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 = d_find_alias(inode);
  60        struct dentry *parent;
  61
  62        /* don't re-export snaps */
  63        if (ceph_snap(inode) != CEPH_NOSNAP)
  64                return -EINVAL;
  65
  66        /* if we found an alias, generate a connectable fh */
  67        if (*max_len >= connected_handle_length && dentry) {
  68                dout("encode_fh %p connectable\n", dentry);
  69                spin_lock(&dentry->d_lock);
  70                parent = dentry->d_parent;
  71                cfh->ino = ceph_ino(inode);
  72                cfh->parent_ino = ceph_ino(parent->d_inode);
  73                cfh->parent_name_hash = ceph_dentry_hash(parent->d_inode,
  74                                                         dentry);
  75                *max_len = connected_handle_length;
  76                type = 2;
  77                spin_unlock(&dentry->d_lock);
  78        } else if (*max_len >= handle_length) {
  79                if (parent_inode) {
  80                        /* nfsd wants connectable */
  81                        *max_len = connected_handle_length;
  82                        type = 255;
  83                } else {
  84                        dout("encode_fh %p\n", dentry);
  85                        fh->ino = ceph_ino(inode);
  86                        *max_len = handle_length;
  87                        type = 1;
  88                }
  89        } else {
  90                *max_len = handle_length;
  91                type = 255;
  92        }
  93        if (dentry)
  94                dput(dentry);
  95        return type;
  96}
  97
  98/*
  99 * convert regular fh to dentry
 100 *
 101 * FIXME: we should try harder by querying the mds for the ino.
 102 */
 103static struct dentry *__fh_to_dentry(struct super_block *sb,
 104                                     struct ceph_nfs_fh *fh, int fh_len)
 105{
 106        struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 107        struct inode *inode;
 108        struct dentry *dentry;
 109        struct ceph_vino vino;
 110        int err;
 111
 112        if (fh_len < sizeof(*fh) / 4)
 113                return ERR_PTR(-ESTALE);
 114
 115        dout("__fh_to_dentry %llx\n", fh->ino);
 116        vino.ino = fh->ino;
 117        vino.snap = CEPH_NOSNAP;
 118        inode = ceph_find_inode(sb, vino);
 119        if (!inode) {
 120                struct ceph_mds_request *req;
 121
 122                req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPINO,
 123                                               USE_ANY_MDS);
 124                if (IS_ERR(req))
 125                        return ERR_CAST(req);
 126
 127                req->r_ino1 = vino;
 128                req->r_num_caps = 1;
 129                err = ceph_mdsc_do_request(mdsc, NULL, req);
 130                inode = req->r_target_inode;
 131                if (inode)
 132                        ihold(inode);
 133                ceph_mdsc_put_request(req);
 134                if (!inode)
 135                        return ERR_PTR(-ESTALE);
 136        }
 137
 138        dentry = d_obtain_alias(inode);
 139        if (IS_ERR(dentry)) {
 140                pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
 141                       fh->ino, inode);
 142                iput(inode);
 143                return dentry;
 144        }
 145        err = ceph_init_dentry(dentry);
 146        if (err < 0) {
 147                iput(inode);
 148                return ERR_PTR(err);
 149        }
 150        dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
 151        return dentry;
 152}
 153
 154/*
 155 * convert connectable fh to dentry
 156 */
 157static struct dentry *__cfh_to_dentry(struct super_block *sb,
 158                                      struct ceph_nfs_confh *cfh, int fh_len)
 159{
 160        struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 161        struct inode *inode;
 162        struct dentry *dentry;
 163        struct ceph_vino vino;
 164        int err;
 165
 166        if (fh_len < sizeof(*cfh) / 4)
 167                return ERR_PTR(-ESTALE);
 168
 169        dout("__cfh_to_dentry %llx (%llx/%x)\n",
 170             cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
 171
 172        vino.ino = cfh->ino;
 173        vino.snap = CEPH_NOSNAP;
 174        inode = ceph_find_inode(sb, vino);
 175        if (!inode) {
 176                struct ceph_mds_request *req;
 177
 178                req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
 179                                               USE_ANY_MDS);
 180                if (IS_ERR(req))
 181                        return ERR_CAST(req);
 182
 183                req->r_ino1 = vino;
 184                req->r_ino2.ino = cfh->parent_ino;
 185                req->r_ino2.snap = CEPH_NOSNAP;
 186                req->r_path2 = kmalloc(16, GFP_NOFS);
 187                snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
 188                req->r_num_caps = 1;
 189                err = ceph_mdsc_do_request(mdsc, NULL, req);
 190                inode = req->r_target_inode;
 191                if (inode)
 192                        ihold(inode);
 193                ceph_mdsc_put_request(req);
 194                if (!inode)
 195                        return ERR_PTR(err ? err : -ESTALE);
 196        }
 197
 198        dentry = d_obtain_alias(inode);
 199        if (IS_ERR(dentry)) {
 200                pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
 201                       cfh->ino, inode);
 202                iput(inode);
 203                return dentry;
 204        }
 205        err = ceph_init_dentry(dentry);
 206        if (err < 0) {
 207                iput(inode);
 208                return ERR_PTR(err);
 209        }
 210        dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
 211        return dentry;
 212}
 213
 214static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
 215                                        int fh_len, int fh_type)
 216{
 217        if (fh_type == 1)
 218                return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw,
 219                                                                fh_len);
 220        else
 221                return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw,
 222                                                                fh_len);
 223}
 224
 225/*
 226 * get parent, if possible.
 227 *
 228 * FIXME: we could do better by querying the mds to discover the
 229 * parent.
 230 */
 231static struct dentry *ceph_fh_to_parent(struct super_block *sb,
 232                                         struct fid *fid,
 233                                        int fh_len, int fh_type)
 234{
 235        struct ceph_nfs_confh *cfh = (void *)fid->raw;
 236        struct ceph_vino vino;
 237        struct inode *inode;
 238        struct dentry *dentry;
 239        int err;
 240
 241        if (fh_type == 1)
 242                return ERR_PTR(-ESTALE);
 243        if (fh_len < sizeof(*cfh) / 4)
 244                return ERR_PTR(-ESTALE);
 245
 246        pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
 247                 cfh->parent_name_hash);
 248
 249        vino.ino = cfh->ino;
 250        vino.snap = CEPH_NOSNAP;
 251        inode = ceph_find_inode(sb, vino);
 252        if (!inode)
 253                return ERR_PTR(-ESTALE);
 254
 255        dentry = d_obtain_alias(inode);
 256        if (IS_ERR(dentry)) {
 257                pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
 258                       cfh->ino, inode);
 259                iput(inode);
 260                return dentry;
 261        }
 262        err = ceph_init_dentry(dentry);
 263        if (err < 0) {
 264                iput(inode);
 265                return ERR_PTR(err);
 266        }
 267        dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
 268        return dentry;
 269}
 270
 271const struct export_operations ceph_export_ops = {
 272        .encode_fh = ceph_encode_fh,
 273        .fh_to_dentry = ceph_fh_to_dentry,
 274        .fh_to_parent = ceph_fh_to_parent,
 275};
 276
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