[PATCH] sysfs-iattr: add sysfs_setattr

o This adds ->i_op->setattr VFS method for sysfs inodes. The changed
  attribues are saved in the persistent sysfs_dirent structure as a pointer
  to struct iattr. The struct iattr is allocated only for those sysfs_dirent's
  for which default attributes are getting changed. Thanks to Jon Smirl for
  this suggestion.

Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 68 insertions, 0 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 5cf3270014c..37d7a6875d8 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -233,6 +233,7 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
 
 struct inode_operations sysfs_dir_inode_operations = {
         .lookup         = sysfs_lookup,
+        .setattr        = sysfs_setattr,
 };
 
 static void remove_dir(struct dentry * d)
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index aff7b2dfa8e..400c90be568 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -26,6 +26,71 @@ static struct backing_dev_info sysfs_backing_dev_info = {
         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
 };
 
+static struct inode_operations sysfs_inode_operations ={
+        .setattr        = sysfs_setattr,
+};
+
+int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
+{
+        struct inode * inode = dentry->d_inode;
+        struct sysfs_dirent * sd = dentry->d_fsdata;
+        struct iattr * sd_iattr;
+        unsigned int ia_valid = iattr->ia_valid;
+        int error;
+
+        if (!sd)
+                return -EINVAL;
+
+        sd_iattr = sd->s_iattr;
+
+        error = inode_change_ok(inode, iattr);
+        if (error)
+                return error;
+
+        error = inode_setattr(inode, iattr);
+        if (error)
+                return error;
+
+        if (!sd_iattr) {
+                /* setting attributes for the first time, allocate now */
+                sd_iattr = kmalloc(sizeof(struct iattr), GFP_KERNEL);
+                if (!sd_iattr)
+                        return -ENOMEM;
+                /* assign default attributes */
+                memset(sd_iattr, 0, sizeof(struct iattr));
+                sd_iattr->ia_mode = sd->s_mode;
+                sd_iattr->ia_uid = 0;
+                sd_iattr->ia_gid = 0;
+                sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
+                sd->s_iattr = sd_iattr;
+        }
+
+        /* attributes were changed atleast once in past */
+
+        if (ia_valid & ATTR_UID)
+                sd_iattr->ia_uid = iattr->ia_uid;
+        if (ia_valid & ATTR_GID)
+                sd_iattr->ia_gid = iattr->ia_gid;
+        if (ia_valid & ATTR_ATIME)
+                sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
+                                                inode->i_sb->s_time_gran);
+        if (ia_valid & ATTR_MTIME)
+                sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
+                                                inode->i_sb->s_time_gran);
+        if (ia_valid & ATTR_CTIME)
+                sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
+                                                inode->i_sb->s_time_gran);
+        if (ia_valid & ATTR_MODE) {
+                umode_t mode = iattr->ia_mode;
+
+                if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
+                        mode &= ~S_ISGID;
+                sd_iattr->ia_mode = mode;
+        }
+
+        return error;
+}
+
 struct inode * sysfs_new_inode(mode_t mode)
 {
         struct inode * inode = new_inode(sysfs_sb);
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index a8a24a0c0b3..e8e9f0c2573 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -17,6 +17,7 @@ extern void sysfs_remove_subdir(struct dentry *);
 
 extern const unsigned char * sysfs_get_name(struct sysfs_dirent *sd);
 extern void sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent);
+extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
 
 extern struct rw_semaphore sysfs_rename_sem;
 extern struct super_block * sysfs_sb;
@@ -75,6 +76,7 @@ static inline void release_sysfs_dirent(struct sysfs_dirent * sd)
                 kobject_put(sl->target_kobj);
                 kfree(sl);
         }
+        kfree(sd->s_iattr);
         kmem_cache_free(sysfs_dir_cachep, sd);
 }