forked from Minki/linux
8619f97989
Make sysfs_dirent->s_active an atomic_t instead of rwsem. This reduces the size of sysfs_dirent from 136 to 104 on 64bit and from 76 to 60 on 32bit with lock debugging turned off. With lock debugging turned on the reduction is much larger. s_active starts at zero and each active reference increments s_active. Putting a reference decrements s_active. Deactivation subtracts SD_DEACTIVATED_BIAS which is currently INT_MIN and assumed to be small enough to make s_active negative. If s_active is negative, sysfs_get() no longer grants new references. Deactivation succeeds immediately if there is no active user; otherwise, it waits using a completion for the last put. Due to the removal of lockdep tricks, this change makes things less trickier in release_sysfs_dirent(). As all the complexity is contained in three s_active functions, I think it's more readable this way. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
108 lines
3.2 KiB
C
108 lines
3.2 KiB
C
struct sysfs_elem_dir {
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struct kobject * kobj;
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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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};
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struct sysfs_elem_bin_attr {
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struct bin_attribute * bin_attr;
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};
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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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struct sysfs_dirent * s_parent;
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struct list_head s_sibling;
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struct list_head s_children;
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const char * s_name;
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union {
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struct sysfs_elem_dir dir;
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struct sysfs_elem_symlink symlink;
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struct sysfs_elem_attr attr;
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struct sysfs_elem_bin_attr bin_attr;
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} s_elem;
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int s_type;
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umode_t s_mode;
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ino_t s_ino;
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struct dentry * s_dentry;
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struct iattr * s_iattr;
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atomic_t s_event;
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};
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#define SD_DEACTIVATED_BIAS INT_MIN
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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 struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd);
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extern void sysfs_put_active(struct sysfs_dirent *sd);
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extern struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd);
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extern void sysfs_put_active_two(struct sysfs_dirent *sd);
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extern void sysfs_deactivate(struct sysfs_dirent *sd);
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extern void sysfs_delete_inode(struct inode *inode);
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extern void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode);
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extern struct inode * sysfs_get_inode(struct sysfs_dirent *sd);
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extern void sysfs_instantiate(struct dentry *dentry, struct inode *inode);
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extern void release_sysfs_dirent(struct sysfs_dirent * sd);
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extern int sysfs_dirent_exist(struct sysfs_dirent *, const unsigned char *);
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extern struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode,
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int type);
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extern void sysfs_attach_dirent(struct sysfs_dirent *sd,
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struct sysfs_dirent *parent_sd,
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struct dentry *dentry);
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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 void sysfs_drop_dentry(struct sysfs_dirent *sd);
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extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
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extern spinlock_t sysfs_lock;
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extern spinlock_t kobj_sysfs_assoc_lock;
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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 const struct inode_operations sysfs_dir_inode_operations;
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extern const struct inode_operations sysfs_symlink_inode_operations;
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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 (sd && 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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