Introduce kernfs setattr interface - kernfs_setattr().

sysfs_sd_setattr() is renamed to __kernfs_setattr() and
kernfs_setattr() is a simple wrapper around it with sysfs_mutex
locking.  sysfs_chmod_file() is updated to get an explicit ref on
kobj->sd and then invoke kernfs_setattr() so that it doesn't have to
use internal interface.

This patch doesn't introduce any behavior differences.

Signed-off-by: Tejun Heo <t...@kernel.org>
---
 fs/sysfs/file.c        | 13 +++++--------
 fs/sysfs/inode.c       | 21 +++++++++++++++++++--
 fs/sysfs/sysfs.h       |  1 -
 include/linux/kernfs.h |  8 ++++++++
 4 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 6e9c92e..d4eeb50 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -923,19 +923,16 @@ int sysfs_chmod_file(struct kobject *kobj, const struct 
attribute *attr,
        struct iattr newattrs;
        int rc;
 
-       mutex_lock(&sysfs_mutex);
-
-       rc = -ENOENT;
-       sd = sysfs_find_dirent(kobj->sd, attr->name, NULL);
+       sd = sysfs_get_dirent(kobj->sd, attr->name);
        if (!sd)
-               goto out;
+               return -ENOENT;
 
        newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
        newattrs.ia_valid = ATTR_MODE;
-       rc = sysfs_sd_setattr(sd, &newattrs);
 
- out:
-       mutex_unlock(&sysfs_mutex);
+       rc = kernfs_setattr(sd, &newattrs);
+
+       sysfs_put(sd);
        return rc;
 }
 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 1750f79..5f7e2af 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -67,7 +67,7 @@ static struct sysfs_inode_attrs 
*sysfs_init_inode_attrs(struct sysfs_dirent *sd)
        return attrs;
 }
 
-int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr *iattr)
+static int __kernfs_setattr(struct sysfs_dirent *sd, const struct iattr *iattr)
 {
        struct sysfs_inode_attrs *sd_attrs;
        struct iattr *iattrs;
@@ -102,6 +102,23 @@ int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr 
*iattr)
        return 0;
 }
 
+/**
+ * kernfs_setattr - set iattr on a node
+ * @sd: target node
+ * @iattr: iattr to set
+ *
+ * Returns 0 on success, -errno on failure.
+ */
+int kernfs_setattr(struct sysfs_dirent *sd, const struct iattr *iattr)
+{
+       int ret;
+
+       mutex_lock(&sysfs_mutex);
+       ret = __kernfs_setattr(sd, iattr);
+       mutex_unlock(&sysfs_mutex);
+       return ret;
+}
+
 int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
 {
        struct inode *inode = dentry->d_inode;
@@ -116,7 +133,7 @@ int sysfs_setattr(struct dentry *dentry, struct iattr 
*iattr)
        if (error)
                goto out;
 
-       error = sysfs_sd_setattr(sd, iattr);
+       error = __kernfs_setattr(sd, iattr);
        if (error)
                goto out;
 
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 3d48445..d49399d 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -207,7 +207,6 @@ static inline void __sysfs_put(struct sysfs_dirent *sd)
  */
 struct inode *sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd);
 void sysfs_evict_inode(struct inode *inode);
-int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr *iattr);
 int sysfs_permission(struct inode *inode, int mask);
 int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
 int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 9ad3fe5..7585d9d 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -9,6 +9,9 @@
 
 #include <linux/kernel.h>
 
+struct file;
+struct iattr;
+
 struct sysfs_dirent;
 
 #ifdef CONFIG_SYSFS
@@ -21,6 +24,7 @@ int kernfs_remove_by_name_ns(struct sysfs_dirent *parent, 
const char *name,
                             const void *ns);
 int kernfs_rename_ns(struct sysfs_dirent *sd, struct sysfs_dirent *new_parent,
                     const char *new_name, const void *new_ns);
+int kernfs_setattr(struct sysfs_dirent *sd, const struct iattr *iattr);
 
 #else  /* CONFIG_SYSFS */
 
@@ -40,6 +44,10 @@ static inline int kernfs_rename_ns(struct sysfs_dirent *sd,
                                   const char *new_name, const void *new_ns)
 { return 0; }
 
+static inline int kernfs_setattr(struct sysfs_dirent *sd,
+                                const struct iattr *iattr)
+{ return 0; }
+
 #endif /* CONFIG_SYSFS */
 
 static inline int kernfs_remove_by_name(struct sysfs_dirent *parent,
-- 
1.8.3.1

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