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  * v9fs_fid_lookup - lookup for a fid, try to walk if not found
 102  * @dentry: dentry to look for fid in
 103  *
 104  * Look for a fid in the specified dentry for the current user.
 105  * If no fid is found, try to create one walking from a fid from the parent
 106  * dentry (if it has one), or the root dentry. If the user haven't accessed
 107  * the fs yet, attach now and walk from the root.
 108  */
 109
 110 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 111 {
 112         int i, n, l, clone, any, access;
 113         u32 uid;
 114         struct p9_fid *fid, *old_fid = NULL;
 115         struct dentry *d, *ds;
 116         struct v9fs_session_info *v9ses;
 117         char **wnames, *uname;
 118
 119         v9ses = v9fs_inode2v9ses(dentry->d_inode);
 120         access = v9ses->flags & V9FS_ACCESS_MASK;
 121         switch (access) {
 122         case V9FS_ACCESS_SINGLE:
 123         case V9FS_ACCESS_USER:
 124                 uid = current_fsuid();
 125                 any = 0;
 126                 break;
 127
 128         case V9FS_ACCESS_ANY:
 129                 uid = v9ses->uid;
 130                 any = 1;
 131                 break;
 132
 133         default:
 134                 uid = ~0;
 135                 any = 0;
 136                 break;
 137         }
 138
 139         fid = v9fs_fid_find(dentry, uid, any);
 140         if (fid)
 141                 return fid;
 142
 143         ds = dentry->d_parent;
 144         fid = v9fs_fid_find(ds, uid, any);
 145         if (!fid) { /* walk from the root */
 146                 n = 0;
 147                 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
 148                         n++;
 149
 150                 fid = v9fs_fid_find(ds, uid, any);
 151                 if (!fid) { /* the user is not attached to the fs yet */
 152                         if (access == V9FS_ACCESS_SINGLE)
 153                                 return ERR_PTR(-EPERM);
 154
 155                         if (v9fs_proto_dotu(v9ses))
 156                                 uname = NULL;
 157                         else
 158                                 uname = v9ses->uname;
 159
 160                         fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
 161                                 v9ses->aname);
 162
 163                         if (IS_ERR(fid))
 164                                 return fid;
 165
 166                         v9fs_fid_add(ds, fid);
 167                 }
 168         } else /* walk from the parent */
 169                 n = 1;
 170
 171         if (ds == dentry)
 172                 return fid;
 173
 174         wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
 175         if (!wnames)
 176                 return ERR_PTR(-ENOMEM);
 177
 178         for (d = dentry, i = (n-1); i >= 0; i--, d = d->d_parent)
 179                 wnames[i] = (char *) d->d_name.name;
 180
 181         clone = 1;
 182         i = 0;
 183         while (i < n) {
 184                 l = min(n - i, P9_MAXWELEM);
 185                 fid = p9_client_walk(fid, l, &wnames[i], clone);
 186                 if (IS_ERR(fid)) {
 187                         if (old_fid) {
 188                                 /*
 189                                  * If we fail, clunk fid which are mapping
 190                                  * to path component and not the last component
 191                                  * of the path.
 192                                  */
 193                                 p9_client_clunk(old_fid);
 194                         }
 195                         kfree(wnames);
 196                         return fid;
 197                 }
 198                 old_fid = fid;
 199                 i += l;
 200                 clone = 0;
 201         }
 202
 203         kfree(wnames);
 204         v9fs_fid_add(dentry, fid);
 205         return fid;
 206 }
 207
 208 struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
 209 {
 210         struct p9_fid *fid, *ret;
 211
 212         fid = v9fs_fid_lookup(dentry);
 213         if (IS_ERR(fid))
 214                 return fid;
 215
 216         ret = p9_client_walk(fid, 0, NULL, 1);
 217         return ret;
 218 }