path: root/fs/libfs.c

/*
 *	fs/libfs.c
 *	Library for filesystems writers.
 */

#include <linux/blkdev.h>
#include <linux/export.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/quotaops.h>
#include <linux/mutex.h>
#include <linux/namei.h>
#include <linux/exportfs.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h> /* sync_mapping_buffers */

#include <linux/uaccess.h>

#include "internal.h"

int simple_getattr(const struct path *path, struct kstat *stat,
		   u32 request_mask, unsigned int query_flags)
{
	struct inode *inode = d_inode(path->dentry);
	generic_fillattr(inode, stat);
	stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
	return 0;
}
EXPORT_SYMBOL(simple_getattr);

int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	buf->f_type = dentry->d_sb->s_magic;
	buf->f_bsize = PAGE_SIZE;
	buf->f_namelen = NAME_MAX;
	return 0;
}
EXPORT_SYMBOL(simple_statfs);

/*
 * Retaining negative dentries for an in-memory filesystem just wastes
 * memory and lookup time: arrange for them to be deleted immediately.
 */
int always_delete_dentry(const struct dentry *dentry)
{
	return 1;
}
EXPORT_SYMBOL(always_delete_dentry);

const struct dentry_operations simple_dentry_operations = {
	.d_delete = always_delete_dentry,
};
EXPORT_SYMBOL(simple_dentry_operations);

/*
 * 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, unsigned int flags)
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	if (!dentry->d_sb->s_d_op)
		d_set_d_op(dentry, &simple_dentry_operations);
	d_add(dentry, NULL);
	return NULL;
}
EXPORT_SYMBOL(simple_lookup);

int dcache_dir_open(struct inode *inode, struct file *file)
{
	file->private_data = d_alloc_cursor(file->f_path.dentry);

	return file->private_data ? 0 : -ENOMEM;
}
EXPORT_SYMBOL(dcache_dir_open);

int dcache_dir_close(struct inode *inode, struct file *file)
{
	dput(file->private_data);
	return 0;
}
EXPORT_SYMBOL(dcache_dir_close);

/* parent is locked at least shared */
static struct dentry *next_positive(struct dentry *parent,
				    struct list_head *from,
				    int count)
{
	unsigned *seq = &parent->d_inode->i_dir_seq, n;
	struct dentry *res;
	struct list_head *p;
	bool skipped;
	int i;

retry:
	i = count;
	skipped = false;
	n = smp_load_acquire(seq) & ~1;
	res = NULL;
	rcu_read_lock();
	for (p = from->next; p != &parent->d_subdirs; p = p->next) {
		struct dentry *d = list_entry(p, struct dentry, d_child);
		if (!simple_positive(d)) {
			skipped = true;
		} else if (!--i) {
			res = d;
			break;
		}
	}
	rcu_read_unlock();
	if (skipped) {
		smp_rmb();
		if (unlikely(*seq != n))
			goto retry;
	}
	return res;
}

static void move_cursor(struct dentry *cursor, struct list_head *after)
{