base.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 2,003 行 · 第 1/5 页

struct devfsd_buf_entry {
	struct devfs_entry *de;	/*  The name is generated with this         */
	unsigned short type;	/*  The type of event                       */
	umode_t mode;
	uid_t uid;
	gid_t gid;
	struct devfsd_buf_entry *next;
};

struct fs_info {		/*  This structure is for the mounted devfs  */
	struct super_block *sb;
	spinlock_t devfsd_buffer_lock;	/*  Lock when inserting/deleting events  */
	struct devfsd_buf_entry *devfsd_first_event;
	struct devfsd_buf_entry *devfsd_last_event;
	volatile int devfsd_sleeping;
	volatile struct task_struct *devfsd_task;
	volatile pid_t devfsd_pgrp;
	volatile struct file *devfsd_file;
	struct devfsd_notify_struct *devfsd_info;
	volatile unsigned long devfsd_event_mask;
	atomic_t devfsd_overrun_count;
	wait_queue_head_t devfsd_wait_queue;	/*  Wake devfsd on input       */
	wait_queue_head_t revalidate_wait_queue;	/*  Wake when devfsd sleeps    */
};

static struct fs_info fs_info = {.devfsd_buffer_lock = SPIN_LOCK_UNLOCKED };
static kmem_cache_t *devfsd_buf_cache;
#ifdef CONFIG_DEVFS_DEBUG
static unsigned int devfs_debug_init __initdata = DEBUG_NONE;
static unsigned int devfs_debug = DEBUG_NONE;
static spinlock_t stat_lock = SPIN_LOCK_UNLOCKED;
static unsigned int stat_num_entries;
static unsigned int stat_num_bytes;
#endif
static unsigned char poison_array[8] =
    { 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a };

#ifdef CONFIG_DEVFS_MOUNT
static unsigned int boot_options = OPTION_MOUNT;
#else
static unsigned int boot_options = OPTION_NONE;
#endif

/*  Forward function declarations  */
static devfs_handle_t _devfs_walk_path(struct devfs_entry *dir,
				       const char *name, int namelen,
				       int traverse_symlink);
static ssize_t devfsd_read(struct file *file, char __user *buf, size_t len,
			   loff_t * ppos);
static int devfsd_ioctl(struct inode *inode, struct file *file,
			unsigned int cmd, unsigned long arg);
static int devfsd_close(struct inode *inode, struct file *file);
#ifdef CONFIG_DEVFS_DEBUG
static ssize_t stat_read(struct file *file, char __user *buf, size_t len,
			 loff_t * ppos);
static struct file_operations stat_fops = {
	.open = nonseekable_open,
	.read = stat_read,
};
#endif

/*  Devfs daemon file operations  */
static struct file_operations devfsd_fops = {
	.open = nonseekable_open,
	.read = devfsd_read,
	.ioctl = devfsd_ioctl,
	.release = devfsd_close,
};

/*  Support functions follow  */

/**
 *	devfs_get - Get a reference to a devfs entry.
 *	@de:  The devfs entry.
 */

static struct devfs_entry *devfs_get(struct devfs_entry *de)
{
	VERIFY_ENTRY(de);
	if (de)
		atomic_inc(&de->refcount);
	return de;
}				/*  End Function devfs_get  */

/**
 *	devfs_put - Put (release) a reference to a devfs entry.
 *	@de:  The handle to the devfs entry.
 */

static void devfs_put(devfs_handle_t de)
{
	if (!de)
		return;
	VERIFY_ENTRY(de);
	if (de->info == POISON_PTR)
		OOPS("(%p): poisoned pointer\n", de);
	if (!atomic_dec_and_test(&de->refcount))
		return;
	if (de == root_entry)
		OOPS("(%p): root entry being freed\n", de);
	DPRINTK(DEBUG_FREE, "(%s): de: %p, parent: %p \"%s\"\n",
		de->name, de, de->parent,
		de->parent ? de->parent->name : "no parent");
	if (S_ISLNK(de->mode))
		kfree(de->u.symlink.linkname);
	WRITE_ENTRY_MAGIC(de, 0);
#ifdef CONFIG_DEVFS_DEBUG
	spin_lock(&stat_lock);
	--stat_num_entries;
	stat_num_bytes -= sizeof *de + de->namelen;
	if (S_ISLNK(de->mode))
		stat_num_bytes -= de->u.symlink.length + 1;
	spin_unlock(&stat_lock);
#endif
	de->info = POISON_PTR;
	kfree(de);
}				/*  End Function devfs_put  */

/**
 *	_devfs_search_dir - Search for a devfs entry in a directory.
 *	@dir:  The directory to search.
 *	@name:  The name of the entry to search for.
 *	@namelen:  The number of characters in @name.
 *
 *  Search for a devfs entry in a directory and returns a pointer to the entry
 *   on success, else %NULL. The directory must be locked already.
 *   An implicit devfs_get() is performed on the returned entry.
 */

static struct devfs_entry *_devfs_search_dir(struct devfs_entry *dir,
					     const char *name,
					     unsigned int namelen)
{
	struct devfs_entry *curr;

	if (!S_ISDIR(dir->mode)) {
		PRINTK("(%s): not a directory\n", dir->name);
		return NULL;
	}
	for (curr = dir->u.dir.first; curr != NULL; curr = curr->next) {
		if (curr->namelen != namelen)
			continue;
		if (memcmp(curr->name, name, namelen) == 0)
			break;
		/*  Not found: try the next one  */
	}
	return devfs_get(curr);
}				/*  End Function _devfs_search_dir  */

/**
 *	_devfs_alloc_entry - Allocate a devfs entry.
 *	@name:     the name of the entry
 *	@namelen:  the number of characters in @name
 *      @mode:     the mode for the entry
 *
 *  Allocate a devfs entry and returns a pointer to the entry on success, else
 *   %NULL.
 */

static struct devfs_entry *_devfs_alloc_entry(const char *name,
					      unsigned int namelen,
					      umode_t mode)
{
	struct devfs_entry *new;
	static unsigned long inode_counter = FIRST_INODE;
	static spinlock_t counter_lock = SPIN_LOCK_UNLOCKED;

	if (name && (namelen < 1))
		namelen = strlen(name);
	if ((new = kmalloc(sizeof *new + namelen, GFP_KERNEL)) == NULL)
		return NULL;
	memset(new, 0, sizeof *new + namelen);	/*  Will set '\0' on name  */
	new->mode = mode;
	if (S_ISDIR(mode))
		rwlock_init(&new->u.dir.lock);
	atomic_set(&new->refcount, 1);
	spin_lock(&counter_lock);
	new->inode.ino = inode_counter++;
	spin_unlock(&counter_lock);
	if (name)
		memcpy(new->name, name, namelen);
	new->namelen = namelen;
	WRITE_ENTRY_MAGIC(new, MAGIC_VALUE);
#ifdef CONFIG_DEVFS_DEBUG
	spin_lock(&stat_lock);
	++stat_num_entries;
	stat_num_bytes += sizeof *new + namelen;
	spin_unlock(&stat_lock);
#endif
	return new;
}				/*  End Function _devfs_alloc_entry  */

/**
 *	_devfs_append_entry - Append a devfs entry to a directory's child list.
 *	@dir:  The directory to add to.
 *	@de:  The devfs entry to append.
 *	@old_de: If an existing entry exists, it will be written here. This may
 *		 be %NULL. An implicit devfs_get() is performed on this entry.
 *
 *  Append a devfs entry to a directory's list of children, checking first to
 *   see if an entry of the same name exists. The directory will be locked.
 *   The value 0 is returned on success, else a negative error code.
 *   On failure, an implicit devfs_put() is performed on %de.
 */

static int _devfs_append_entry(devfs_handle_t dir, devfs_handle_t de,
			       devfs_handle_t * old_de)
{
	int retval;

	if (old_de)
		*old_de = NULL;
	if (!S_ISDIR(dir->mode)) {
		PRINTK("(%s): dir: \"%s\" is not a directory\n", de->name,
		       dir->name);
		devfs_put(de);
		return -ENOTDIR;
	}
	write_lock(&dir->u.dir.lock);
	if (dir->u.dir.no_more_additions)
		retval = -ENOENT;
	else {
		struct devfs_entry *old;

		old = _devfs_search_dir(dir, de->name, de->namelen);
		if (old_de)
			*old_de = old;
		else
			devfs_put(old);
		if (old == NULL) {
			de->parent = dir;
			de->prev = dir->u.dir.last;
			/*  Append to the directory's list of children  */
			if (dir->u.dir.first == NULL)
				dir->u.dir.first = de;
			else
				dir->u.dir.last->next = de;
			dir->u.dir.last = de;
			retval = 0;
		} else
			retval = -EEXIST;
	}
	write_unlock(&dir->u.dir.lock);
	if (retval)
		devfs_put(de);
	return retval;
}				/*  End Function _devfs_append_entry  */

/**
 *	_devfs_get_root_entry - Get the root devfs entry.
 *
 *	Returns the root devfs entry on success, else %NULL.
 *
 *	TODO it must be called asynchronously due to the fact
 *	that devfs is initialized relatively late. Proper way
 *	is to remove module_init from init_devfs_fs and manually
 *	call it early enough during system init
 */

static struct devfs_entry *_devfs_get_root_entry(void)
{
	struct devfs_entry *new;
	static spinlock_t root_lock = SPIN_LOCK_UNLOCKED;

	if (root_entry)
		return root_entry;

	new = _devfs_alloc_entry(NULL, 0, MODE_DIR);
	if (new == NULL)
		return NULL;

	spin_lock(&root_lock);
	if (root_entry) {
		spin_unlock(&root_lock);
		devfs_put(new);
		return root_entry;
	}
	root_entry = new;
	spin_unlock(&root_lock);

	return root_entry;
}				/*  End Function _devfs_get_root_entry  */

/**
 *	_devfs_descend - Descend down a tree using the next component name.
 *	@dir:  The directory to search.
 *	@name:  The component name to search for.
 *	@namelen:  The length of %name.
 *	@next_pos:  The position of the next '/' or '\0' is written here.
 *
 *  Descend into a directory, searching for a component. This function forms
 *   the core of a tree-walking algorithm. The directory will be locked.
 *   The devfs entry corresponding to the component is returned. If there is
 *   no matching entry, %NULL is returned.
 *   An implicit devfs_get() is performed on the returned entry.
 */

static struct devfs_entry *_devfs_descend(struct devfs_entry *dir,
					  const char *name, int namelen,
					  int *next_pos)
{
	const char *stop, *ptr;
	struct devfs_entry *entry;

	if ((namelen >= 3) && (strncmp(name, "../", 3) == 0)) {	/*  Special-case going to parent directory  */
		*next_pos = 3;
		return devfs_get(dir->parent);
	}
	stop = name + namelen;
	/*  Search for a possible '/'  */
	for (ptr = name; (ptr < stop) && (*ptr != '/'); ++ptr) ;
	*next_pos = ptr - name;
	read_lock(&dir->u.dir.lock);
	entry = _devfs_search_dir(dir, name, *next_pos);
	read_unlock(&dir->u.dir.lock);
	return entry;
}				/*  End Function _devfs_descend  */

static devfs_handle_t _devfs_make_parent_for_leaf(struct devfs_entry *dir,
						  const char *name,
						  int namelen, int *leaf_pos)
{
	int next_pos = 0;

	if (dir == NULL)
		dir = _devfs_get_root_entry();
	if (dir == NULL)
		return NULL;
	devfs_get(dir);
	/*  Search for possible trailing component and ignore it  */
	for (--namelen; (namelen > 0) && (name[namelen] != '/'); --namelen) ;
	*leaf_pos = (name[namelen] == '/') ? (namelen + 1) : 0;
	for (; namelen > 0; name += next_pos, namelen -= next_pos) {
		struct devfs_entry *de, *old = NULL;

		if ((de =
		     _devfs_descend(dir, name, namelen, &next_pos)) == NULL) {
			de = _devfs_alloc_entry(name, next_pos, MODE_DIR);
			devfs_get(de);
			if (!de || _devfs_append_entry(dir, de, &old)) {
				devfs_put(de);
				if (!old || !S_ISDIR(old->mode)) {
					devfs_put(old);
					devfs_put(dir);
					return NULL;
				}
				de = old;	/*  Use the existing directory  */
			}
		}
		if (de == dir->parent) {
			devfs_put(dir);
			devfs_put(de);
			return NULL;
		}
		devfs_put(dir);
		dir = de;
		if (name[next_pos] == '/')
			++next_pos;
	}
	return dir;
}				/*  End Function _devfs_make_parent_for_leaf  */

static devfs_handle_t _devfs_prepare_leaf(devfs_handle_t * dir,
					  const char *name, umode_t mode)
{
	int namelen, leaf_pos;
	struct devfs_entry *de;

	namelen = strlen(name);
	if ((*dir = _devfs_make_parent_for_leaf(*dir, name, namelen,
						&leaf_pos)) == NULL) {
		PRINTK("(%s): could not create parent path\n", name);
		return NULL;
	}
	if ((de = _devfs_alloc_entry(name + leaf_pos, namelen - leaf_pos, mode))
	    == NULL) {
		PRINTK("(%s): could not allocate entry\n", name);
		devfs_put(*dir);
		return NULL;
	}
	return de;
}				/*  End Function _devfs_prepare_leaf  */

static devfs_handle_t _devfs_walk_path(struct devfs_entry *dir,
				       const char *name, int namelen,
				       int traverse_symlink)
{
	int next_pos = 0;

	if (dir == NULL)
		dir = _devfs_get_root_entry();
	if (dir == NULL)
		return NULL;
	devfs_get(dir);
	for (; namelen > 0; name += next_pos, namelen -= next_pos) {
		struct devfs_entry *de, *link;

		if (!S_ISDIR(dir->mode)) {
			devfs_put(dir);
			return NULL;