export.c

#include <linux/ceph/ceph_debug.h>

#include <linux/exportfs.h>
#include <linux/slab.h>
#include <asm/unaligned.h>

#include "super.h"
#include "mds_client.h"

/*
 * NFS export support
 *
 * NFS re-export of a ceph mount is, at present, only semireliable.
 * The basic issue is that the Ceph architectures doesn't lend itself
 * well to generating filehandles that will remain valid forever.
 *
 * So, we do our best.  If you're lucky, your inode will be in the
 * client's cache.  If it's not, and you have a connectable fh, then
 * the MDS server may be able to find it for you.  Otherwise, you get
 * ESTALE.
 *
 * There are ways to this more reliable, but in the non-connectable fh
 * case, we won't every work perfectly, and in the connectable case,
 * some changes are needed on the MDS side to work better.
 */

/*
 * Basic fh
 */
struct ceph_nfs_fh {
	u64 ino;
} __attribute__ ((packed));

/*
 * Larger 'connectable' fh that includes parent ino and name hash.
 * Use this whenever possible, as it works more reliably.
 */
struct ceph_nfs_confh {
	u64 ino, parent_ino;
	u32 parent_name_hash;
} __attribute__ ((packed));

static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
			  int connectable)
{
	int type;
	struct ceph_nfs_fh *fh = (void *)rawfh;
	struct ceph_nfs_confh *cfh = (void *)rawfh;
	struct dentry *parent = dentry->d_parent;
	struct inode *inode = dentry->d_inode;
	int connected_handle_length = sizeof(*cfh)/4;
	int handle_length = sizeof(*fh)/4;

	/* don't re-export snaps */
	if (ceph_snap(inode) != CEPH_NOSNAP)
		return -EINVAL;

	if (*max_len >= connected_handle_length) {
		dout("encode_fh %p connectable\n", dentry);
		cfh->ino = ceph_ino(dentry->d_inode);
		cfh->parent_ino = ceph_ino(parent->d_inode);
		cfh->parent_name_hash = parent->d_name.hash;
		*max_len = connected_handle_length;
		type = 2;
	} else if (*max_len >= handle_length) {
		if (connectable) {
			*max_len = connected_handle_length;
			return 255;
		}
		dout("encode_fh %p\n", dentry);
		fh->ino = ceph_ino(dentry->d_inode);
		*max_len = handle_length;
		type = 1;
	} else {
		*max_len = handle_length;
		return 255;
	}
	return type;
}

/*
 * convert regular fh to dentry
 *
 * FIXME: we should try harder by querying the mds for the ino.
 */
static struct dentry *__fh_to_dentry(struct super_block *sb,
				     struct ceph_nfs_fh *fh)
{
	struct inode *inode;
	struct dentry *dentry;
	struct ceph_vino vino;
	int err;

	dout("__fh_to_dentry %llx\n", fh->ino);
	vino.ino = fh->ino;
	vino.snap = CEPH_NOSNAP;
	inode = ceph_find_inode(sb, vino);
	if (!inode)
		return ERR_PTR(-ESTALE);

	dentry = d_obtain_alias(inode);
	if (IS_ERR(dentry)) {
		pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
		       fh->ino, inode);
		iput(inode);
		return dentry;
	}
	err = ceph_init_dentry(dentry);

	if (err < 0) {
		iput(inode);
		return ERR_PTR(err);
	}
	dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
	return dentry;
}

/*
 * convert connectable fh to dentry
 */
static struct dentry *__cfh_to_dentry(struct super_block *sb,
				      struct ceph_nfs_confh *cfh)
{
	struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
	struct inode *inode;
	struct dentry *dentry;
	struct ceph_vino vino;
	int err;

	dout("__cfh_to_dentry %llx (%llx/%x)\n",
	     cfh->ino, cfh->parent_ino, cfh->parent_name_hash);

	vino.ino = cfh->ino;
	vino.snap = CEPH_NOSNAP;
	inode = ceph_find_inode(sb, vino);
	if (!inode) {
		struct ceph_mds_request *req;

		req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
					       USE_ANY_MDS);
		if (IS_ERR(req))
			return ERR_CAST(req);

		req->r_ino1 = vino;
		req->r_ino2.ino = cfh->parent_ino;
		req->r_ino2.snap = CEPH_NOSNAP;
		req->r_path2 = kmalloc(16, GFP_NOFS);
		snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
		req->r_num_caps = 1;
		err = ceph_mdsc_do_request(mdsc, NULL, req);
		ceph_mdsc_put_request(req);
		inode = ceph_find_inode(sb, vino);
		if (!inode)
			return ERR_PTR(err ? err : -ESTALE);
	}

	dentry = d_obtain_alias(inode);
	if (IS_ERR(dentry)) {
		pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
		       cfh->ino, inode);
		iput(inode);
		return dentry;
	}
	err = ceph_init_dentry(dentry);
	if (err < 0) {
		iput(inode);
		return ERR_PTR(err);
	}
	dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
	return dentry;
}

static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
					int fh_len, int fh_type)
{
	if (fh_type == 1)
		return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw);
	else
		return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw);
}

/*
 * get parent, if possible.
 *
 * FIXME: we could do better by querying the mds to discover the
 * parent.
 */
static struct dentry *ceph_fh_to_parent(struct super_block *sb,
					 struct fid *fid,
					int fh_len, int fh_type)
{
	struct ceph_nfs_confh *cfh = (void *)fid->raw;
	struct ceph_vino vino;
	struct inode *inode;
	struct dentry *dentry;
	int err;

	if (fh_type == 1)
		return ERR_PTR(-ESTALE);

	pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
		 cfh->parent_name_hash);

	vino.ino = cfh->ino;
	vino.snap = CEPH_NOSNAP;
	inode = ceph_find_inode(sb, vino);
	if (!inode)
		return ERR_PTR(-ESTALE);

	dentry = d_obtain_alias(inode);
	if (IS_ERR(dentry)) {
		pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
		       cfh->ino, inode);
		iput(inode);
		return dentry;
	}
	err = ceph_init_dentry(dentry);
	if (err < 0) {
		iput(inode);
		return ERR_PTR(err);
	}
	dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
	return dentry;
}

const struct export_operations ceph_export_ops = {
	.encode_fh = ceph_encode_fh,
	.fh_to_dentry = ceph_fh_to_dentry,
	.fh_to_parent = ceph_fh_to_parent,
};