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 = dentry->d_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         if (*max_len >= connected_handle_length) {
  59                 dout("encode_fh %p connectable\n", dentry);
  60                 cfh->ino = ceph_ino(dentry->d_inode);
  61                 cfh->parent_ino = ceph_ino(parent->d_inode);
  62                 cfh->parent_name_hash = ceph_dentry_hash(parent);
  63                 *max_len = connected_handle_length;
  64                 type = 2;
  65         } else if (*max_len >= handle_length) {
  66                 if (connectable) {
  67                         *max_len = connected_handle_length;
  68                         return 255;
  69                 }
  70                 dout("encode_fh %p\n", dentry);
  71                 fh->ino = ceph_ino(dentry->d_inode);
  72                 *max_len = handle_length;
  73                 type = 1;
  74         } else {
  75                 *max_len = handle_length;
  76                 return 255;
  77         }
  78         return type;
  79 }
  80
  81 /*
  82  * convert regular fh to dentry
  83  *
  84  * FIXME: we should try harder by querying the mds for the ino.
  85  */
  86 static struct dentry *__fh_to_dentry(struct super_block *sb,
  87                                      struct ceph_nfs_fh *fh)
  88 {
  89         struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
  90         struct inode *inode;
  91         struct dentry *dentry;
  92         struct ceph_vino vino;
  93         int err;
  94
  95         dout("__fh_to_dentry %llx\n", fh->ino);
  96         vino.ino = fh->ino;
  97         vino.snap = CEPH_NOSNAP;
  98         inode = ceph_find_inode(sb, vino);
  99         if (!inode) {
 100                 struct ceph_mds_request *req;
 101
 102                 req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPINO,
 103                                                USE_ANY_MDS);
 104                 if (IS_ERR(req))
 105                         return ERR_CAST(req);
 106
 107                 req->r_ino1 = vino;
 108                 req->r_num_caps = 1;
 109                 err = ceph_mdsc_do_request(mdsc, NULL, req);
 110                 inode = req->r_target_inode;
 111                 if (inode)
 112                         igrab(inode);
 113                 ceph_mdsc_put_request(req);
 114                 if (!inode)
 115                         return ERR_PTR(-ESTALE);
 116         }
 117
 118         dentry = d_obtain_alias(inode);
 119         if (IS_ERR(dentry)) {
 120                 pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
 121                        fh->ino, inode);
 122                 iput(inode);
 123                 return dentry;
 124         }
 125         err = ceph_init_dentry(dentry);
 126
 127         if (err < 0) {
 128                 iput(inode);
 129                 return ERR_PTR(err);
 130         }
 131         dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
 132         return dentry;
 133 }
 134
 135 /*
 136  * convert connectable fh to dentry
 137  */
 138 static struct dentry *__cfh_to_dentry(struct super_block *sb,
 139                                       struct ceph_nfs_confh *cfh)
 140 {
 141         struct ceph_mds_client *mdsc = ceph_sb_to_client(sb)->mdsc;
 142         struct inode *inode;
 143         struct dentry *dentry;
 144         struct ceph_vino vino;
 145         int err;
 146
 147         dout("__cfh_to_dentry %llx (%llx/%x)\n",
 148              cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
 149
 150         vino.ino = cfh->ino;
 151         vino.snap = CEPH_NOSNAP;
 152         inode = ceph_find_inode(sb, vino);
 153         if (!inode) {
 154                 struct ceph_mds_request *req;
 155
 156                 req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
 157                                                USE_ANY_MDS);
 158                 if (IS_ERR(req))
 159                         return ERR_CAST(req);
 160
 161                 req->r_ino1 = vino;
 162                 req->r_ino2.ino = cfh->parent_ino;
 163                 req->r_ino2.snap = CEPH_NOSNAP;
 164                 req->r_path2 = kmalloc(16, GFP_NOFS);
 165                 snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
 166                 req->r_num_caps = 1;
 167                 err = ceph_mdsc_do_request(mdsc, NULL, req);
 168                 inode = req->r_target_inode;
 169                 if (inode)
 170                         igrab(inode);
 171                 ceph_mdsc_put_request(req);
 172                 if (!inode)
 173                         return ERR_PTR(err ? err : -ESTALE);
 174         }
 175
 176         dentry = d_obtain_alias(inode);
 177         if (IS_ERR(dentry)) {
 178                 pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
 179                        cfh->ino, inode);
 180                 iput(inode);
 181                 return dentry;
 182         }
 183         err = ceph_init_dentry(dentry);
 184         if (err < 0) {
 185                 iput(inode);
 186                 return ERR_PTR(err);
 187         }
 188         dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
 189         return dentry;
 190 }
 191
 192 static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
 193                                         int fh_len, int fh_type)
 194 {
 195         if (fh_type == 1)
 196                 return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw);
 197         else
 198                 return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw);
 199 }
 200
 201 /*
 202  * get parent, if possible.
 203  *
 204  * FIXME: we could do better by querying the mds to discover the
 205  * parent.
 206  */
 207 static struct dentry *ceph_fh_to_parent(struct super_block *sb,
 208                                          struct fid *fid,
 209                                         int fh_len, int fh_type)
 210 {
 211         struct ceph_nfs_confh *cfh = (void *)fid->raw;
 212         struct ceph_vino vino;
 213         struct inode *inode;
 214         struct dentry *dentry;
 215         int err;
 216
 217         if (fh_type == 1)
 218                 return ERR_PTR(-ESTALE);
 219
 220         pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
 221                  cfh->parent_name_hash);
 222
 223         vino.ino = cfh->ino;
 224         vino.snap = CEPH_NOSNAP;
 225         inode = ceph_find_inode(sb, vino);
 226         if (!inode)
 227                 return ERR_PTR(-ESTALE);
 228
 229         dentry = d_obtain_alias(inode);
 230         if (IS_ERR(dentry)) {
 231                 pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
 232                        cfh->ino, inode);
 233                 iput(inode);
 234                 return dentry;
 235         }
 236         err = ceph_init_dentry(dentry);
 237         if (err < 0) {
 238                 iput(inode);
 239                 return ERR_PTR(err);
 240         }
 241         dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
 242         return dentry;
 243 }
 244
 245 const struct export_operations ceph_export_ops = {
 246         .encode_fh = ceph_encode_fh,
 247         .fh_to_dentry = ceph_fh_to_dentry,
 248         .fh_to_parent = ceph_fh_to_parent,
 249 };