dd14cbc994
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>
133 lines
3.6 KiB
C
133 lines
3.6 KiB
C
struct sysfs_dirent {
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atomic_t s_count;
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struct list_head s_sibling;
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struct list_head s_children;
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void * s_element;
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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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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 spinlock_t sysfs_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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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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