diff options
| -rw-r--r-- | fs/sysfs/file.c | 109 | ||||
| -rw-r--r-- | fs/sysfs/sysfs.h | 3 |
2 files changed, 111 insertions, 1 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 3c91a57a1ed2..b13ba94cf8ac 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -49,6 +49,22 @@ static struct sysfs_ops subsys_sysfs_ops = { .store = subsys_attr_store, }; +/* + * There's one sysfs_buffer for each open file and one + * sysfs_open_dirent for each sysfs_dirent with one or more open + * files. + * + * filp->private_data points to sysfs_buffer and + * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open + * is protected by sysfs_open_dirent_lock. + */ +static spinlock_t sysfs_open_dirent_lock = SPIN_LOCK_UNLOCKED; + +struct sysfs_open_dirent { + atomic_t refcnt; + struct list_head buffers; /* goes through sysfs_buffer.list */ +}; + struct sysfs_buffer { size_t count; loff_t pos; @@ -57,6 +73,7 @@ struct sysfs_buffer { struct mutex mutex; int needs_read_fill; int event; + struct list_head list; }; /** @@ -237,6 +254,86 @@ sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t return len; } +/** + * sysfs_get_open_dirent - get or create sysfs_open_dirent + * @sd: target sysfs_dirent + * @buffer: sysfs_buffer for this instance of open + * + * If @sd->s_attr.open exists, increment its reference count; + * otherwise, create one. @buffer is chained to the buffers + * list. + * + * LOCKING: + * Kernel thread context (may sleep). + * + * RETURNS: + * 0 on success, -errno on failure. + */ +static int sysfs_get_open_dirent(struct sysfs_dirent *sd, + struct sysfs_buffer *buffer) +{ + struct sysfs_open_dirent *od, *new_od = NULL; + + retry: + spin_lock(&sysfs_open_dirent_lock); + + if (!sd->s_attr.open && new_od) { + sd->s_attr.open = new_od; + new_od = NULL; + } + + od = sd->s_attr.open; + if (od) { + atomic_inc(&od->refcnt); + list_add_tail(&buffer->list, &od->buffers); + } + + spin_unlock(&sysfs_open_dirent_lock); + + if (od) { + kfree(new_od); + return 0; + } + + /* not there, initialize a new one and retry */ + new_od = kmalloc(sizeof(*new_od), GFP_KERNEL); + if (!new_od) + return -ENOMEM; + + atomic_set(&new_od->refcnt, 0); + INIT_LIST_HEAD(&new_od->buffers); + goto retry; +} + +/** + * sysfs_put_open_dirent - put sysfs_open_dirent + * @sd: target sysfs_dirent + * @buffer: associated sysfs_buffer + * + * Put @sd->s_attr.open and unlink @buffer from the buffers list. + * If reference count reaches zero, disassociate and free it. + * + * LOCKING: + * None. + */ +static void sysfs_put_open_dirent(struct sysfs_dirent *sd, + struct sysfs_buffer *buffer) +{ + struct sysfs_open_dirent *od = sd->s_attr.open; + + spin_lock(&sysfs_open_dirent_lock); + + list_del(&buffer->list); + if (atomic_dec_and_test(&od->refcnt)) + sd->s_attr.open = NULL; + else + od = NULL; + + spin_unlock(&sysfs_open_dirent_lock); + + kfree(od); +} + static int sysfs_open_file(struct inode *inode, struct file *file) { struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata; @@ -298,19 +395,29 @@ static int sysfs_open_file(struct inode *inode, struct file *file) buffer->ops = ops; file->private_data = buffer; + /* make sure we have open dirent struct */ + error = sysfs_get_open_dirent(attr_sd, buffer); + if (error) + goto err_free; + /* open succeeded, put active references */ sysfs_put_active_two(attr_sd); return 0; + err_free: + kfree(buffer); err_out: sysfs_put_active_two(attr_sd); return error; } -static int sysfs_release(struct inode * inode, struct file * filp) +static int sysfs_release(struct inode *inode, struct file *filp) { + struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata; struct sysfs_buffer *buffer = filp->private_data; + sysfs_put_open_dirent(sd, buffer); + if (buffer->page) free_page((unsigned long)buffer->page); kfree(buffer); diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h index 42b0327d1624..3adce7d5e4f7 100644 --- a/fs/sysfs/sysfs.h +++ b/fs/sysfs/sysfs.h @@ -1,3 +1,5 @@ +struct sysfs_open_dirent; + /* type-specific structures for sysfs_dirent->s_* union members */ struct sysfs_elem_dir { struct kobject *kobj; @@ -11,6 +13,7 @@ struct sysfs_elem_symlink { struct sysfs_elem_attr { struct attribute *attr; + struct sysfs_open_dirent *open; }; struct sysfs_elem_bin_attr { |