1 files changed, 549 insertions, 0 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
new file mode 100644
index 0000000..f90b295
--- /dev/null
+++ b/fs/libfs.c
@@ -0,0 +1,549 @@
+/*
+ *	fs/libfs.c
+ *	Library for filesystems writers.
+ */
+
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <linux/mount.h>
+#include <linux/vfs.h>
+#include <asm/uaccess.h>
+
+int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
+		   struct kstat *stat)
+{
+	struct inode *inode = dentry->d_inode;
+	generic_fillattr(inode, stat);
+	stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
+	return 0;
+}
+
+int simple_statfs(struct super_block *sb, struct kstatfs *buf)
+{
+	buf->f_type = sb->s_magic;
+	buf->f_bsize = PAGE_CACHE_SIZE;
+	buf->f_namelen = NAME_MAX;
+	return 0;
+}
+
+/*
+ * Retaining negative dentries for an in-memory filesystem just wastes
+ * memory and lookup time: arrange for them to be deleted immediately.
+ */
+static int simple_delete_dentry(struct dentry *dentry)
+{
+	return 1;
+}
+
+/*
+ * Lookup the data. This is trivial - if the dentry didn't already
+ * exist, we know it is negative.  Set d_op to delete negative dentries.
+ */
+struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
+{
+	static struct dentry_operations simple_dentry_operations = {
+		.d_delete = simple_delete_dentry,
+	};
+
+	if (dentry->d_name.len > NAME_MAX)
+		return ERR_PTR(-ENAMETOOLONG);
+	dentry->d_op = &simple_dentry_operations;
+	d_add(dentry, NULL);
+	return NULL;
+}
+
+int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
+{
+	return 0;
+}
+ 
+int dcache_dir_open(struct inode *inode, struct file *file)
+{
+	static struct qstr cursor_name = {.len = 1, .name = "."};
+
+	file->private_data = d_alloc(file->f_dentry, &cursor_name);
+
+	return file->private_data ? 0 : -ENOMEM;
+}
+
+int dcache_dir_close(struct inode *inode, struct file *file)
+{
+	dput(file->private_data);
+	return 0;
+}
+
+loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
+{
+	down(&file->f_dentry->d_inode->i_sem);
+	switch (origin) {
+		case 1:
+			offset += file->f_pos;
+		case 0:
+			if (offset >= 0)
+				break;
+		default:
+			up(&file->f_dentry->d_inode->i_sem);
+			return -EINVAL;
+	}
+	if (offset != file->f_pos) {
+		file->f_pos = offset;
+		if (file->f_pos >= 2) {
+			struct list_head *p;
+			struct dentry *cursor = file->private_data;
+			loff_t n = file->f_pos - 2;
+
+			spin_lock(&dcache_lock);
+			list_del(&cursor->d_child);
+			p = file->f_dentry->d_subdirs.next;
+			while (n && p != &file->f_dentry->d_subdirs) {
+				struct dentry *next;
+				next = list_entry(p, struct dentry, d_child);
+				if (!d_unhashed(next) && next->d_inode)
+					n--;
+				p = p->next;
+			}
+			list_add_tail(&cursor->d_child, p);
+			spin_unlock(&dcache_lock);
+		}
+	}
+	up(&file->f_dentry->d_inode->i_sem);
+	return offset;
+}
+
+/* Relationship between i_mode and the DT_xxx types */
+static inline unsigned char dt_type(struct inode *inode)
+{
+	return (inode->i_mode >> 12) & 15;
+}
+
+/*
+ * Directory is locked and all positive dentries in it are safe, since
+ * for ramfs-type trees they can't go away without unlink() or rmdir(),
+ * both impossible due to the lock on directory.
+ */
+
+int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
+{
+	struct dentry *dentry = filp->f_dentry;
+	struct dentry *cursor = filp->private_data;
+	struct list_head *p, *q = &cursor->d_child;
+	ino_t ino;
+	int i = filp->f_pos;
+
+	switch (i) {
+		case 0:
+			ino = dentry->d_inode->i_ino;
+			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
+				break;
+			filp->f_pos++;
+			i++;
+			/* fallthrough */
+		case 1:
+			ino = parent_ino(dentry);
+			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
+				break;
+			filp->f_pos++;
+			i++;
+			/* fallthrough */
+		default:
+			spin_lock(&dcache_lock);
+			if (filp->f_pos == 2) {
+				list_del(q);
+				list_add(q, &dentry->d_subdirs);
+			}
+			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
+				struct dentry *next;
+				next = list_entry(p, struct dentry, d_child);
+				if (d_unhashed(next) || !next->d_inode)
+					continue;
+
+				spin_unlock(&dcache_lock);
+				if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
+					return 0;
+				spin_lock(&dcache_lock);
+				/* next is still alive */
+				list_del(q);
+				list_add(q, p);
+				p = q;
+				filp->f_pos++;
+			}
+			spin_unlock(&dcache_lock);
+	}
+	return 0;
+}
+
+ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
+{
+	return -EISDIR;
+}
+
+struct file_operations simple_dir_operations = {
+	.open		= dcache_dir_open,
+	.release	= dcache_dir_close,
+	.llseek		= dcache_dir_lseek,
+	.read		= generic_read_dir,
+	.readdir	= dcache_readdir,
+};
+
+struct inode_operations simple_dir_inode_operations = {
+	.lookup		= simple_lookup,
+};
+
+/*
+ * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
+ * will never be mountable)
+ */
+struct super_block *
+get_sb_pseudo(struct file_system_type *fs_type, char *name,
+	struct super_operations *ops, unsigned long magic)
+{
+	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
+	static struct super_operations default_ops = {.statfs = simple_statfs};
+	struct dentry *dentry;
+	struct inode *root;
+	struct qstr d_name = {.name = name, .len = strlen(name)};
+
+	if (IS_ERR(s))
+		return s;
+
+	s->s_flags = MS_NOUSER;
+	s->s_maxbytes = ~0ULL;
+	s->s_blocksize = 1024;
+	s->s_blocksize_bits = 10;
+	s->s_magic = magic;
+	s->s_op = ops ? ops : &default_ops;
+	s->s_time_gran = 1;
+	root = new_inode(s);
+	if (!root)
+		goto Enomem;
+	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
+	root->i_uid = root->i_gid = 0;
+	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
+	dentry = d_alloc(NULL, &d_name);
+	if (!dentry) {
+		iput(root);
+		goto Enomem;
+	}
+	dentry->d_sb = s;
+	dentry->d_parent = dentry;
+	d_instantiate(dentry, root);
+	s->s_root = dentry;
+	s->s_flags |= MS_ACTIVE;
+	return s;
+
+Enomem:
+	up_write(&s->s_umount);
+	deactivate_super(s);
+	return ERR_PTR(-ENOMEM);
+}
+
+int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = old_dentry->d_inode;
+
+	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+	inode->i_nlink++;
+	atomic_inc(&inode->i_count);
+	dget(dentry);
+	d_instantiate(dentry, inode);
+	return 0;
+}
+
+static inline int simple_positive(struct dentry *dentry)
+{
+	return dentry->d_inode && !d_unhashed(dentry);
+}
+
+int simple_empty(struct dentry *dentry)
+{
+	struct dentry *child;
+	int ret = 0;
+
+	spin_lock(&dcache_lock);
+	list_for_each_entry(child, &dentry->d_subdirs, d_child)
+		if (simple_positive(child))
+			goto out;
+	ret = 1;
+out:
+	spin_unlock(&dcache_lock);
+	return ret;
+}
+
+int simple_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = dentry->d_inode;
+
+	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+	inode->i_nlink--;
+	dput(dentry);
+	return 0;
+}
+
+int simple_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	if (!simple_empty(dentry))
+		return -ENOTEMPTY;
+
+	dentry->d_inode->i_nlink--;
+	simple_unlink(dir, dentry);
+	dir->i_nlink--;
+	return 0;
+}
+
+int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
+		struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct inode *inode = old_dentry->d_inode;
+	int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
+
+	if (!simple_empty(new_dentry))
+		return -ENOTEMPTY;
+
+	if (new_dentry->d_inode) {
+		simple_unlink(new_dir, new_dentry);
+		if (they_are_dirs)
+			old_dir->i_nlink--;
+	} else if (they_are_dirs) {
+		old_dir->i_nlink--;
+		new_dir->i_nlink++;
+	}
+
+	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
+		new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
+
+	return 0;
+}
+
+int simple_readpage(struct file *file, struct page *page)
+{
+	void *kaddr;
+
+	if (PageUptodate(page))
+		goto out;
+
+	kaddr = kmap_atomic(page, KM_USER0);
+	memset(kaddr, 0, PAGE_CACHE_SIZE);
+	kunmap_atomic(kaddr, KM_USER0);
+	flush_dcache_page(page);
+	SetPageUptodate(page);
+out:
+	unlock_page(page);
+	return 0;
+}
+
+int simple_prepare_write(struct file *file, struct page *page,
+			unsigned from, unsigned to)
+{
+	if (!PageUptodate(page)) {
+		if (to - from != PAGE_CACHE_SIZE) {
+			void *kaddr = kmap_atomic(page, KM_USER0);
+			memset(kaddr, 0, from);
+			memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
+			flush_dcache_page(page);
+			kunmap_atomic(kaddr, KM_USER0);
+		}
+		SetPageUptodate(page);
+	}
+	return 0;
+}
+
+int simple_commit_write(struct file *file, struct page *page,
+			unsigned offset, unsigned to)
+{
+	struct inode *inode = page->mapping->host;
+	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
+
+	/*
+	 * No need to use i_size_read() here, the i_size
+	 * cannot change under us because we hold the i_sem.
+	 */
+	if (pos > inode->i_size)
+		i_size_write(inode, pos);
+	set_page_dirty(page);
+	return 0;
+}
+
+int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
+{
+	static struct super_operations s_ops = {.statfs = simple_statfs};
+	struct inode *inode;
+	struct dentry *root;
+	struct dentry *dentry;
+	int i;
+
+	s->s_blocksize = PAGE_CACHE_SIZE;
+	s->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	s->s_magic = magic;
+	s->s_op = &s_ops;
+	s->s_time_gran = 1;
+
+	inode = new_inode(s);
+	if (!inode)
+		return -ENOMEM;
+	inode->i_mode = S_IFDIR | 0755;
+	inode->i_uid = inode->i_gid = 0;
+	inode->i_blksize = PAGE_CACHE_SIZE;
+	inode->i_blocks = 0;
+	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	inode->i_op = &simple_dir_inode_operations;
+	inode->i_fop = &simple_dir_operations;
+	root = d_alloc_root(inode);
+	if (!root) {
+		iput(inode);
+		return -ENOMEM;
+	}
+	for (i = 0; !files->name || files->name[0]; i++, files++) {
+		if (!files->name)
+			continue;
+		dentry = d_alloc_name(root, files->name);
+		if (!dentry)
+			goto out;
+		inode = new_inode(s);
+		if (!inode)
+			goto out;
+		inode->i_mode = S_IFREG | files->mode;
+		inode->i_uid = inode->i_gid = 0;
+		inode->i_blksize = PAGE_CACHE_SIZE;
+		inode->i_blocks = 0;
+		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+		inode->i_fop = files->ops;
+		inode->i_ino = i;
+		d_add(dentry, inode);
+	}
+	s->s_root = root;
+	return 0;
+out:
+	d_genocide(root);
+	dput(root);
+	return -ENOMEM;
+}
+
+static DEFINE_SPINLOCK(pin_fs_lock);
+
+int simple_pin_fs(char *name, struct vfsmount **mount, int *count)
+{
+	struct vfsmount *mnt = NULL;
+	spin_lock(&pin_fs_lock);
+	if (unlikely(!*mount)) {
+		spin_unlock(&pin_fs_lock);
+		mnt = do_kern_mount(name, 0, name, NULL);
+		if (IS_ERR(mnt))
+			return PTR_ERR(mnt);
+		spin_lock(&pin_fs_lock);
+		if (!*mount)
+			*mount = mnt;
+	}
+	mntget(*mount);
+	++*count;
+	spin_unlock(&pin_fs_lock);
+	mntput(mnt);
+	return 0;
+}
+
+void simple_release_fs(struct vfsmount **mount, int *count)
+{
+	struct vfsmount *mnt;
+	spin_lock(&pin_fs_lock);
+	mnt = *mount;
+	if (!--*count)
+		*mount = NULL;
+	spin_unlock(&pin_fs_lock);
+	mntput(mnt);
+}
+
+ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
+				const void *from, size_t available)
+{
+	loff_t pos = *ppos;
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	if (copy_to_user(to, from + pos, count))
+		return -EFAULT;
+	*ppos = pos + count;
+	return count;
+}
+
+/*
+ * Transaction based IO.
+ * The file expects a single write which triggers the transaction, and then
+ * possibly a read which collects the result - which is stored in a
+ * file-local buffer.
+ */
+char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
+{
+	struct simple_transaction_argresp *ar;
+	static DEFINE_SPINLOCK(simple_transaction_lock);
+
+	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
+		return ERR_PTR(-EFBIG);
+
+	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
+	if (!ar)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock(&simple_transaction_lock);
+
+	/* only one write allowed per open */
+	if (file->private_data) {
+		spin_unlock(&simple_transaction_lock);
+		free_page((unsigned long)ar);
+		return ERR_PTR(-EBUSY);
+	}
+
+	file->private_data = ar;
+
+	spin_unlock(&simple_transaction_lock);
+
+	if (copy_from_user(ar->data, buf, size))
+		return ERR_PTR(-EFAULT);
+
+	return ar->data;
+}
+
+ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
+{
+	struct simple_transaction_argresp *ar = file->private_data;
+
+	if (!ar)
+		return 0;
+	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
+}
+
+int simple_transaction_release(struct inode *inode, struct file *file)
+{
+	free_page((unsigned long)file->private_data);
+	return 0;
+}
+
+EXPORT_SYMBOL(dcache_dir_close);
+EXPORT_SYMBOL(dcache_dir_lseek);
+EXPORT_SYMBOL(dcache_dir_open);
+EXPORT_SYMBOL(dcache_readdir);
+EXPORT_SYMBOL(generic_read_dir);
+EXPORT_SYMBOL(get_sb_pseudo);
+EXPORT_SYMBOL(simple_commit_write);
+EXPORT_SYMBOL(simple_dir_inode_operations);
+EXPORT_SYMBOL(simple_dir_operations);
+EXPORT_SYMBOL(simple_empty);
+EXPORT_SYMBOL(d_alloc_name);
+EXPORT_SYMBOL(simple_fill_super);
+EXPORT_SYMBOL(simple_getattr);
+EXPORT_SYMBOL(simple_link);
+EXPORT_SYMBOL(simple_lookup);
+EXPORT_SYMBOL(simple_pin_fs);
+EXPORT_SYMBOL(simple_prepare_write);
+EXPORT_SYMBOL(simple_readpage);
+EXPORT_SYMBOL(simple_release_fs);
+EXPORT_SYMBOL(simple_rename);
+EXPORT_SYMBOL(simple_rmdir);
+EXPORT_SYMBOL(simple_statfs);
+EXPORT_SYMBOL(simple_sync_file);
+EXPORT_SYMBOL(simple_unlink);
+EXPORT_SYMBOL(simple_read_from_buffer);
+EXPORT_SYMBOL(simple_transaction_get);
+EXPORT_SYMBOL(simple_transaction_read);
+EXPORT_SYMBOL(simple_transaction_release);