sysfs, kernfs: implement kernfs_ns_enabled()

fs/sysfs/symlink.c::sysfs_delete_link() tests @sd->s_flags for
SYSFS_FLAG_NS.  Let's add kernfs_ns_enabled() so that sysfs doesn't
have to test sysfs_dirent flag directly.  This makes things tidier for
kernfs proper too.

This is purely cosmetic.

v2: To avoid possible NULL deref, use noop dummy implementation which
    always returns false when !CONFIG_SYSFS.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 6 insertions, 6 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 7c5b51793689..f51e0625e666 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -291,7 +291,7 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, unsigned int flags)
                 goto out_bad;
 
         /* The sysfs dirent has been moved to a different namespace */
-        if (sd->s_parent && (sd->s_parent->s_flags & SYSFS_FLAG_NS) &&
+        if (sd->s_parent && kernfs_ns_enabled(sd->s_parent) &&
             sysfs_info(dentry->d_sb)->ns != sd->s_ns)
                 goto out_bad;
 
@@ -414,7 +414,7 @@ void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt)
 int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd,
                   struct sysfs_dirent *parent_sd)
 {
-        bool has_ns = parent_sd->s_flags & SYSFS_FLAG_NS;
+        bool has_ns = kernfs_ns_enabled(parent_sd);
         struct sysfs_inode_attrs *ps_iattr;
         int ret;
 
@@ -535,7 +535,7 @@ static struct sysfs_dirent *kernfs_find_ns(struct sysfs_dirent *parent,
                                            const void *ns)
 {
         struct rb_node *node = parent->s_dir.children.rb_node;
-        bool has_ns = parent->s_flags & SYSFS_FLAG_NS;
+        bool has_ns = kernfs_ns_enabled(parent);
         unsigned int hash;
 
         lockdep_assert_held(&sysfs_mutex);
@@ -685,7 +685,7 @@ static struct dentry *sysfs_lookup(struct inode *dir, struct dentry *dentry,
 
         mutex_lock(&sysfs_mutex);
 
-        if (parent_sd->s_flags & SYSFS_FLAG_NS)
+        if (kernfs_ns_enabled(parent_sd))
                 ns = sysfs_info(dir->i_sb)->ns;
 
         sd = kernfs_find_ns(parent_sd, dentry->d_name.name, ns);
@@ -968,7 +968,7 @@ static int sysfs_readdir(struct file *file, struct dir_context *ctx)
                 return 0;
         mutex_lock(&sysfs_mutex);
 
-        if (parent_sd->s_flags & SYSFS_FLAG_NS)
+        if (kernfs_ns_enabled(parent_sd))
                 ns = sysfs_info(dentry->d_sb)->ns;
 
         for (pos = sysfs_dir_pos(ns, parent_sd, ctx->pos, pos);
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 004c16465594..12569a738837 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -35,7 +35,7 @@ struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
         if (!sd)
                 return ERR_PTR(-ENOMEM);
 
-        if (parent->s_flags & SYSFS_FLAG_NS)
+        if (kernfs_ns_enabled(parent))
                 sd->s_ns = target->s_ns;
         sd->s_symlink.target_sd = target;
         kernfs_get(target);     /* ref owned by symlink */