0cae60f914
sysfs_assoc_lock is an odd piece of locking. In general, whoever owns a kobject is responsible for synchronizing sysfs operations and sysfs proper assumes that, for example, removal won't race with any other operation; however, this doesn't work for symlinking because an entity performing symlink doesn't usually own the target kobject and thus has no control over its removal. sysfs_assoc_lock synchronizes symlink operations against kobj->sd disassociation so that symlink code doesn't end up dereferencing already freed sysfs_dirent by racing with removal of the target kobject. This is quite obscure and the generic name of the lock and lack of comments make it difficult to understand its role. Let's rename it to sysfs_symlink_target_lock and add comments explaining what's going on. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
245 lines
6.5 KiB
C
245 lines
6.5 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/kobject_ns.h>
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#include <linux/fs.h>
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#include <linux/rbtree.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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unsigned long subdirs;
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/* children rbtree starts here and goes through sd->s_rb */
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struct rb_root 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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union {
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struct attribute *attr;
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struct bin_attribute *bin_attr;
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};
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struct sysfs_open_dirent *open;
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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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const char *s_name;
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struct rb_node s_rb;
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union {
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struct completion *completion;
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struct sysfs_dirent *removed_list;
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} u;
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const void *s_ns; /* namespace tag */
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unsigned int s_hash; /* ns + name hash */
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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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};
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unsigned short s_flags;
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umode_t s_mode;
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unsigned int 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_FLAG_MASK ~SYSFS_TYPE_MASK
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#define SYSFS_FLAG_HAS_NS 0x01000
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#define SYSFS_FLAG_REMOVED 0x02000
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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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#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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/* Test for attributes that want to ignore lockdep for read-locking */
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static inline bool sysfs_ignore_lockdep(struct sysfs_dirent *sd)
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{
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int type = sysfs_type(sd);
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return (type == SYSFS_KOBJ_ATTR || type == SYSFS_KOBJ_BIN_ATTR) &&
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sd->s_attr.attr->ignore_lockdep;
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}
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#else
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#define sysfs_dirent_init_lockdep(sd) do {} while (0)
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static inline bool sysfs_ignore_lockdep(struct sysfs_dirent *sd)
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{
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return true;
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}
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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 *removed;
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};
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/*
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* mount.c
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*/
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/*
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* Each sb is associated with one namespace tag, currently the network
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* namespace of the task which mounted this sysfs instance. If multiple
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* tags become necessary, make the following an array and compare
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* sysfs_dirent tag against every entry.
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*/
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struct sysfs_super_info {
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void *ns;
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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_symlink_target_lock;
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extern const struct dentry_operations sysfs_dentry_ops;
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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 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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void sysfs_warn_dup(struct sysfs_dirent *parent, const char *name);
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int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd,
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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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struct sysfs_dirent *parent_sd);
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void sysfs_remove(struct sysfs_dirent *sd);
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int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name,
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const void *ns);
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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 unsigned char *name,
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const void *ns);
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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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int sysfs_rename(struct sysfs_dirent *sd, struct sysfs_dirent *new_parent_sd,
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const char *new_name, const void *new_ns);
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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_evict_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,
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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_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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extern const struct file_operations sysfs_bin_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_ns(struct sysfs_dirent *dir_sd,
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const struct attribute *attr, int type,
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umode_t amode, const void *ns);
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void sysfs_unmap_bin_file(struct sysfs_dirent *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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int sysfs_create_link_sd(struct sysfs_dirent *sd, struct kobject *target,
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const char *name);
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