fs/9p/vfs_dentry.c

   1 /*
   2  *  linux/fs/9p/vfs_dentry.c
   3  *
   4  * This file contians vfs dentry ops for the 9P2000 protocol.
   5  *
   6  *  Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
   7  *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
   8  *
   9  *  This program is free software; you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation; either version 2 of the License, or
  12  *  (at your option) any later version.
  13  *
  14  *  This program is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with this program; if not, write to:
  21  *  Free Software Foundation
  22  *  51 Franklin Street, Fifth Floor
  23  *  Boston, MA  02111-1301  USA
  24  *
  25  */
  26
  27 #include <linux/module.h>
  28 #include <linux/errno.h>
  29 #include <linux/fs.h>
  30 #include <linux/file.h>
  31 #include <linux/pagemap.h>
  32 #include <linux/stat.h>
  33 #include <linux/string.h>
  34 #include <linux/smp_lock.h>
  35 #include <linux/inet.h>
  36 #include <linux/namei.h>
  37 #include <linux/idr.h>
  38
  39 #include "debug.h"
  40 #include "v9fs.h"
  41 #include "9p.h"
  42 #include "v9fs_vfs.h"
  43 #include "fid.h"
  44
  45 /**
  46  * v9fs_dentry_validate - VFS dcache hook to validate cache
  47  * @dentry:  dentry that is being validated
  48  * @nd: path data
  49  *
  50  * dcache really shouldn't be used for 9P2000 as at all due to
  51  * potential attached semantics to directory traversal (walk).
  52  *
  53  * FUTURE: look into how to use dcache to allow multi-stage
  54  * walks in Plan 9 & potential for better dcache operation which
  55  * would remain valid for Plan 9 semantics.  Older versions
  56  * had validation via stat for those interested.  However, since
  57  * stat has the same approximate overhead as walk there really
  58  * is no difference.  The only improvement would be from a
  59  * time-decay cache like NFS has and that undermines the
  60  * synchronous nature of 9P2000.
  61  *
  62  */
  63
  64 static int v9fs_dentry_validate(struct dentry *dentry, struct nameidata *nd)
  65 {
  66         struct dentry *dc = current->fs->pwd;
  67
  68         dprintk(DEBUG_VFS, "dentry: %s (%p)\n", dentry->d_iname, dentry);
  69         if (v9fs_fid_lookup(dentry)) {
  70                 dprintk(DEBUG_VFS, "VALID\n");
  71                 return 1;
  72         }
  73
  74         while (dc != NULL) {
  75                 if (dc == dentry) {
  76                         dprintk(DEBUG_VFS, "VALID\n");
  77                         return 1;
  78                 }
  79                 if (dc == dc->d_parent)
  80                         break;
  81
  82                 dc = dc->d_parent;
  83         }
  84
  85         dprintk(DEBUG_VFS, "INVALID\n");
  86         return 0;
  87 }
  88
  89 /**
  90  * v9fs_dentry_release - called when dentry is going to be freed
  91  * @dentry:  dentry that is being release
  92  *
  93  */
  94
  95 void v9fs_dentry_release(struct dentry *dentry)
  96 {
  97         int err;
  98
  99         dprintk(DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
 100
 101         if (dentry->d_fsdata != NULL) {
 102                 struct list_head *fid_list = dentry->d_fsdata;
 103                 struct v9fs_fid *temp = NULL;
 104                 struct v9fs_fid *current_fid = NULL;
 105
 106                 list_for_each_entry_safe(current_fid, temp, fid_list, list) {
 107                         err = v9fs_t_clunk(current_fid->v9ses, current_fid->fid);
 108
 109                         if (err < 0)
 110                                 dprintk(DEBUG_ERROR, "clunk failed: %d name %s\n",
 111                                         err, dentry->d_iname);
 112
 113                         v9fs_fid_destroy(current_fid);
 114                 }
 115
 116                 kfree(dentry->d_fsdata);        /* free the list_head */
 117         }
 118 }
 119
 120 struct dentry_operations v9fs_dentry_operations = {
 121         .d_revalidate = v9fs_dentry_validate,
 122         .d_release = v9fs_dentry_release,
 123 };