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 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
  23 {
  24         hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
  25 }
  26
  27
  28 /**
  29  * v9fs_fid_add - add a fid to a dentry
  30  * @dentry: dentry that the fid is being added to
  31  * @pfid: fid to add, NULLed out
  32  *
  33  */
  34 void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid)
  35 {
  36         struct p9_fid *fid = *pfid;
  37
  38         spin_lock(&dentry->d_lock);
  39         __add_fid(dentry, fid);
  40         spin_unlock(&dentry->d_lock);
  41
  42         *pfid = NULL;
  43 }
  44
  45 /**
  46  * v9fs_fid_find_inode - search for an open fid off of the inode list
  47  * @inode: return a fid pointing to a specific inode
  48  * @uid: return a fid belonging to the specified user
  49  *
  50  */
  51
  52 static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid)
  53 {
  54         struct hlist_head *h;
  55         struct p9_fid *fid, *ret = NULL;
  56
  57         p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode);
  58
  59         spin_lock(&inode->i_lock);
  60         h = (struct hlist_head *)&inode->i_private;
  61         hlist_for_each_entry(fid, h, ilist) {
  62                 if (uid_eq(fid->uid, uid)) {
  63                         p9_fid_get(fid);
  64                         ret = fid;
  65                         break;
  66                 }
  67         }
  68         spin_unlock(&inode->i_lock);
  69         return ret;
  70 }
  71
  72 /**
  73  * v9fs_open_fid_add - add an open fid to an inode
  74  * @inode: inode that the fid is being added to
  75  * @pfid: fid to add, NULLed out
  76  *
  77  */
  78
  79 void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
  80 {
  81         struct p9_fid *fid = *pfid;
  82
  83         spin_lock(&inode->i_lock);
  84         hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
  85         spin_unlock(&inode->i_lock);
  86
  87         *pfid = NULL;
  88 }
  89
  90
  91 /**
  92  * v9fs_fid_find - retrieve a fid that belongs to the specified uid
  93  * @dentry: dentry to look for fid in
  94  * @uid: return fid that belongs to the specified user
  95  * @any: if non-zero, return any fid associated with the dentry
  96  *
  97  */
  98
  99 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
 100 {
 101         struct p9_fid *fid, *ret;
 102
 103         p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",
 104                  dentry, dentry, from_kuid(&init_user_ns, uid),
 105                  any);
 106         ret = NULL;
 107         /* we'll recheck under lock if there's anything to look in */
 108         if (dentry->d_fsdata) {
 109                 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
 110
 111                 spin_lock(&dentry->d_lock);
 112                 hlist_for_each_entry(fid, h, dlist) {
 113                         if (any || uid_eq(fid->uid, uid)) {
 114                                 ret = fid;
 115                                 p9_fid_get(ret);
 116                                 break;
 117                         }
 118                 }
 119                 spin_unlock(&dentry->d_lock);
 120         } else {
 121                 if (dentry->d_inode)
 122                         ret = v9fs_fid_find_inode(dentry->d_inode, uid);
 123         }
 124
 125         return ret;
 126 }
 127
 128 /*
 129  * We need to hold v9ses->rename_sem as long as we hold references
 130  * to returned path array. Array element contain pointers to
 131  * dentry names.
 132  */
 133 static int build_path_from_dentry(struct v9fs_session_info *v9ses,
 134                                   struct dentry *dentry, const unsigned char ***names)
 135 {
 136         int n = 0, i;
 137         const unsigned char **wnames;
 138         struct dentry *ds;
 139
 140         for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
 141                 n++;
 142
 143         wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
 144         if (!wnames)
 145                 goto err_out;
 146
 147         for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
 148                 wnames[i] = ds->d_name.name;
 149
 150         *names = wnames;
 151         return n;
 152 err_out:
 153         return -ENOMEM;
 154 }
 155
 156 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
 157                                                kuid_t uid, int any)
 158 {
 159         struct dentry *ds;
 160         const unsigned char **wnames, *uname;
 161         int i, n, l, access;
 162         struct v9fs_session_info *v9ses;
 163         struct p9_fid *fid, *root_fid, *old_fid;
 164
 165         v9ses = v9fs_dentry2v9ses(dentry);
 166         access = v9ses->flags & V9FS_ACCESS_MASK;
 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                 old_fid = fid;
 181
 182                 fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1);
 183                 p9_fid_put(old_fid);
 184                 goto fid_out;
 185         }
 186         up_read(&v9ses->rename_sem);
 187
 188         /* start from the root and try to do a lookup */
 189         root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
 190         if (!root_fid) {
 191                 /* the user is not attached to the fs yet */
 192                 if (access == V9FS_ACCESS_SINGLE)
 193                         return ERR_PTR(-EPERM);
 194
 195                 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
 196                         uname = NULL;
 197                 else
 198                         uname = v9ses->uname;
 199
 200                 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
 201                                        v9ses->aname);
 202                 if (IS_ERR(fid))
 203                         return fid;
 204
 205                 root_fid = p9_fid_get(fid);
 206                 v9fs_fid_add(dentry->d_sb->s_root, &fid);
 207         }
 208         /* If we are root ourself just return that */
 209         if (dentry->d_sb->s_root == dentry)
 210                 return root_fid;
 211
 212         /*
 213          * Do a multipath walk with attached root.
 214          * When walking parent we need to make sure we
 215          * don't have a parallel rename happening
 216          */
 217         down_read(&v9ses->rename_sem);
 218         n  = build_path_from_dentry(v9ses, dentry, &wnames);
 219         if (n < 0) {
 220                 fid = ERR_PTR(n);
 221                 goto err_out;
 222         }
 223         fid = root_fid;
 224         old_fid = root_fid;
 225         i = 0;
 226         while (i < n) {
 227                 l = min(n - i, P9_MAXWELEM);
 228                 /*
 229                  * We need to hold rename lock when doing a multipath
 230                  * walk to ensure none of the path components change
 231                  */
 232                 fid = p9_client_walk(old_fid, l, &wnames[i],
 233                                      old_fid == root_fid /* clone */);
 234                 /* non-cloning walk will return the same fid */
 235                 if (fid != old_fid) {
 236                         p9_fid_put(old_fid);
 237                         old_fid = fid;
 238                 }
 239                 if (IS_ERR(fid)) {
 240                         kfree(wnames);
 241                         goto err_out;
 242                 }
 243                 i += l;
 244         }
 245         kfree(wnames);
 246 fid_out:
 247         if (!IS_ERR(fid)) {
 248                 spin_lock(&dentry->d_lock);
 249                 if (d_unhashed(dentry)) {
 250                         spin_unlock(&dentry->d_lock);
 251                         p9_fid_put(fid);
 252                         fid = ERR_PTR(-ENOENT);
 253                 } else {
 254                         __add_fid(dentry, fid);
 255                         p9_fid_get(fid);
 256                         spin_unlock(&dentry->d_lock);
 257                 }
 258         }
 259 err_out:
 260         up_read(&v9ses->rename_sem);
 261         return fid;
 262 }
 263
 264 /**
 265  * v9fs_fid_lookup - lookup for a fid, try to walk if not found
 266  * @dentry: dentry to look for fid in
 267  *
 268  * Look for a fid in the specified dentry for the current user.
 269  * If no fid is found, try to create one walking from a fid from the parent
 270  * dentry (if it has one), or the root dentry. If the user haven't accessed
 271  * the fs yet, attach now and walk from the root.
 272  */
 273
 274 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 275 {
 276         kuid_t uid;
 277         int  any, access;
 278         struct v9fs_session_info *v9ses;
 279
 280         v9ses = v9fs_dentry2v9ses(dentry);
 281         access = v9ses->flags & V9FS_ACCESS_MASK;
 282         switch (access) {
 283         case V9FS_ACCESS_SINGLE:
 284         case V9FS_ACCESS_USER:
 285         case V9FS_ACCESS_CLIENT:
 286                 uid = current_fsuid();
 287                 any = 0;
 288                 break;
 289
 290         case V9FS_ACCESS_ANY:
 291                 uid = v9ses->uid;
 292                 any = 1;
 293                 break;
 294
 295         default:
 296                 uid = INVALID_UID;
 297                 any = 0;
 298                 break;
 299         }
 300         return v9fs_fid_lookup_with_uid(dentry, uid, any);
 301 }
 302
 303 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
 304 {
 305         int err;
 306         struct p9_fid *fid, *ofid;
 307
 308         ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0);
 309         fid = clone_fid(ofid);
 310         if (IS_ERR(fid))
 311                 goto error_out;
 312         p9_fid_put(ofid);
 313         /*
 314          * writeback fid will only be used to write back the
 315          * dirty pages. We always request for the open fid in read-write
 316          * mode so that a partial page write which result in page
 317          * read can work.
 318          */
 319         err = p9_client_open(fid, O_RDWR);
 320         if (err < 0) {
 321                 p9_fid_put(fid);
 322                 fid = ERR_PTR(err);
 323                 goto error_out;
 324         }
 325 error_out:
 326         return fid;
 327 }