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         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  */
 103 static 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  */
 157 static 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
 214 static 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  */
 231 static 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
 271 const 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 };