export.c

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#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 = d_find_alias(inode);
    struct dentry *parent;

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

    /* 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 = 255;
        } else {
            dout("encode_fh %p\n", dentry);
            fh->ino = ceph_ino(inode);
            *max_len = handle_length;
            type = 1;
        }
    } else {
        *max_len = handle_length;
        type = 255;
    }
    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,
};