linux/fs/ceph/export.c
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   1#include <linux/ceph/ceph_debug.h>
   2
   3#include <linux/exportfs.h>
   4#include <linux/slab.h>
   5#include <asm/unaligned.h>
   6
   7#include "super.h"
   8#include "mds_client.h"
   9
  10/*
  11 * NFS export support
  12 *
  13 * NFS re-export of a ceph mount is, at present, only semireliable.
  14 * The basic issue is that the Ceph architectures doesn't lend itself
  15 * well to generating filehandles that will remain valid forever.
  16 *
  17 * So, we do our best.  If you're lucky, your inode will be in the
  18 * client's cache.  If it's not, and you have a connectable fh, then
  19 * the MDS server may be able to find it for you.  Otherwise, you get
  20 * ESTALE.
  21 *
  22 * There are ways to this more reliable, but in the non-connectable fh
  23 * case, we won't every work perfectly, and in the connectable case,
  24 * some changes are needed on the MDS side to work better.
  25 */
  26
  27/*
  28 * Basic fh
  29 */
  30struct ceph_nfs_fh {
  31        u64 ino;
  32} __attribute__ ((packed));
  33
  34/*
  35 * Larger 'connectable' fh that includes parent ino and name hash.
  36 * Use this whenever possible, as it works more reliably.
  37 */
  38struct ceph_nfs_confh {
  39        u64 ino, parent_ino;
  40        u32 parent_name_hash;
  41} __attribute__ ((packed));
  42
  43/*
  44 * The presence of @parent_inode here tells us whether NFS wants a
  45 * connectable file handle.  However, we want to make a connectionable
  46 * file handle unconditionally so that the MDS gets as much of a hint
  47 * as possible.  That means we only use @parent_dentry to indicate
  48 * whether nfsd wants a connectable fh, and whether we should indicate
  49 * failure from a too-small @max_len.
  50 */
  51static int ceph_encode_fh(struct inode *inode, u32 *rawfh, int *max_len,
  52                          struct inode *parent_inode)
  53{
  54        int type;
  55        struct ceph_nfs_fh *fh = (void *)rawfh;
  56        struct ceph_nfs_confh *cfh = (void *)rawfh;
  57        int connected_handle_length = sizeof(*cfh)/4;
  58        int handle_length = sizeof(*fh)/4;
  59        struct dentry *dentry;
  60        struct dentry *parent;
  61
  62        /* don't re-export snaps */
  63        if (ceph_snap(inode) != CEPH_NOSNAP)
  64                return -EINVAL;
  65
  66        dentry = d_find_alias(inode);
  67
  68        /* if we found an alias, generate a connectable fh */
  69        if (*max_len >= connected_handle_length && dentry) {
  70                dout("encode_fh %p connectable\n", dentry);
  71                spin_lock(&dentry->d_lock);
  72                parent = dentry->d_parent;
  73                cfh->ino = ceph_ino(inode);
  74                cfh->parent_ino = ceph_ino(parent->d_inode);
  75                cfh->parent_name_hash = ceph_dentry_hash(parent->d_inode,
  76                                                         dentry);
  77                *max_len = connected_handle_length;
  78                type = 2;
  79                spin_unlock(&dentry->d_lock);
  80        } else if (*max_len >= handle_length) {
  81                if (parent_inode) {
  82                        /* nfsd wants connectable */
  83                        *max_len = connected_handle_length;
  84                        type = FILEID_INVALID;
  85                } else {
  86                        dout("encode_fh %p\n", dentry);
  87                        fh->ino = ceph_ino(inode);
  88                        *max_len = handle_length;
  89                        type = 1;
  90                }
  91        } else {
  92                *max_len = handle_length;
  93                type = FILEID_INVALID;
  94        }
  95        if (dentry)
  96                dput(dentry);
  97        return type;
  98}
  99
 100/*
 101 * convert regular fh to dentry
 102 *
 103 * FIXME: we should try harder by querying the mds for the ino.
 104 */
 105static struct dentry *__fh_to_dentry(struct super_block *sb,
 106                                     struct ceph_nfs_fh *fh, int fh_len)
 107{
 108        struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 109        struct inode *inode;
 110        struct dentry *dentry;
 111        struct ceph_vino vino;
 112        int err;
 113
 114        if (fh_len < sizeof(*fh) / 4)
 115                return ERR_PTR(-ESTALE);
 116
 117        dout("__fh_to_dentry %llx\n", fh->ino);
 118        vino.ino = fh->ino;
 119        vino.snap = CEPH_NOSNAP;
 120        inode = ceph_find_inode(sb, vino);
 121        if (!inode) {
 122                struct ceph_mds_request *req;
 123
 124                req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPINO,
 125                                               USE_ANY_MDS);
 126                if (IS_ERR(req))
 127                        return ERR_CAST(req);
 128
 129                req->r_ino1 = vino;
 130                req->r_num_caps = 1;
 131                err = ceph_mdsc_do_request(mdsc, NULL, req);
 132                inode = req->r_target_inode;
 133                if (inode)
 134                        ihold(inode);
 135                ceph_mdsc_put_request(req);
 136                if (!inode)
 137                        return ERR_PTR(-ESTALE);
 138        }
 139
 140        dentry = d_obtain_alias(inode);
 141        if (IS_ERR(dentry)) {
 142                pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
 143                       fh->ino, inode);
 144                iput(inode);
 145                return dentry;
 146        }
 147        err = ceph_init_dentry(dentry);
 148        if (err < 0) {
 149                iput(inode);
 150                return ERR_PTR(err);
 151        }
 152        dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
 153        return dentry;
 154}
 155
 156/*
 157 * convert connectable fh to dentry
 158 */
 159static struct dentry *__cfh_to_dentry(struct super_block *sb,
 160                                      struct ceph_nfs_confh *cfh, int fh_len)
 161{
 162        struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 163        struct inode *inode;
 164        struct dentry *dentry;
 165        struct ceph_vino vino;
 166        int err;
 167
 168        if (fh_len < sizeof(*cfh) / 4)
 169                return ERR_PTR(-ESTALE);
 170
 171        dout("__cfh_to_dentry %llx (%llx/%x)\n",
 172             cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
 173
 174        vino.ino = cfh->ino;
 175        vino.snap = CEPH_NOSNAP;
 176        inode = ceph_find_inode(sb, vino);
 177        if (!inode) {
 178                struct ceph_mds_request *req;
 179
 180                req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
 181                                               USE_ANY_MDS);
 182                if (IS_ERR(req))
 183                        return ERR_CAST(req);
 184
 185                req->r_ino1 = vino;
 186                req->r_ino2.ino = cfh->parent_ino;
 187                req->r_ino2.snap = CEPH_NOSNAP;
 188                req->r_path2 = kmalloc(16, GFP_NOFS);
 189                snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
 190                req->r_num_caps = 1;
 191                err = ceph_mdsc_do_request(mdsc, NULL, req);
 192                inode = req->r_target_inode;
 193                if (inode)
 194                        ihold(inode);
 195                ceph_mdsc_put_request(req);
 196                if (!inode)
 197                        return ERR_PTR(err ? err : -ESTALE);
 198        }
 199
 200        dentry = d_obtain_alias(inode);
 201        if (IS_ERR(dentry)) {
 202                pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
 203                       cfh->ino, inode);
 204                iput(inode);
 205                return dentry;
 206        }
 207        err = ceph_init_dentry(dentry);
 208        if (err < 0) {
 209                iput(inode);
 210                return ERR_PTR(err);
 211        }
 212        dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
 213        return dentry;
 214}
 215
 216static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
 217                                        int fh_len, int fh_type)
 218{
 219        if (fh_type == 1)
 220                return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw,
 221                                                                fh_len);
 222        else
 223                return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw,
 224                                                                fh_len);
 225}
 226
 227/*
 228 * get parent, if possible.
 229 *
 230 * FIXME: we could do better by querying the mds to discover the
 231 * parent.
 232 */
 233static struct dentry *ceph_fh_to_parent(struct super_block *sb,
 234                                         struct fid *fid,
 235                                        int fh_len, int fh_type)
 236{
 237        struct ceph_nfs_confh *cfh = (void *)fid->raw;
 238        struct ceph_vino vino;
 239        struct inode *inode;
 240        struct dentry *dentry;
 241        int err;
 242
 243        if (fh_type == 1)
 244                return ERR_PTR(-ESTALE);
 245        if (fh_len < sizeof(*cfh) / 4)
 246                return ERR_PTR(-ESTALE);
 247
 248        pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
 249                 cfh->parent_name_hash);
 250
 251        vino.ino = cfh->ino;
 252        vino.snap = CEPH_NOSNAP;
 253        inode = ceph_find_inode(sb, vino);
 254        if (!inode)
 255                return ERR_PTR(-ESTALE);
 256
 257        dentry = d_obtain_alias(inode);
 258        if (IS_ERR(dentry)) {
 259                pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
 260                       cfh->ino, inode);
 261                iput(inode);
 262                return dentry;
 263        }
 264        err = ceph_init_dentry(dentry);
 265        if (err < 0) {
 266                iput(inode);
 267                return ERR_PTR(err);
 268        }
 269        dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
 270        return dentry;
 271}
 272
 273const struct export_operations ceph_export_ops = {
 274        .encode_fh = ceph_encode_fh,
 275        .fh_to_dentry = ceph_fh_to_dentry,
 276        .fh_to_parent = ceph_fh_to_parent,
 277};
 278
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