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 /*
  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  */
  51 static 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 = 255;
  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 = 255;
  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  */
 105 static 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  */
 159 static 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
 216 static 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  */
 233 static 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
 273 const 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 };