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>

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 7c5b517..f51e062 100644 (file)
--- 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 004c164..12569a7 100644 (file)
--- 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 */

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index 62f0e01..1b8c9ed 100644 (file)
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -128,7 +128,7 @@ void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
         * sysfs_remove_dir() for details.
         */
        spin_lock(&sysfs_symlink_target_lock);
-       if (targ->sd && (kobj->sd->s_flags & SYSFS_FLAG_NS))
+       if (targ->sd && kernfs_ns_enabled(kobj->sd))
                ns = targ->sd->s_ns;
        spin_unlock(&sysfs_symlink_target_lock);
        kernfs_remove_by_name_ns(kobj->sd, name, ns);

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index faaf4f2..d655413 100644 (file)
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -190,6 +190,17 @@ static inline void kernfs_enable_ns(struct sysfs_dirent *sd)
        sd->s_flags |= SYSFS_FLAG_NS;
 }
 
+/**
+ * kernfs_ns_enabled - test whether namespace is enabled
+ * @sd: the node to test
+ *
+ * Test whether namespace filtering is enabled for the children of @ns.
+ */
+static inline bool kernfs_ns_enabled(struct sysfs_dirent *sd)
+{
+       return sd->s_flags & SYSFS_FLAG_NS;
+}
+
 struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent,
                                            const char *name, const void *ns);
 void kernfs_get(struct sysfs_dirent *sd);
@@ -232,6 +243,9 @@ static inline enum kernfs_node_type sysfs_type(struct sysfs_dirent *sd)
 
 static inline void kernfs_enable_ns(struct sysfs_dirent *sd) { }
 
+static inline bool kernfs_ns_enabled(struct sysfs_dirent *sd)
+{ return false; }
+
 static inline struct sysfs_dirent *
 kernfs_find_and_get_ns(struct sysfs_dirent *parent, const char *name,
                       const void *ns)