#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));

/*
 * The presence of @parent_inode here tells us whether NFS wants a
 * connectable file handle.  However, we want to make a connectionable
 * file handle unconditionally so that the MDS gets as much of a hint
 * as possible.  That means we only use @parent_dentry to indicate
 * whether nfsd wants a connectable fh, and whether we should indicate
 * failure from a too-small @max_len.
 */
static int ceph_encode_fh(struct inode *inode, u32 *rawfh, int *max_len,
                          struct inode *parent_inode)
{
        int type;
        struct ceph_nfs_fh *fh = (void *)rawfh;
        struct ceph_nfs_confh *cfh = (void *)rawfh;
        int connected_handle_length = sizeof(*cfh)/4;
        int handle_length = sizeof(*fh)/4;
        struct dentry *dentry;
        struct dentry *parent;

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

        dentry = d_find_alias(inode);

        /* if we found an alias, generate a connectable fh */
        if (*max_len >= connected_handle_length && dentry) {
                dout("encode_fh %p connectable\n", dentry);
                spin_lock(&dentry->d_lock);
                parent = dentry->d_parent;
                cfh->ino = ceph_ino(inode);
                cfh->parent_ino = ceph_ino(parent->d_inode);
                cfh->parent_name_hash = ceph_dentry_hash(parent->d_inode,
                                                         dentry);
                *max_len = connected_handle_length;
                type = 2;
                spin_unlock(&dentry->d_lock);
        } else if (*max_len >= handle_length) {
                if (parent_inode) {
                        /* nfsd wants connectable */
                        *max_len = connected_handle_length;
                        type = FILEID_INVALID;
                } else {
                        dout("encode_fh %p\n", dentry);
                        fh->ino = ceph_ino(inode);
                        *max_len = handle_length;
                        type = 1;
                }
        } else {
                *max_len = handle_length;
                type = FILEID_INVALID;
        }
        if (dentry)
                dput(dentry);
        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, int fh_len)
{
        struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
        struct inode *inode;
        struct dentry *dentry;
        struct ceph_vino vino;
        int err;

        if (fh_len < sizeof(*fh) / 4)
                return ERR_PTR(-ESTALE);

        dout("__fh_to_dentry %llx\n", fh->ino);
        vino.ino = fh->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_LOOKUPINO,
                                               USE_ANY_MDS);
                if (IS_ERR(req))
                        return ERR_CAST(req);

                req->r_ino1 = vino;
                req->r_num_caps = 1;
                err = ceph_mdsc_do_request(mdsc, NULL, req);
                inode = req->r_target_inode;
                if (inode)
                        ihold(inode);
                ceph_mdsc_put_request(req);
                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, int fh_len)
{
        struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
        struct inode *inode;
        struct dentry *dentry;
        struct ceph_vino vino;
        int err;

        if (fh_len < sizeof(*cfh) / 4)
                return ERR_PTR(-ESTALE);

        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);
                inode = req->r_target_inode;
                if (inode)
                        ihold(inode);
                ceph_mdsc_put_request(req);
                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,
                                                                fh_len);
        else
                return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw,
                                                                fh_len);
}

/*
 * 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);
        if (fh_len < sizeof(*cfh) / 4)
                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,
};