b592fcfe7f
The problem. When implementing a network namespace I need to be able to have multiple network devices with the same name. Currently this is a problem for /sys/class/net/*. What I want is a separate /sys/class/net directory in sysfs for each network namespace, and I want to name each of them /sys/class/net. I looked and the VFS actually allows that. All that is needed is for /sys/class/net to implement a follow link method to redirect lookups to the real directory you want. Implementing a follow link method that is sensitive to the current network namespace turns out to be 3 lines of code so it looks like a clean approach. Modifying sysfs so it doesn't get in my was is a bit trickier. I am calling the concept of multiple directories all at the same path in the filesystem shadow directories. With the directory entry really at that location the shadow master. The following patch modifies sysfs so it can handle a directory structure slightly different from the kobject tree so I can implement the shadow directories for handling /sys/class/net/. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Maneesh Soni <maneesh@in.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
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extern struct vfsmount * sysfs_mount;
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extern struct kmem_cache *sysfs_dir_cachep;
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extern void sysfs_delete_inode(struct inode *inode);
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extern struct inode * sysfs_new_inode(mode_t mode, struct sysfs_dirent *);
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extern int sysfs_create(struct dentry *, int mode, int (*init)(struct inode *));
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extern int sysfs_dirent_exist(struct sysfs_dirent *, const unsigned char *);
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extern int sysfs_make_dirent(struct sysfs_dirent *, struct dentry *, void *,
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umode_t, int);
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extern int sysfs_add_file(struct dentry *, const struct attribute *, int);
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extern int sysfs_hash_and_remove(struct dentry * dir, const char * name);
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extern struct sysfs_dirent *sysfs_find(struct sysfs_dirent *dir, const char * name);
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extern int sysfs_create_subdir(struct kobject *, const char *, struct dentry **);
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extern void sysfs_remove_subdir(struct dentry *);
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extern const unsigned char * sysfs_get_name(struct sysfs_dirent *sd);
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extern void sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent);
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extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
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extern struct rw_semaphore sysfs_rename_sem;
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extern struct super_block * sysfs_sb;
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extern const struct file_operations sysfs_dir_operations;
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extern const struct file_operations sysfs_file_operations;
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extern const struct file_operations bin_fops;
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extern struct inode_operations sysfs_dir_inode_operations;
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extern struct inode_operations sysfs_symlink_inode_operations;
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struct sysfs_symlink {
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char * link_name;
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struct kobject * target_kobj;
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};
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struct sysfs_buffer {
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struct list_head associates;
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size_t count;
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loff_t pos;
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char * page;
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struct sysfs_ops * ops;
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struct semaphore sem;
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int orphaned;
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int needs_read_fill;
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int event;
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};
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struct sysfs_buffer_collection {
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struct list_head associates;
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};
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static inline struct kobject * to_kobj(struct dentry * dentry)
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{
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struct sysfs_dirent * sd = dentry->d_fsdata;
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return ((struct kobject *) sd->s_element);
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}
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static inline struct attribute * to_attr(struct dentry * dentry)
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{
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struct sysfs_dirent * sd = dentry->d_fsdata;
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return ((struct attribute *) sd->s_element);
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}
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static inline struct bin_attribute * to_bin_attr(struct dentry * dentry)
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{
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struct sysfs_dirent * sd = dentry->d_fsdata;
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return ((struct bin_attribute *) sd->s_element);
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}
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static inline struct kobject *sysfs_get_kobject(struct dentry *dentry)
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{
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struct kobject * kobj = NULL;
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spin_lock(&dcache_lock);
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if (!d_unhashed(dentry)) {
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struct sysfs_dirent * sd = dentry->d_fsdata;
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if (sd->s_type & SYSFS_KOBJ_LINK) {
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struct sysfs_symlink * sl = sd->s_element;
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kobj = kobject_get(sl->target_kobj);
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} else
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kobj = kobject_get(sd->s_element);
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}
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spin_unlock(&dcache_lock);
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return kobj;
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}
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static inline void release_sysfs_dirent(struct sysfs_dirent * sd)
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{
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if (sd->s_type & SYSFS_KOBJ_LINK) {
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struct sysfs_symlink * sl = sd->s_element;
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kfree(sl->link_name);
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kobject_put(sl->target_kobj);
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kfree(sl);
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}
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kfree(sd->s_iattr);
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kmem_cache_free(sysfs_dir_cachep, sd);
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}
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static inline struct sysfs_dirent * sysfs_get(struct sysfs_dirent * sd)
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{
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if (sd) {
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WARN_ON(!atomic_read(&sd->s_count));
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atomic_inc(&sd->s_count);
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}
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return sd;
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}
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static inline void sysfs_put(struct sysfs_dirent * sd)
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{
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if (atomic_dec_and_test(&sd->s_count))
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release_sysfs_dirent(sd);
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}
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static inline int sysfs_is_shadowed_inode(struct inode *inode)
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{
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return S_ISDIR(inode->i_mode) && inode->i_op->follow_link;
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}
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