fs/9p/fid.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * V9FS FID Management
   4  *
   5  *  Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
   6  *  Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/errno.h>
  11 #include <linux/fs.h>
  12 #include <linux/slab.h>
  13 #include <linux/sched.h>
  14 #include <linux/idr.h>
  15 #include <net/9p/9p.h>
  16 #include <net/9p/client.h>
  17
  18 #include "v9fs.h"
  19 #include "v9fs_vfs.h"
  20 #include "fid.h"
  21
  22 /**
  23  * v9fs_fid_add - add a fid to a dentry
  24  * @dentry: dentry that the fid is being added to
  25  * @fid: fid to add
  26  *
  27  */
  28
  29 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
  30 {
  31         hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
  32 }
  33
  34 void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
  35 {
  36         spin_lock(&dentry->d_lock);
  37         __add_fid(dentry, fid);
  38         spin_unlock(&dentry->d_lock);
  39 }
  40
  41 /**
  42  * v9fs_fid_find_inode - search for an open fid off of the inode list
  43  * @inode: return a fid pointing to a specific inode
  44  * @uid: return a fid belonging to the specified user
  45  *
  46  */
  47
  48 static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid)
  49 {
  50         struct hlist_head *h;
  51         struct p9_fid *fid, *ret = NULL;
  52
  53         p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode);
  54
  55         spin_lock(&inode->i_lock);
  56         h = (struct hlist_head *)&inode->i_private;
  57         hlist_for_each_entry(fid, h, ilist) {
  58                 if (uid_eq(fid->uid, uid)) {
  59                         refcount_inc(&fid->count);
  60                         ret = fid;
  61                         break;
  62                 }
  63         }
  64         spin_unlock(&inode->i_lock);
  65         return ret;
  66 }
  67
  68 /**
  69  * v9fs_open_fid_add - add an open fid to an inode
  70  * @dentry: inode that the fid is being added to
  71  * @fid: fid to add
  72  *
  73  */
  74
  75 void v9fs_open_fid_add(struct inode *inode, struct p9_fid *fid)
  76 {
  77         spin_lock(&inode->i_lock);
  78         hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
  79         spin_unlock(&inode->i_lock);
  80 }
  81
  82
  83 /**
  84  * v9fs_fid_find - retrieve a fid that belongs to the specified uid
  85  * @dentry: dentry to look for fid in
  86  * @uid: return fid that belongs to the specified user
  87  * @any: if non-zero, return any fid associated with the dentry
  88  *
  89  */
  90
  91 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
  92 {
  93         struct p9_fid *fid, *ret;
  94
  95         p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",
  96                  dentry, dentry, from_kuid(&init_user_ns, uid),
  97                  any);
  98         ret = NULL;
  99
 100         if (d_inode(dentry))
 101                 ret = v9fs_fid_find_inode(d_inode(dentry), uid);
 102
 103         /* we'll recheck under lock if there's anything to look in */
 104         if (!ret && dentry->d_fsdata) {
 105                 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
 106                 spin_lock(&dentry->d_lock);
 107                 hlist_for_each_entry(fid, h, dlist) {
 108                         if (any || uid_eq(fid->uid, uid)) {
 109                                 ret = fid;
 110                                 refcount_inc(&ret->count);
 111                                 break;
 112                         }
 113                 }
 114                 spin_unlock(&dentry->d_lock);
 115         }
 116
 117         return ret;
 118 }
 119
 120 /*
 121  * We need to hold v9ses->rename_sem as long as we hold references
 122  * to returned path array. Array element contain pointers to
 123  * dentry names.
 124  */
 125 static int build_path_from_dentry(struct v9fs_session_info *v9ses,
 126                                   struct dentry *dentry, const unsigned char ***names)
 127 {
 128         int n = 0, i;
 129         const unsigned char **wnames;
 130         struct dentry *ds;
 131
 132         for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
 133                 n++;
 134
 135         wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
 136         if (!wnames)
 137                 goto err_out;
 138
 139         for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
 140                 wnames[i] = ds->d_name.name;
 141
 142         *names = wnames;
 143         return n;
 144 err_out:
 145         return -ENOMEM;
 146 }
 147
 148 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
 149                                                kuid_t uid, int any)
 150 {
 151         struct dentry *ds;
 152         const unsigned char **wnames, *uname;
 153         int i, n, l, clone, access;
 154         struct v9fs_session_info *v9ses;
 155         struct p9_fid *fid, *old_fid = NULL;
 156
 157         v9ses = v9fs_dentry2v9ses(dentry);
 158         access = v9ses->flags & V9FS_ACCESS_MASK;
 159         fid = v9fs_fid_find(dentry, uid, any);
 160         if (fid)
 161                 return fid;
 162         /*
 163          * we don't have a matching fid. To do a TWALK we need
 164          * parent fid. We need to prevent rename when we want to
 165          * look at the parent.
 166          */
 167         down_read(&v9ses->rename_sem);
 168         ds = dentry->d_parent;
 169         fid = v9fs_fid_find(ds, uid, any);
 170         if (fid) {
 171                 /* Found the parent fid do a lookup with that */
 172                 struct p9_fid *ofid = fid;
 173
 174                 fid = p9_client_walk(ofid, 1, &dentry->d_name.name, 1);
 175                 p9_client_clunk(ofid);
 176                 goto fid_out;
 177         }
 178         up_read(&v9ses->rename_sem);
 179
 180         /* start from the root and try to do a lookup */
 181         fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
 182         if (!fid) {
 183                 /* the user is not attached to the fs yet */
 184                 if (access == V9FS_ACCESS_SINGLE)
 185                         return ERR_PTR(-EPERM);
 186
 187                 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
 188                                 uname = NULL;
 189                 else
 190                         uname = v9ses->uname;
 191
 192                 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
 193                                        v9ses->aname);
 194                 if (IS_ERR(fid))
 195                         return fid;
 196
 197                 v9fs_fid_add(dentry->d_sb->s_root, fid);
 198         }
 199         /* If we are root ourself just return that */
 200         if (dentry->d_sb->s_root == dentry) {
 201                 refcount_inc(&fid->count);
 202                 return fid;
 203         }
 204         /*
 205          * Do a multipath walk with attached root.
 206          * When walking parent we need to make sure we
 207          * don't have a parallel rename happening
 208          */
 209         down_read(&v9ses->rename_sem);
 210         n  = build_path_from_dentry(v9ses, dentry, &wnames);
 211         if (n < 0) {
 212                 fid = ERR_PTR(n);
 213                 goto err_out;
 214         }
 215         clone = 1;
 216         i = 0;
 217         while (i < n) {
 218                 l = min(n - i, P9_MAXWELEM);
 219                 /*
 220                  * We need to hold rename lock when doing a multipath
 221                  * walk to ensure none of the patch component change
 222                  */
 223                 fid = p9_client_walk(fid, l, &wnames[i], clone);
 224                 if (IS_ERR(fid)) {
 225                         if (old_fid) {
 226                                 /*
 227                                  * If we fail, clunk fid which are mapping
 228                                  * to path component and not the last component
 229                                  * of the path.
 230                                  */
 231                                 p9_client_clunk(old_fid);
 232                         }
 233                         kfree(wnames);
 234                         goto err_out;
 235                 }
 236                 old_fid = fid;
 237                 i += l;
 238                 clone = 0;
 239         }
 240         kfree(wnames);
 241 fid_out:
 242         if (!IS_ERR(fid)) {
 243                 spin_lock(&dentry->d_lock);
 244                 if (d_unhashed(dentry)) {
 245                         spin_unlock(&dentry->d_lock);
 246                         p9_client_clunk(fid);
 247                         fid = ERR_PTR(-ENOENT);
 248                 } else {
 249                         __add_fid(dentry, fid);
 250                         refcount_inc(&fid->count);
 251                         spin_unlock(&dentry->d_lock);
 252                 }
 253         }
 254 err_out:
 255         up_read(&v9ses->rename_sem);
 256         return fid;
 257 }
 258
 259 /**
 260  * v9fs_fid_lookup - lookup for a fid, try to walk if not found
 261  * @dentry: dentry to look for fid in
 262  *
 263  * Look for a fid in the specified dentry for the current user.
 264  * If no fid is found, try to create one walking from a fid from the parent
 265  * dentry (if it has one), or the root dentry. If the user haven't accessed
 266  * the fs yet, attach now and walk from the root.
 267  */
 268
 269 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 270 {
 271         kuid_t uid;
 272         int  any, access;
 273         struct v9fs_session_info *v9ses;
 274
 275         v9ses = v9fs_dentry2v9ses(dentry);
 276         access = v9ses->flags & V9FS_ACCESS_MASK;
 277         switch (access) {
 278         case V9FS_ACCESS_SINGLE:
 279         case V9FS_ACCESS_USER:
 280         case V9FS_ACCESS_CLIENT:
 281                 uid = current_fsuid();
 282                 any = 0;
 283                 break;
 284
 285         case V9FS_ACCESS_ANY:
 286                 uid = v9ses->uid;
 287                 any = 1;
 288                 break;
 289
 290         default:
 291                 uid = INVALID_UID;
 292                 any = 0;
 293                 break;
 294         }
 295         return v9fs_fid_lookup_with_uid(dentry, uid, any);
 296 }
 297
 298 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
 299 {
 300         int err;
 301         struct p9_fid *fid, *ofid;
 302
 303         ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0);
 304         fid = clone_fid(ofid);
 305         if (IS_ERR(fid))
 306                 goto error_out;
 307         p9_client_clunk(ofid);
 308         /*
 309          * writeback fid will only be used to write back the
 310          * dirty pages. We always request for the open fid in read-write
 311          * mode so that a partial page write which result in page
 312          * read can work.
 313          */
 314         err = p9_client_open(fid, O_RDWR);
 315         if (err < 0) {
 316                 p9_client_clunk(fid);
 317                 fid = ERR_PTR(err);
 318                 goto error_out;
 319         }
 320 error_out:
 321         return fid;
 322 }