fs/ceph/export.c

   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  */
  30 struct 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  */
  38 struct ceph_nfs_confh {
  39         u64 ino, parent_ino;
  40         u32 parent_name_hash;
  41 } __attribute__ ((packed));
  42
  43 static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
  44                           int connectable)
  45 {
  46         int type;
  47         struct ceph_nfs_fh *fh = (void *)rawfh;
  48         struct ceph_nfs_confh *cfh = (void *)rawfh;
  49         struct dentry *parent;
  50         struct inode *inode = dentry->d_inode;
  51         int connected_handle_length = sizeof(*cfh)/4;
  52         int handle_length = sizeof(*fh)/4;
  53
  54         /* don't re-export snaps */
  55         if (ceph_snap(inode) != CEPH_NOSNAP)
  56                 return -EINVAL;
  57
  58         spin_lock(&dentry->d_lock);
  59         parent = dget(dentry->d_parent);
  60         spin_unlock(&dentry->d_lock);
  61
  62         if (*max_len >= connected_handle_length) {
  63                 dout("encode_fh %p connectable\n", dentry);
  64                 cfh->ino = ceph_ino(dentry->d_inode);
  65                 cfh->parent_ino = ceph_ino(parent->d_inode);
  66                 cfh->parent_name_hash = ceph_dentry_hash(parent->d_inode,
  67                                                          dentry);
  68                 *max_len = connected_handle_length;
  69                 type = 2;
  70         } else if (*max_len >= handle_length) {
  71                 if (connectable) {
  72                         *max_len = connected_handle_length;
  73                         type = 255;
  74                 } else {
  75                         dout("encode_fh %p\n", dentry);
  76                         fh->ino = ceph_ino(dentry->d_inode);
  77                         *max_len = handle_length;
  78                         type = 1;
  79                 }
  80         } else {
  81                 *max_len = handle_length;
  82                 type = 255;
  83         }
  84         dput(parent);
  85         return type;
  86 }
  87
  88 /*
  89  * convert regular fh to dentry
  90  *
  91  * FIXME: we should try harder by querying the mds for the ino.
  92  */
  93 static struct dentry *__fh_to_dentry(struct super_block *sb,
  94                                      struct ceph_nfs_fh *fh)
  95 {
  96         struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
  97         struct inode *inode;
  98         struct dentry *dentry;
  99         struct ceph_vino vino;
 100         int err;
 101
 102         dout("__fh_to_dentry %llx\n", fh->ino);
 103         vino.ino = fh->ino;
 104         vino.snap = CEPH_NOSNAP;
 105         inode = ceph_find_inode(sb, vino);
 106         if (!inode) {
 107                 struct ceph_mds_request *req;
 108
 109                 req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPINO,
 110                                                USE_ANY_MDS);
 111                 if (IS_ERR(req))
 112                         return ERR_CAST(req);
 113
 114                 req->r_ino1 = vino;
 115                 req->r_num_caps = 1;
 116                 err = ceph_mdsc_do_request(mdsc, NULL, req);
 117                 inode = req->r_target_inode;
 118                 if (inode)
 119                         ihold(inode);
 120                 ceph_mdsc_put_request(req);
 121                 if (!inode)
 122                         return ERR_PTR(-ESTALE);
 123         }
 124
 125         dentry = d_obtain_alias(inode);
 126         if (IS_ERR(dentry)) {
 127                 pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
 128                        fh->ino, inode);
 129                 iput(inode);
 130                 return dentry;
 131         }
 132         err = ceph_init_dentry(dentry);
 133         if (err < 0) {
 134                 iput(inode);
 135                 return ERR_PTR(err);
 136         }
 137         dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
 138         return dentry;
 139 }
 140
 141 /*
 142  * convert connectable fh to dentry
 143  */
 144 static struct dentry *__cfh_to_dentry(struct super_block *sb,
 145                                       struct ceph_nfs_confh *cfh)
 146 {
 147         struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 148         struct inode *inode;
 149         struct dentry *dentry;
 150         struct ceph_vino vino;
 151         int err;
 152
 153         dout("__cfh_to_dentry %llx (%llx/%x)\n",
 154              cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
 155
 156         vino.ino = cfh->ino;
 157         vino.snap = CEPH_NOSNAP;
 158         inode = ceph_find_inode(sb, vino);
 159         if (!inode) {
 160                 struct ceph_mds_request *req;
 161
 162                 req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
 163                                                USE_ANY_MDS);
 164                 if (IS_ERR(req))
 165                         return ERR_CAST(req);
 166
 167                 req->r_ino1 = vino;
 168                 req->r_ino2.ino = cfh->parent_ino;
 169                 req->r_ino2.snap = CEPH_NOSNAP;
 170                 req->r_path2 = kmalloc(16, GFP_NOFS);
 171                 snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
 172                 req->r_num_caps = 1;
 173                 err = ceph_mdsc_do_request(mdsc, NULL, req);
 174                 inode = req->r_target_inode;
 175                 if (inode)
 176                         ihold(inode);
 177                 ceph_mdsc_put_request(req);
 178                 if (!inode)
 179                         return ERR_PTR(err ? err : -ESTALE);
 180         }
 181
 182         dentry = d_obtain_alias(inode);
 183         if (IS_ERR(dentry)) {
 184                 pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
 185                        cfh->ino, inode);
 186                 iput(inode);
 187                 return dentry;
 188         }
 189         err = ceph_init_dentry(dentry);
 190         if (err < 0) {
 191                 iput(inode);
 192                 return ERR_PTR(err);
 193         }
 194         dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
 195         return dentry;
 196 }
 197
 198 static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
 199                                         int fh_len, int fh_type)
 200 {
 201         if (fh_type == 1)
 202                 return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw);
 203         else
 204                 return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw);
 205 }
 206
 207 /*
 208  * get parent, if possible.
 209  *
 210  * FIXME: we could do better by querying the mds to discover the
 211  * parent.
 212  */
 213 static struct dentry *ceph_fh_to_parent(struct super_block *sb,
 214                                          struct fid *fid,
 215                                         int fh_len, int fh_type)
 216 {
 217         struct ceph_nfs_confh *cfh = (void *)fid->raw;
 218         struct ceph_vino vino;
 219         struct inode *inode;
 220         struct dentry *dentry;
 221         int err;
 222
 223         if (fh_type == 1)
 224                 return ERR_PTR(-ESTALE);
 225
 226         pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
 227                  cfh->parent_name_hash);
 228
 229         vino.ino = cfh->ino;
 230         vino.snap = CEPH_NOSNAP;
 231         inode = ceph_find_inode(sb, vino);
 232         if (!inode)
 233                 return ERR_PTR(-ESTALE);
 234
 235         dentry = d_obtain_alias(inode);
 236         if (IS_ERR(dentry)) {
 237                 pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
 238                        cfh->ino, inode);
 239                 iput(inode);
 240                 return dentry;
 241         }
 242         err = ceph_init_dentry(dentry);
 243         if (err < 0) {
 244                 iput(inode);
 245                 return ERR_PTR(err);
 246         }
 247         dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
 248         return dentry;
 249 }
 250
 251 const struct export_operations ceph_export_ops = {
 252         .encode_fh = ceph_encode_fh,
 253         .fh_to_dentry = ceph_fh_to_dentry,
 254         .fh_to_parent = ceph_fh_to_parent,
 255 };