fs/9p/fid.c

   1 /*
   2  * V9FS FID Management
   3  *
   4  *  Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
   5  *  Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License version 2
   9  *  as published by the Free Software Foundation.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, write to:
  18  *  Free Software Foundation
  19  *  51 Franklin Street, Fifth Floor
  20  *  Boston, MA  02111-1301  USA
  21  *
  22  */
  23
  24 #include <linux/module.h>
  25 #include <linux/errno.h>
  26 #include <linux/fs.h>
  27 #include <linux/slab.h>
  28 #include <linux/sched.h>
  29 #include <linux/idr.h>
  30 #include <net/9p/9p.h>
  31 #include <net/9p/client.h>
  32
  33 #include "v9fs.h"
  34 #include "v9fs_vfs.h"
  35 #include "fid.h"
  36
  37 /**
  38  * v9fs_fid_add - add a fid to a dentry
  39  * @dentry: dentry that the fid is being added to
  40  * @fid: fid to add
  41  *
  42  */
  43
  44 int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
  45 {
  46         struct v9fs_dentry *dent;
  47
  48         P9_DPRINTK(P9_DEBUG_VFS, "fid %d dentry %s\n",
  49                                         fid->fid, dentry->d_name.name);
  50
  51         dent = dentry->d_fsdata;
  52         if (!dent) {
  53                 dent = kmalloc(sizeof(struct v9fs_dentry), GFP_KERNEL);
  54                 if (!dent)
  55                         return -ENOMEM;
  56
  57                 spin_lock_init(&dent->lock);
  58                 INIT_LIST_HEAD(&dent->fidlist);
  59                 dentry->d_fsdata = dent;
  60         }
  61
  62         spin_lock(&dent->lock);
  63         list_add(&fid->dlist, &dent->fidlist);
  64         spin_unlock(&dent->lock);
  65
  66         return 0;
  67 }
  68
  69 /**
  70  * v9fs_fid_find - retrieve a fid that belongs to the specified uid
  71  * @dentry: dentry to look for fid in
  72  * @uid: return fid that belongs to the specified user
  73  * @any: if non-zero, return any fid associated with the dentry
  74  *
  75  */
  76
  77 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any)
  78 {
  79         struct v9fs_dentry *dent;
  80         struct p9_fid *fid, *ret;
  81
  82         P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n",
  83                 dentry->d_name.name, dentry, uid, any);
  84         dent = (struct v9fs_dentry *) dentry->d_fsdata;
  85         ret = NULL;
  86         if (dent) {
  87                 spin_lock(&dent->lock);
  88                 list_for_each_entry(fid, &dent->fidlist, dlist) {
  89                         if (any || fid->uid == uid) {
  90                                 ret = fid;
  91                                 break;
  92                         }
  93                 }
  94                 spin_unlock(&dent->lock);
  95         }
  96
  97         return ret;
  98 }
  99
 100 /*
 101  * We need to hold v9ses->rename_sem as long as we hold references
 102  * to returned path array. Array element contain pointers to
 103  * dentry names.
 104  */
 105 static int build_path_from_dentry(struct v9fs_session_info *v9ses,
 106                                   struct dentry *dentry, char ***names)
 107 {
 108         int n = 0, i;
 109         char **wnames;
 110         struct dentry *ds;
 111
 112         for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
 113                 n++;
 114
 115         wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
 116         if (!wnames)
 117                 goto err_out;
 118
 119         for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
 120                 wnames[i] = (char  *)ds->d_name.name;
 121
 122         *names = wnames;
 123         return n;
 124 err_out:
 125         return -ENOMEM;
 126 }
 127
 128 /**
 129  * v9fs_fid_lookup - lookup for a fid, try to walk if not found
 130  * @dentry: dentry to look for fid in
 131  *
 132  * Look for a fid in the specified dentry for the current user.
 133  * If no fid is found, try to create one walking from a fid from the parent
 134  * dentry (if it has one), or the root dentry. If the user haven't accessed
 135  * the fs yet, attach now and walk from the root.
 136  */
 137
 138 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 139 {
 140         int i, n, l, clone, any, access;
 141         u32 uid;
 142         struct p9_fid *fid, *old_fid = NULL;
 143         struct dentry *ds;
 144         struct v9fs_session_info *v9ses;
 145         char **wnames, *uname;
 146
 147         v9ses = v9fs_inode2v9ses(dentry->d_inode);
 148         access = v9ses->flags & V9FS_ACCESS_MASK;
 149         switch (access) {
 150         case V9FS_ACCESS_SINGLE:
 151         case V9FS_ACCESS_USER:
 152                 uid = current_fsuid();
 153                 any = 0;
 154                 break;
 155
 156         case V9FS_ACCESS_ANY:
 157                 uid = v9ses->uid;
 158                 any = 1;
 159                 break;
 160
 161         default:
 162                 uid = ~0;
 163                 any = 0;
 164                 break;
 165         }
 166
 167         fid = v9fs_fid_find(dentry, uid, any);
 168         if (fid)
 169                 return fid;
 170         /*
 171          * we don't have a matching fid. To do a TWALK we need
 172          * parent fid. We need to prevent rename when we want to
 173          * look at the parent.
 174          */
 175         down_read(&v9ses->rename_sem);
 176         ds = dentry->d_parent;
 177         fid = v9fs_fid_find(ds, uid, any);
 178         if (fid) {
 179                 /* Found the parent fid do a lookup with that */
 180                 fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1);
 181                 goto fid_out;
 182         }
 183         up_read(&v9ses->rename_sem);
 184
 185         /* start from the root and try to do a lookup */
 186         fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
 187         if (!fid) {
 188                 /* the user is not attached to the fs yet */
 189                 if (access == V9FS_ACCESS_SINGLE)
 190                         return ERR_PTR(-EPERM);
 191
 192                 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
 193                                 uname = NULL;
 194                 else
 195                         uname = v9ses->uname;
 196
 197                 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
 198                                        v9ses->aname);
 199                 if (IS_ERR(fid))
 200                         return fid;
 201
 202                 v9fs_fid_add(dentry->d_sb->s_root, fid);
 203         }
 204         /* If we are root ourself just return that */
 205         if (dentry->d_sb->s_root == dentry)
 206                 return fid;
 207         /*
 208          * Do a multipath walk with attached root.
 209          * When walking parent we need to make sure we
 210          * don't have a parallel rename happening
 211          */
 212         down_read(&v9ses->rename_sem);
 213         n  = build_path_from_dentry(v9ses, dentry, &wnames);
 214         if (n < 0) {
 215                 fid = ERR_PTR(n);
 216                 goto err_out;
 217         }
 218         clone = 1;
 219         i = 0;
 220         while (i < n) {
 221                 l = min(n - i, P9_MAXWELEM);
 222                 /*
 223                  * We need to hold rename lock when doing a multipath
 224                  * walk to ensure none of the patch component change
 225                  */
 226                 fid = p9_client_walk(fid, l, &wnames[i], clone);
 227                 if (IS_ERR(fid)) {
 228                         if (old_fid) {
 229                                 /*
 230                                  * If we fail, clunk fid which are mapping
 231                                  * to path component and not the last component
 232                                  * of the path.
 233                                  */
 234                                 p9_client_clunk(old_fid);
 235                         }
 236                         kfree(wnames);
 237                         goto err_out;
 238                 }
 239                 old_fid = fid;
 240                 i += l;
 241                 clone = 0;
 242         }
 243         kfree(wnames);
 244 fid_out:
 245         if (!IS_ERR(fid))
 246                 v9fs_fid_add(dentry, fid);
 247 err_out:
 248         up_read(&v9ses->rename_sem);
 249         return fid;
 250 }
 251
 252 struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
 253 {
 254         struct p9_fid *fid, *ret;
 255
 256         fid = v9fs_fid_lookup(dentry);
 257         if (IS_ERR(fid))
 258                 return fid;
 259
 260         ret = p9_client_walk(fid, 0, NULL, 1);
 261         return ret;
 262 }