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_debug(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, kuid_t uid, int any)
  78 {
  79         struct v9fs_dentry *dent;
  80         struct p9_fid *fid, *ret;
  81
  82         p9_debug(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n",
  83                  dentry->d_name.name, dentry, from_kuid(&init_user_ns, uid),
  84                  any);
  85         dent = (struct v9fs_dentry *) dentry->d_fsdata;
  86         ret = NULL;
  87         if (dent) {
  88                 spin_lock(&dent->lock);
  89                 list_for_each_entry(fid, &dent->fidlist, dlist) {
  90                         if (any || uid_eq(fid->uid, uid)) {
  91                                 ret = fid;
  92                                 break;
  93                         }
  94                 }
  95                 spin_unlock(&dent->lock);
  96         }
  97
  98         return ret;
  99 }
 100
 101 /*
 102  * We need to hold v9ses->rename_sem as long as we hold references
 103  * to returned path array. Array element contain pointers to
 104  * dentry names.
 105  */
 106 static int build_path_from_dentry(struct v9fs_session_info *v9ses,
 107                                   struct dentry *dentry, char ***names)
 108 {
 109         int n = 0, i;
 110         char **wnames;
 111         struct dentry *ds;
 112
 113         for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
 114                 n++;
 115
 116         wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
 117         if (!wnames)
 118                 goto err_out;
 119
 120         for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
 121                 wnames[i] = (char  *)ds->d_name.name;
 122
 123         *names = wnames;
 124         return n;
 125 err_out:
 126         return -ENOMEM;
 127 }
 128
 129 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
 130                                                kuid_t uid, int any)
 131 {
 132         struct dentry *ds;
 133         char **wnames, *uname;
 134         int i, n, l, clone, access;
 135         struct v9fs_session_info *v9ses;
 136         struct p9_fid *fid, *old_fid = NULL;
 137
 138         v9ses = v9fs_dentry2v9ses(dentry);
 139         access = v9ses->flags & V9FS_ACCESS_MASK;
 140         fid = v9fs_fid_find(dentry, uid, any);
 141         if (fid)
 142                 return fid;
 143         /*
 144          * we don't have a matching fid. To do a TWALK we need
 145          * parent fid. We need to prevent rename when we want to
 146          * look at the parent.
 147          */
 148         down_read(&v9ses->rename_sem);
 149         ds = dentry->d_parent;
 150         fid = v9fs_fid_find(ds, uid, any);
 151         if (fid) {
 152                 /* Found the parent fid do a lookup with that */
 153                 fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1);
 154                 goto fid_out;
 155         }
 156         up_read(&v9ses->rename_sem);
 157
 158         /* start from the root and try to do a lookup */
 159         fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
 160         if (!fid) {
 161                 /* the user is not attached to the fs yet */
 162                 if (access == V9FS_ACCESS_SINGLE)
 163                         return ERR_PTR(-EPERM);
 164
 165                 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
 166                                 uname = NULL;
 167                 else
 168                         uname = v9ses->uname;
 169
 170                 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
 171                                        v9ses->aname);
 172                 if (IS_ERR(fid))
 173                         return fid;
 174
 175                 v9fs_fid_add(dentry->d_sb->s_root, fid);
 176         }
 177         /* If we are root ourself just return that */
 178         if (dentry->d_sb->s_root == dentry)
 179                 return fid;
 180         /*
 181          * Do a multipath walk with attached root.
 182          * When walking parent we need to make sure we
 183          * don't have a parallel rename happening
 184          */
 185         down_read(&v9ses->rename_sem);
 186         n  = build_path_from_dentry(v9ses, dentry, &wnames);
 187         if (n < 0) {
 188                 fid = ERR_PTR(n);
 189                 goto err_out;
 190         }
 191         clone = 1;
 192         i = 0;
 193         while (i < n) {
 194                 l = min(n - i, P9_MAXWELEM);
 195                 /*
 196                  * We need to hold rename lock when doing a multipath
 197                  * walk to ensure none of the patch component change
 198                  */
 199                 fid = p9_client_walk(fid, l, &wnames[i], clone);
 200                 if (IS_ERR(fid)) {
 201                         if (old_fid) {
 202                                 /*
 203                                  * If we fail, clunk fid which are mapping
 204                                  * to path component and not the last component
 205                                  * of the path.
 206                                  */
 207                                 p9_client_clunk(old_fid);
 208                         }
 209                         kfree(wnames);
 210                         goto err_out;
 211                 }
 212                 old_fid = fid;
 213                 i += l;
 214                 clone = 0;
 215         }
 216         kfree(wnames);
 217 fid_out:
 218         if (!IS_ERR(fid))
 219                 v9fs_fid_add(dentry, fid);
 220 err_out:
 221         up_read(&v9ses->rename_sem);
 222         return fid;
 223 }
 224
 225 /**
 226  * v9fs_fid_lookup - lookup for a fid, try to walk if not found
 227  * @dentry: dentry to look for fid in
 228  *
 229  * Look for a fid in the specified dentry for the current user.
 230  * If no fid is found, try to create one walking from a fid from the parent
 231  * dentry (if it has one), or the root dentry. If the user haven't accessed
 232  * the fs yet, attach now and walk from the root.
 233  */
 234
 235 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 236 {
 237         kuid_t uid;
 238         int  any, access;
 239         struct v9fs_session_info *v9ses;
 240
 241         v9ses = v9fs_dentry2v9ses(dentry);
 242         access = v9ses->flags & V9FS_ACCESS_MASK;
 243         switch (access) {
 244         case V9FS_ACCESS_SINGLE:
 245         case V9FS_ACCESS_USER:
 246         case V9FS_ACCESS_CLIENT:
 247                 uid = current_fsuid();
 248                 any = 0;
 249                 break;
 250
 251         case V9FS_ACCESS_ANY:
 252                 uid = v9ses->uid;
 253                 any = 1;
 254                 break;
 255
 256         default:
 257                 uid = INVALID_UID;
 258                 any = 0;
 259                 break;
 260         }
 261         return v9fs_fid_lookup_with_uid(dentry, uid, any);
 262 }
 263
 264 struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
 265 {
 266         struct p9_fid *fid, *ret;
 267
 268         fid = v9fs_fid_lookup(dentry);
 269         if (IS_ERR(fid))
 270                 return fid;
 271
 272         ret = p9_client_walk(fid, 0, NULL, 1);
 273         return ret;
 274 }
 275
 276 static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, kuid_t uid)
 277 {
 278         struct p9_fid *fid, *ret;
 279
 280         fid = v9fs_fid_lookup_with_uid(dentry, uid, 0);
 281         if (IS_ERR(fid))
 282                 return fid;
 283
 284         ret = p9_client_walk(fid, 0, NULL, 1);
 285         return ret;
 286 }
 287
 288 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
 289 {
 290         int err;
 291         struct p9_fid *fid;
 292
 293         fid = v9fs_fid_clone_with_uid(dentry, GLOBAL_ROOT_UID);
 294         if (IS_ERR(fid))
 295                 goto error_out;
 296         /*
 297          * writeback fid will only be used to write back the
 298          * dirty pages. We always request for the open fid in read-write
 299          * mode so that a partial page write which result in page
 300          * read can work.
 301          */
 302         err = p9_client_open(fid, O_RDWR);
 303         if (err < 0) {
 304                 p9_client_clunk(fid);
 305                 fid = ERR_PTR(err);
 306                 goto error_out;
 307         }
 308 error_out:
 309         return fid;
 310 }