![Eric W. Biederman](/assets/img/avatar_default.png)
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/*, /sys/devices/virtual/net/*, and potentially a few other directories of the form /sys/ ... /net/*. What this patch does is to add an additional tag field to the sysfs dirent structure. For directories that should show different contents depending on the context such as /sys/class/net/, and /sys/devices/virtual/net/ this tag field is used to specify the context in which those directories should be visible. Effectively this is the same as creating multiple distinct directories with the same name but internally to sysfs the result is nicer. I am calling the concept of a single directory that looks like multiple directories all at the same path in the filesystem tagged directories. For the networking namespace the set of directories whose contents I need to filter with tags can depend on the presence or absence of hotplug hardware or which modules are currently loaded. Which means I need a simple race free way to setup those directories as tagged. To achieve a reace free design all tagged directories are created and managed by sysfs itself. Users of this interface: - define a type in the sysfs_tag_type enumeration. - call sysfs_register_ns_types with the type and it's operations - sysfs_exit_ns when an individual tag is no longer valid - Implement mount_ns() which returns the ns of the calling process so we can attach it to a sysfs superblock. - Implement ktype.namespace() which returns the ns of a syfs kobject. Everything else is left up to sysfs and the driver layer. For the network namespace mount_ns and namespace() are essentially one line functions, and look to remain that. Tags are currently represented a const void * pointers as that is both generic, prevides enough information for equality comparisons, and is trivial to create for current users, as it is just the existing namespace pointer. The work needed in sysfs is more extensive. At each directory or symlink creating I need to check if the directory it is being created in is a tagged directory and if so generate the appropriate tag to place on the sysfs_dirent. Likewise at each symlink or directory removal I need to check if the sysfs directory it is being removed from is a tagged directory and if so figure out which tag goes along with the name I am deleting. Currently only directories which hold kobjects, and symlinks are supported. There is not enough information in the current file attribute interfaces to give us anything to discriminate on which makes it useless, and there are no potential users which makes it an uninteresting problem to solve. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Benjamin Thery <benjamin.thery@bull.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
220 lines
6 KiB
C
220 lines
6 KiB
C
/*
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* fs/sysfs/sysfs.h - sysfs internal header file
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*/
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#include <linux/lockdep.h>
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#include <linux/fs.h>
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struct sysfs_open_dirent;
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/* type-specific structures for sysfs_dirent->s_* union members */
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struct sysfs_elem_dir {
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struct kobject *kobj;
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/* children list starts here and goes through sd->s_sibling */
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struct sysfs_dirent *children;
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};
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struct sysfs_elem_symlink {
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struct sysfs_dirent *target_sd;
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};
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struct sysfs_elem_attr {
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struct attribute *attr;
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struct sysfs_open_dirent *open;
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};
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struct sysfs_elem_bin_attr {
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struct bin_attribute *bin_attr;
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struct hlist_head buffers;
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};
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struct sysfs_inode_attrs {
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struct iattr ia_iattr;
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void *ia_secdata;
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u32 ia_secdata_len;
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};
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/*
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* sysfs_dirent - the building block of sysfs hierarchy. Each and
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* every sysfs node is represented by single sysfs_dirent.
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*
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* As long as s_count reference is held, the sysfs_dirent itself is
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* accessible. Dereferencing s_elem or any other outer entity
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* requires s_active reference.
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*/
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struct sysfs_dirent {
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atomic_t s_count;
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atomic_t s_active;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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struct sysfs_dirent *s_parent;
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struct sysfs_dirent *s_sibling;
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const char *s_name;
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const void *s_ns;
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union {
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struct sysfs_elem_dir s_dir;
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struct sysfs_elem_symlink s_symlink;
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struct sysfs_elem_attr s_attr;
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struct sysfs_elem_bin_attr s_bin_attr;
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};
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unsigned int s_flags;
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unsigned short s_mode;
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ino_t s_ino;
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struct sysfs_inode_attrs *s_iattr;
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};
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#define SD_DEACTIVATED_BIAS INT_MIN
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#define SYSFS_TYPE_MASK 0x00ff
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#define SYSFS_DIR 0x0001
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#define SYSFS_KOBJ_ATTR 0x0002
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#define SYSFS_KOBJ_BIN_ATTR 0x0004
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#define SYSFS_KOBJ_LINK 0x0008
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#define SYSFS_COPY_NAME (SYSFS_DIR | SYSFS_KOBJ_LINK)
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#define SYSFS_ACTIVE_REF (SYSFS_KOBJ_ATTR | SYSFS_KOBJ_BIN_ATTR)
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#define SYSFS_NS_TYPE_MASK 0xff00
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#define SYSFS_NS_TYPE_SHIFT 8
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#define SYSFS_FLAG_MASK ~(SYSFS_NS_TYPE_MASK|SYSFS_TYPE_MASK)
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#define SYSFS_FLAG_REMOVED 0x020000
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static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
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{
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return sd->s_flags & SYSFS_TYPE_MASK;
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}
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static inline enum kobj_ns_type sysfs_ns_type(struct sysfs_dirent *sd)
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{
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return (sd->s_flags & SYSFS_NS_TYPE_MASK) >> SYSFS_NS_TYPE_SHIFT;
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}
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#define sysfs_dirent_init_lockdep(sd) \
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do { \
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struct attribute *attr = sd->s_attr.attr; \
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struct lock_class_key *key = attr->key; \
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if (!key) \
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key = &attr->skey; \
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\
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lockdep_init_map(&sd->dep_map, "s_active", key, 0); \
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} while(0)
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#else
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#define sysfs_dirent_init_lockdep(sd) do {} while(0)
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#endif
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/*
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* Context structure to be used while adding/removing nodes.
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*/
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struct sysfs_addrm_cxt {
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struct sysfs_dirent *parent_sd;
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struct sysfs_dirent *removed;
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};
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/*
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* mount.c
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*/
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struct sysfs_super_info {
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const void *ns[KOBJ_NS_TYPES];
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};
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#define sysfs_info(SB) ((struct sysfs_super_info *)(SB->s_fs_info))
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extern struct sysfs_dirent sysfs_root;
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extern struct kmem_cache *sysfs_dir_cachep;
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/*
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* dir.c
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*/
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extern struct mutex sysfs_mutex;
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extern spinlock_t sysfs_assoc_lock;
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extern const struct file_operations sysfs_dir_operations;
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extern const struct inode_operations sysfs_dir_inode_operations;
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struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd);
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struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd);
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void sysfs_put_active(struct sysfs_dirent *sd);
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void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
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struct sysfs_dirent *parent_sd);
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int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd);
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int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd);
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void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd);
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void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt);
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struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
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const void *ns,
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const unsigned char *name);
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struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
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const void *ns,
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const unsigned char *name);
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struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type);
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void release_sysfs_dirent(struct sysfs_dirent *sd);
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int sysfs_create_subdir(struct kobject *kobj, const char *name,
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struct sysfs_dirent **p_sd);
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void sysfs_remove_subdir(struct sysfs_dirent *sd);
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int sysfs_rename(struct sysfs_dirent *sd,
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struct sysfs_dirent *new_parent_sd, const void *ns, const char *new_name);
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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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#define sysfs_get(sd) __sysfs_get(sd)
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static inline void __sysfs_put(struct sysfs_dirent *sd)
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{
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if (sd && atomic_dec_and_test(&sd->s_count))
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release_sysfs_dirent(sd);
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}
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#define sysfs_put(sd) __sysfs_put(sd)
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/*
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* inode.c
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*/
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struct inode *sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd);
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void sysfs_delete_inode(struct inode *inode);
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int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr *iattr);
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int sysfs_permission(struct inode *inode, int mask);
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int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
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int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat);
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int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
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size_t size, int flags);
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int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const char *name);
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int sysfs_inode_init(void);
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/*
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* file.c
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*/
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extern const struct file_operations sysfs_file_operations;
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int sysfs_add_file(struct sysfs_dirent *dir_sd,
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const struct attribute *attr, int type);
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int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
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const struct attribute *attr, int type, mode_t amode);
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/*
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* bin.c
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*/
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extern const struct file_operations bin_fops;
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void unmap_bin_file(struct sysfs_dirent *attr_sd);
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/*
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* symlink.c
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*/
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extern const struct inode_operations sysfs_symlink_inode_operations;
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