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 = 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         return type;
  94 }
  95
  96 /*
  97  * convert regular fh to dentry
  98  *
  99  * FIXME: we should try harder by querying the mds for the ino.
 100  */
 101 static struct dentry *__fh_to_dentry(struct super_block *sb,
 102                                      struct ceph_nfs_fh *fh, int fh_len)
 103 {
 104         struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 105         struct inode *inode;
 106         struct dentry *dentry;
 107         struct ceph_vino vino;
 108         int err;
 109
 110         if (fh_len < sizeof(*fh) / 4)
 111                 return ERR_PTR(-ESTALE);
 112
 113         dout("__fh_to_dentry %llx\n", fh->ino);
 114         vino.ino = fh->ino;
 115         vino.snap = CEPH_NOSNAP;
 116         inode = ceph_find_inode(sb, vino);
 117         if (!inode) {
 118                 struct ceph_mds_request *req;
 119
 120                 req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPINO,
 121                                                USE_ANY_MDS);
 122                 if (IS_ERR(req))
 123                         return ERR_CAST(req);
 124
 125                 req->r_ino1 = vino;
 126                 req->r_num_caps = 1;
 127                 err = ceph_mdsc_do_request(mdsc, NULL, req);
 128                 inode = req->r_target_inode;
 129                 if (inode)
 130                         ihold(inode);
 131                 ceph_mdsc_put_request(req);
 132                 if (!inode)
 133                         return ERR_PTR(-ESTALE);
 134         }
 135
 136         dentry = d_obtain_alias(inode);
 137         if (IS_ERR(dentry)) {
 138                 pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
 139                        fh->ino, inode);
 140                 iput(inode);
 141                 return dentry;
 142         }
 143         err = ceph_init_dentry(dentry);
 144         if (err < 0) {
 145                 iput(inode);
 146                 return ERR_PTR(err);
 147         }
 148         dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
 149         return dentry;
 150 }
 151
 152 /*
 153  * convert connectable fh to dentry
 154  */
 155 static struct dentry *__cfh_to_dentry(struct super_block *sb,
 156                                       struct ceph_nfs_confh *cfh, int fh_len)
 157 {
 158         struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 159         struct inode *inode;
 160         struct dentry *dentry;
 161         struct ceph_vino vino;
 162         int err;
 163
 164         if (fh_len < sizeof(*cfh) / 4)
 165                 return ERR_PTR(-ESTALE);
 166
 167         dout("__cfh_to_dentry %llx (%llx/%x)\n",
 168              cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
 169
 170         vino.ino = cfh->ino;
 171         vino.snap = CEPH_NOSNAP;
 172         inode = ceph_find_inode(sb, vino);
 173         if (!inode) {
 174                 struct ceph_mds_request *req;
 175
 176                 req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
 177                                                USE_ANY_MDS);
 178                 if (IS_ERR(req))
 179                         return ERR_CAST(req);
 180
 181                 req->r_ino1 = vino;
 182                 req->r_ino2.ino = cfh->parent_ino;
 183                 req->r_ino2.snap = CEPH_NOSNAP;
 184                 req->r_path2 = kmalloc(16, GFP_NOFS);
 185                 snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
 186                 req->r_num_caps = 1;
 187                 err = ceph_mdsc_do_request(mdsc, NULL, req);
 188                 inode = req->r_target_inode;
 189                 if (inode)
 190                         ihold(inode);
 191                 ceph_mdsc_put_request(req);
 192                 if (!inode)
 193                         return ERR_PTR(err ? err : -ESTALE);
 194         }
 195
 196         dentry = d_obtain_alias(inode);
 197         if (IS_ERR(dentry)) {
 198                 pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
 199                        cfh->ino, inode);
 200                 iput(inode);
 201                 return dentry;
 202         }
 203         err = ceph_init_dentry(dentry);
 204         if (err < 0) {
 205                 iput(inode);
 206                 return ERR_PTR(err);
 207         }
 208         dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
 209         return dentry;
 210 }
 211
 212 static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
 213                                         int fh_len, int fh_type)
 214 {
 215         if (fh_type == 1)
 216                 return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw,
 217                                                                 fh_len);
 218         else
 219                 return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw,
 220                                                                 fh_len);
 221 }
 222
 223 /*
 224  * get parent, if possible.
 225  *
 226  * FIXME: we could do better by querying the mds to discover the
 227  * parent.
 228  */
 229 static struct dentry *ceph_fh_to_parent(struct super_block *sb,
 230                                          struct fid *fid,
 231                                         int fh_len, int fh_type)
 232 {
 233         struct ceph_nfs_confh *cfh = (void *)fid->raw;
 234         struct ceph_vino vino;
 235         struct inode *inode;
 236         struct dentry *dentry;
 237         int err;
 238
 239         if (fh_type == 1)
 240                 return ERR_PTR(-ESTALE);
 241         if (fh_len < sizeof(*cfh) / 4)
 242                 return ERR_PTR(-ESTALE);
 243
 244         pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
 245                  cfh->parent_name_hash);
 246
 247         vino.ino = cfh->ino;
 248         vino.snap = CEPH_NOSNAP;
 249         inode = ceph_find_inode(sb, vino);
 250         if (!inode)
 251                 return ERR_PTR(-ESTALE);
 252
 253         dentry = d_obtain_alias(inode);
 254         if (IS_ERR(dentry)) {
 255                 pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
 256                        cfh->ino, inode);
 257                 iput(inode);
 258                 return dentry;
 259         }
 260         err = ceph_init_dentry(dentry);
 261         if (err < 0) {
 262                 iput(inode);
 263                 return ERR_PTR(err);
 264         }
 265         dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
 266         return dentry;
 267 }
 268
 269 const struct export_operations ceph_export_ops = {
 270         .encode_fh = ceph_encode_fh,
 271         .fh_to_dentry = ceph_fh_to_dentry,
 272         .fh_to_parent = ceph_fh_to_parent,
 273 };