text: #include "ceph_debug.h"
  
  #include <linux/exportfs.h>
  #include <linux/slab.h>
  #include <asm/unaligned.h>
  
  #include "super.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)
  {
  	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 type;
  
  	/* don't re-export snaps */
  	if (ceph_snap(inode) != CEPH_NOSNAP)
  		return -EINVAL;
  
  	if (*max_len >= sizeof(*cfh)) {
  		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 = sizeof(*cfh);
  		type = 2;
  	} else if (*max_len > sizeof(*fh)) {
  		if (connectable)
  			return -ENOSPC;
  		dout("encode_fh %p\n", dentry);
  		fh->ino = ceph_ino(dentry->d_inode);
  		*max_len = sizeof(*fh);
  		type = 1;
  	} else {
  		return -ENOSPC;
  	}
  	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,
  };
  