = kernfs_root(parent);
- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);

if (kernfs_ns_enabled(parent))
ns = kernfs_info(dentry->d_sb)->ns;
@@ -1741,12 +1743,12 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
file->private_data = pos;
kernfs_get(pos);

- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);
if (!dir_emit(ctx, name, len, ino, type))
return 0;
- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);
}
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);
file->private_data = NULL;
ctx->pos = INT_MAX;
return 0;
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index af2046bc63aa1..03d8f0d087cb8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -857,7 +857,7 @@ static void kernfs_notify_workfn(struct work_struct *work)

root = kernfs_root(kn);
/* kick fsnotify */
- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);

down_write(&root->supers_rwsem);
list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
@@ -897,7 +897,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
}
up_write(&root->supers_rwsem);

- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(kn);
kernfs_put(kn);
goto repeat;
}
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 3d783d80f5daa..4de65f9c21d85 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -99,11 +99,10 @@ int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
{
int ret;
- struct kernfs_root *root = kernfs_root(kn);

- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
ret = __kernfs_setattr(kn, iattr);
- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(kn);
return ret;
}

@@ -112,14 +111,12 @@ int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
{
struct inode *inode = d_inode(dentry);
struct kernfs_node *kn = inode->i_private;
- struct kernfs_root *root;
int error;

if (!kn)
return -EINVAL;

- root = kernfs_root(kn);
- down_write(&root->kernfs_rwsem);
+ down_write_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
error = setattr_prepare(&init_user_ns, dentry, iattr);
if (error)
goto out;
@@ -132,7 +129,7 @@ int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
setattr_copy(&init_user_ns, inode, iattr);

out:
- up_write(&root->kernfs_rwsem);
+ up_write_kernfs_rwsem(kn);
return error;
}

@@ -187,14 +184,13 @@ int kernfs_iop_getattr(struct user_namespace *mnt_userns,
{
struct inode *inode = d_inode(path->dentry);
struct kernfs_node *kn = inode->i_private;
- struct kernfs_root *root = kernfs_root(kn);

- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
spin_lock(&inode->i_lock);
kernfs_refresh_inode(kn, inode);
generic_fillattr(&init_user_ns, inode, stat);
spin_unlock(&inode->i_lock);
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(kn);

return 0;
}
@@ -278,21 +274,19 @@ int kernfs_iop_permission(struct user_namespace *mnt_userns,
struct inode *inode, int mask)
{
struct kernfs_node *kn;
- struct kernfs_root *root;
int ret;

if (mask & MAY_NOT_BLOCK)
return -ECHILD;

kn = inode->i_private;
- root = kernfs_root(kn);

- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(kn, KERNFS_RWSEM_LOCK_SELF);
spin_lock(&inode->i_lock);
kernfs_refresh_inode(kn, inode);
ret = generic_permission(&init_user_ns, inode, mask);
spin_unlock(&inode->i_lock);
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(kn);

return ret;
}
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index ba89de378f240..f19b180557559 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -133,7 +133,6 @@ int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
/*
* dir.c
*/
-extern struct rw_semaphore kernfs_rwsem;
extern const struct dentry_operations kernfs_dops;
extern const struct file_operations kernfs_dir_fops;
extern const struct inode_operations kernfs_dir_iops;
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index d28f8a3eeb215..2816750f798e2 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -237,7 +237,6 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
{
struct kernfs_super_info *info = kernfs_info(sb);
- struct kernfs_root *kf_root = kfc->root;
struct inode *inode;
struct dentry *root;

@@ -257,9 +256,9 @@ static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *k
sb->s_shrink.seeks = 0;

/* get root inode, initialize and unlock it */
- down_read(&kf_root->kernfs_rwsem);
+ down_read_kernfs_rwsem(info->root->kn, KERNFS_RWSEM_LOCK_SELF);
inode = kernfs_get_inode(sb, info->root->kn);
- up_read(&kf_root->kernfs_rwsem);
+ up_read_kernfs_rwsem(info->root->kn);
if (!inode) {
pr_debug("kernfs: could not get root inode\n");
return -ENOMEM;
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 0ab13824822f7..24d0f64460bda 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -113,12 +113,11 @@ static int kernfs_getlink(struct inode *inode, char *path)
struct kernfs_node *kn = inode->i_private;
struct kernfs_node *parent = kn->parent;
struct kernfs_node *target = kn->symlink.target_kn;
- struct kernfs_root *root = kernfs_root(parent);
int error;

- down_read(&root->kernfs_rwsem);
+ down_read_kernfs_rwsem(parent, KERNFS_RWSEM_LOCK_SELF);
error = kernfs_get_target_path(parent, target, path);
- up_read(&root->kernfs_rwsem);
+ up_read_kernfs_rwsem(parent);

return error;
}
--
2.30.2