fs/ceph/export.c

   1 #include "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
   9 /*
  10  * NFS export support
  11  *
  12  * NFS re-export of a ceph mount is, at present, only semireliable.
  13  * The basic issue is that the Ceph architectures doesn't lend itself
  14  * well to generating filehandles that will remain valid forever.
  15  *
  16  * So, we do our best.  If you're lucky, your inode will be in the
  17  * client's cache.  If it's not, and you have a connectable fh, then
  18  * the MDS server may be able to find it for you.  Otherwise, you get
  19  * ESTALE.
  20  *
  21  * There are ways to this more reliable, but in the non-connectable fh
  22  * case, we won't every work perfectly, and in the connectable case,
  23  * some changes are needed on the MDS side to work better.
  24  */
  25
  26 /*
  27  * Basic fh
  28  */
  29 struct ceph_nfs_fh {
  30         u64 ino;
  31 } __attribute__ ((packed));
  32
  33 /*
  34  * Larger 'connectable' fh that includes parent ino and name hash.
  35  * Use this whenever possible, as it works more reliably.
  36  */
  37 struct ceph_nfs_confh {
  38         u64 ino, parent_ino;
  39         u32 parent_name_hash;
  40 } __attribute__ ((packed));
  41
  42 static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
  43                           int connectable)
  44 {
  45         struct ceph_nfs_fh *fh = (void *)rawfh;
  46         struct ceph_nfs_confh *cfh = (void *)rawfh;
  47         struct dentry *parent = dentry->d_parent;
  48         struct inode *inode = dentry->d_inode;
  49         int type;
  50
  51         /* don't re-export snaps */
  52         if (ceph_snap(inode) != CEPH_NOSNAP)
  53                 return -EINVAL;
  54
  55         if (*max_len >= sizeof(*cfh)) {
  56                 dout("encode_fh %p connectable\n", dentry);
  57                 cfh->ino = ceph_ino(dentry->d_inode);
  58                 cfh->parent_ino = ceph_ino(parent->d_inode);
  59                 cfh->parent_name_hash = parent->d_name.hash;
  60                 *max_len = sizeof(*cfh);
  61                 type = 2;
  62         } else if (*max_len > sizeof(*fh)) {
  63                 if (connectable)
  64                         return -ENOSPC;
  65                 dout("encode_fh %p\n", dentry);
  66                 fh->ino = ceph_ino(dentry->d_inode);
  67                 *max_len = sizeof(*fh);
  68                 type = 1;
  69         } else {
  70                 return -ENOSPC;
  71         }
  72         return type;
  73 }
  74
  75 /*
  76  * convert regular fh to dentry
  77  *
  78  * FIXME: we should try harder by querying the mds for the ino.
  79  */
  80 static struct dentry *__fh_to_dentry(struct super_block *sb,
  81                                      struct ceph_nfs_fh *fh)
  82 {
  83         struct inode *inode;
  84         struct dentry *dentry;
  85         struct ceph_vino vino;
  86         int err;
  87
  88         dout("__fh_to_dentry %llx\n", fh->ino);
  89         vino.ino = fh->ino;
  90         vino.snap = CEPH_NOSNAP;
  91         inode = ceph_find_inode(sb, vino);
  92         if (!inode)
  93                 return ERR_PTR(-ESTALE);
  94
  95         dentry = d_obtain_alias(inode);
  96         if (IS_ERR(dentry)) {
  97                 pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
  98                        fh->ino, inode);
  99                 iput(inode);
 100                 return dentry;
 101         }
 102         err = ceph_init_dentry(dentry);
 103
 104         if (err < 0) {
 105                 iput(inode);
 106                 return ERR_PTR(err);
 107         }
 108         dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
 109         return dentry;
 110 }
 111
 112 /*
 113  * convert connectable fh to dentry
 114  */
 115 static struct dentry *__cfh_to_dentry(struct super_block *sb,
 116                                       struct ceph_nfs_confh *cfh)
 117 {
 118         struct ceph_mds_client *mdsc = &ceph_sb_to_client(sb)->mdsc;
 119         struct inode *inode;
 120         struct dentry *dentry;
 121         struct ceph_vino vino;
 122         int err;
 123
 124         dout("__cfh_to_dentry %llx (%llx/%x)\n",
 125              cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
 126
 127         vino.ino = cfh->ino;
 128         vino.snap = CEPH_NOSNAP;
 129         inode = ceph_find_inode(sb, vino);
 130         if (!inode) {
 131                 struct ceph_mds_request *req;
 132
 133                 req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
 134                                                USE_ANY_MDS);
 135                 if (IS_ERR(req))
 136                         return ERR_CAST(req);
 137
 138                 req->r_ino1 = vino;
 139                 req->r_ino2.ino = cfh->parent_ino;
 140                 req->r_ino2.snap = CEPH_NOSNAP;
 141                 req->r_path2 = kmalloc(16, GFP_NOFS);
 142                 snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
 143                 req->r_num_caps = 1;
 144                 err = ceph_mdsc_do_request(mdsc, NULL, req);
 145                 ceph_mdsc_put_request(req);
 146                 inode = ceph_find_inode(sb, vino);
 147                 if (!inode)
 148                         return ERR_PTR(err ? err : -ESTALE);
 149         }
 150
 151         dentry = d_obtain_alias(inode);
 152         if (IS_ERR(dentry)) {
 153                 pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
 154                        cfh->ino, inode);
 155                 iput(inode);
 156                 return dentry;
 157         }
 158         err = ceph_init_dentry(dentry);
 159         if (err < 0) {
 160                 iput(inode);
 161                 return ERR_PTR(err);
 162         }
 163         dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
 164         return dentry;
 165 }
 166
 167 static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
 168                                         int fh_len, int fh_type)
 169 {
 170         if (fh_type == 1)
 171                 return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw);
 172         else
 173                 return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw);
 174 }
 175
 176 /*
 177  * get parent, if possible.
 178  *
 179  * FIXME: we could do better by querying the mds to discover the
 180  * parent.
 181  */
 182 static struct dentry *ceph_fh_to_parent(struct super_block *sb,
 183                                          struct fid *fid,
 184                                         int fh_len, int fh_type)
 185 {
 186         struct ceph_nfs_confh *cfh = (void *)fid->raw;
 187         struct ceph_vino vino;
 188         struct inode *inode;
 189         struct dentry *dentry;
 190         int err;
 191
 192         if (fh_type == 1)
 193                 return ERR_PTR(-ESTALE);
 194
 195         pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
 196                  cfh->parent_name_hash);
 197
 198         vino.ino = cfh->ino;
 199         vino.snap = CEPH_NOSNAP;
 200         inode = ceph_find_inode(sb, vino);
 201         if (!inode)
 202                 return ERR_PTR(-ESTALE);
 203
 204         dentry = d_obtain_alias(inode);
 205         if (IS_ERR(dentry)) {
 206                 pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
 207                        cfh->ino, inode);
 208                 iput(inode);
 209                 return dentry;
 210         }
 211         err = ceph_init_dentry(dentry);
 212         if (err < 0) {
 213                 iput(inode);
 214                 return ERR_PTR(err);
 215         }
 216         dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
 217         return dentry;
 218 }
 219
 220 const struct export_operations ceph_export_ops = {
 221         .encode_fh = ceph_encode_fh,
 222         .fh_to_dentry = ceph_fh_to_dentry,
 223         .fh_to_parent = ceph_fh_to_parent,
 224 };