linux/fs/sysfs/sysfs.h
Tejun Heo dd14cbc994 sysfs: fix race condition around sd->s_dentry, take#2
Allowing attribute and symlink dentries to be reclaimed means
sd->s_dentry can change dynamically.  However, updates to the field
are unsynchronized leading to race conditions.  This patch adds
sysfs_lock and use it to synchronize updates to sd->s_dentry.

Due to the locking around ->d_iput, the check in sysfs_drop_dentry()
is complex.  sysfs_lock only protect sd->s_dentry pointer itself.  The
validity of the dentry is protected by dcache_lock, so whether dentry
is alive or not can only be tested while holding both locks.

This is minimal backport of sysfs_drop_dentry() rewrite in devel
branch.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2007-06-12 16:08:47 -07:00

132 lines
3.6 KiB
C

struct sysfs_dirent {
atomic_t s_count;
struct list_head s_sibling;
struct list_head s_children;
void * s_element;
int s_type;
umode_t s_mode;
ino_t s_ino;
struct dentry * s_dentry;
struct iattr * s_iattr;
atomic_t s_event;
};
extern struct vfsmount * sysfs_mount;
extern struct kmem_cache *sysfs_dir_cachep;
extern void sysfs_delete_inode(struct inode *inode);
extern struct inode * sysfs_new_inode(mode_t mode, struct sysfs_dirent *);
extern int sysfs_create(struct dentry *, int mode, int (*init)(struct inode *));
extern int sysfs_dirent_exist(struct sysfs_dirent *, const unsigned char *);
extern int sysfs_make_dirent(struct sysfs_dirent *, struct dentry *, void *,
umode_t, int);
extern int sysfs_add_file(struct dentry *, const struct attribute *, int);
extern int sysfs_hash_and_remove(struct dentry * dir, const char * name);
extern struct sysfs_dirent *sysfs_find(struct sysfs_dirent *dir, const char * name);
extern int sysfs_create_subdir(struct kobject *, const char *, struct dentry **);
extern void sysfs_remove_subdir(struct dentry *);
extern const unsigned char * sysfs_get_name(struct sysfs_dirent *sd);
extern void sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent);
extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
extern spinlock_t sysfs_lock;
extern struct rw_semaphore sysfs_rename_sem;
extern struct super_block * sysfs_sb;
extern const struct file_operations sysfs_dir_operations;
extern const struct file_operations sysfs_file_operations;
extern const struct file_operations bin_fops;
extern const struct inode_operations sysfs_dir_inode_operations;
extern const struct inode_operations sysfs_symlink_inode_operations;
struct sysfs_symlink {
char * link_name;
struct kobject * target_kobj;
};
struct sysfs_buffer {
struct list_head associates;
size_t count;
loff_t pos;
char * page;
struct sysfs_ops * ops;
struct semaphore sem;
int orphaned;
int needs_read_fill;
int event;
};
struct sysfs_buffer_collection {
struct list_head associates;
};
static inline struct kobject * to_kobj(struct dentry * dentry)
{
struct sysfs_dirent * sd = dentry->d_fsdata;
return ((struct kobject *) sd->s_element);
}
static inline struct attribute * to_attr(struct dentry * dentry)
{
struct sysfs_dirent * sd = dentry->d_fsdata;
return ((struct attribute *) sd->s_element);
}
static inline struct bin_attribute * to_bin_attr(struct dentry * dentry)
{
struct sysfs_dirent * sd = dentry->d_fsdata;
return ((struct bin_attribute *) sd->s_element);
}
static inline struct kobject *sysfs_get_kobject(struct dentry *dentry)
{
struct kobject * kobj = NULL;
spin_lock(&dcache_lock);
if (!d_unhashed(dentry)) {
struct sysfs_dirent * sd = dentry->d_fsdata;
if (sd->s_type & SYSFS_KOBJ_LINK) {
struct sysfs_symlink * sl = sd->s_element;
kobj = kobject_get(sl->target_kobj);
} else
kobj = kobject_get(sd->s_element);
}
spin_unlock(&dcache_lock);
return kobj;
}
static inline void release_sysfs_dirent(struct sysfs_dirent * sd)
{
if (sd->s_type & SYSFS_KOBJ_LINK) {
struct sysfs_symlink * sl = sd->s_element;
kfree(sl->link_name);
kobject_put(sl->target_kobj);
kfree(sl);
}
kfree(sd->s_iattr);
kmem_cache_free(sysfs_dir_cachep, sd);
}
static inline struct sysfs_dirent * sysfs_get(struct sysfs_dirent * sd)
{
if (sd) {
WARN_ON(!atomic_read(&sd->s_count));
atomic_inc(&sd->s_count);
}
return sd;
}
static inline void sysfs_put(struct sysfs_dirent * sd)
{
if (atomic_dec_and_test(&sd->s_count))
release_sysfs_dirent(sd);
}
static inline int sysfs_is_shadowed_inode(struct inode *inode)
{
return S_ISDIR(inode->i_mode) && inode->i_op->follow_link;
}