Re: [PATCH 09/13] sysfs: Implement sysfs_getattr & sysfs_permission

[Serge E. Hallyn]

Quoting Eric W. Biederman (ebiederm@xxxxxxxxxxxx):
> From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> 
> With the implementation of sysfs_getattr and sysfs_permission
> sysfs becomes able to lazily propogate inode attribute changes
> from the sysfs_dirents to the vfs inodes.   This paves the way
> for deleting significant chunks of now unnecessary code.
>
> Acked-by: Tejun Heo <tj@xxxxxxxxxx>
> Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxx>
> ---
>  fs/sysfs/dir.c     |    2 +
>  fs/sysfs/inode.c   |   64 ++++++++++++++++++++++++++++++++++++++-------------
>  fs/sysfs/symlink.c |    3 ++
>  fs/sysfs/sysfs.h   |    2 +
>  4 files changed, 54 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
> index fa37126..25d052a 100644
> --- a/fs/sysfs/dir.c
> +++ b/fs/sysfs/dir.c
> @@ -800,7 +800,9 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
> 
>  const struct inode_operations sysfs_dir_inode_operations = {
>  	.lookup		= sysfs_lookup,
> +	.permission	= sysfs_permission,
>  	.setattr	= sysfs_setattr,
> +	.getattr	= sysfs_getattr,
>  	.setxattr	= sysfs_setxattr,
>  };
> 
> diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
> index fccfb55..2dcafe8 100644
> --- a/fs/sysfs/inode.c
> +++ b/fs/sysfs/inode.c
> @@ -37,7 +37,9 @@ static struct backing_dev_info sysfs_backing_dev_info = {
>  };
> 
>  static const struct inode_operations sysfs_inode_operations ={
> +	.permission	= sysfs_permission,
>  	.setattr	= sysfs_setattr,
> +	.getattr	= sysfs_getattr,
>  	.setxattr	= sysfs_setxattr,
>  };
> 
> @@ -196,7 +198,6 @@ static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
> 
>  static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
>  {
> -	inode->i_mode = iattr->ia_mode;
>  	inode->i_uid = iattr->ia_uid;
>  	inode->i_gid = iattr->ia_gid;
>  	inode->i_atime = iattr->ia_atime;
> @@ -227,38 +228,56 @@ static int sysfs_count_nlink(struct sysfs_dirent *sd)
>  	return nr + 2;
>  }
> 
> +static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
> +{
> +	struct sysfs_inode_attrs *iattrs = sd->s_iattr;
> +
> +	inode->i_mode = sd->s_mode;
> +	if (iattrs) {
> +		/* sysfs_dirent has non-default attributes
> +		 * get them from persistent copy in sysfs_dirent
> +		 */
> +		set_inode_attr(inode, &iattrs->ia_iattr);
> +		security_inode_notifysecctx(inode,
> +					    iattrs->ia_secdata,
> +					    iattrs->ia_secdata_len);
> +	}
> +
> +	if (sysfs_type(sd) == SYSFS_DIR)
> +		inode->i_nlink = sysfs_count_nlink(sd);
> +}
> +
> +int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
> +{
> +	struct sysfs_dirent *sd = dentry->d_fsdata;
> +	struct inode *inode = dentry->d_inode;
> +
> +	mutex_lock(&sysfs_mutex);
> +	sysfs_refresh_inode(sd, inode);
> +	mutex_unlock(&sysfs_mutex);

So the inode->i_mutex is not needed?

> +
> +	generic_fillattr(inode, stat);
> +	return 0;
> +}
> +
>  static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
>  {
>  	struct bin_attribute *bin_attr;
> -	struct sysfs_inode_attrs *iattrs;
> 
>  	inode->i_private = sysfs_get(sd);
>  	inode->i_mapping->a_ops = &sysfs_aops;
>  	inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
>  	inode->i_op = &sysfs_inode_operations;
> -	inode->i_ino = sd->s_ino;
>  	lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
> 
> -	iattrs = sd->s_iattr;
> -	if (iattrs) {
> -		/* sysfs_dirent has non-default attributes
> -		 * get them for the new inode from persistent copy
> -		 * in sysfs_dirent
> -		 */
> -		set_inode_attr(inode, &iattrs->ia_iattr);
> -		if (iattrs->ia_secdata)
> -			security_inode_notifysecctx(inode,
> -						iattrs->ia_secdata,
> -						iattrs->ia_secdata_len);
> -	} else
> -		set_default_inode_attr(inode, sd->s_mode);
> +	set_default_inode_attr(inode, sd->s_mode);
> +	sysfs_refresh_inode(sd, inode);
> 
>  	/* initialize inode according to type */
>  	switch (sysfs_type(sd)) {
>  	case SYSFS_DIR:
>  		inode->i_op = &sysfs_dir_inode_operations;
>  		inode->i_fop = &sysfs_dir_operations;
> -		inode->i_nlink = sysfs_count_nlink(sd);
>  		break;
>  	case SYSFS_KOBJ_ATTR:
>  		inode->i_size = PAGE_SIZE;
> @@ -341,3 +360,14 @@ int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
>  	else
>  		return -ENOENT;
>  }
> +
> +int sysfs_permission(struct inode *inode, int mask)
> +{
> +	struct sysfs_dirent *sd = inode->i_private;
> +
> +	mutex_lock(&sysfs_mutex);
> +	sysfs_refresh_inode(sd, inode);
> +	mutex_unlock(&sysfs_mutex);
> +
> +	return generic_permission(inode, mask, NULL);
> +}
> diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
> index 1137418..c5eff49 100644
> --- a/fs/sysfs/symlink.c
> +++ b/fs/sysfs/symlink.c
> @@ -214,6 +214,9 @@ const struct inode_operations sysfs_symlink_inode_operations = {
>  	.readlink	= generic_readlink,
>  	.follow_link	= sysfs_follow_link,
>  	.put_link	= sysfs_put_link,
> +	.setattr	= sysfs_setattr,
> +	.getattr	= sysfs_getattr,
> +	.permission	= sysfs_permission,
>  };
> 
> 
> diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
> index a96d967..12ccc07 100644
> --- a/fs/sysfs/sysfs.h
> +++ b/fs/sysfs/sysfs.h
> @@ -156,7 +156,9 @@ static inline void __sysfs_put(struct sysfs_dirent *sd)
>  struct inode *sysfs_get_inode(struct sysfs_dirent *sd);
>  void sysfs_delete_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, struct kstat *stat);
>  int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
>  		size_t size, int flags);
>  int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name);
> -- 
> 1.6.5.2.143.g8cc62
> 
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