9p: v9fs_fid_add() can't fail now
[linux-3.10.git] / fs / 9p / fid.c
index d95f862..73ca550 100644 (file)
@@ -1,12 +1,12 @@
 /*
  * V9FS FID Management
  *
- *  Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
+ *  Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
+ *  Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
  *
  *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *
  */
 
-#include <linux/config.h>
 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
 #include <linux/idr.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
 
-#include "debug.h"
 #include "v9fs.h"
-#include "9p.h"
 #include "v9fs_vfs.h"
-#include "transport.h"
-#include "mux.h"
-#include "conv.h"
 #include "fid.h"
 
 /**
- * v9fs_fid_insert - add a fid to a dentry
+ * v9fs_fid_add - add a fid to a dentry
+ * @dentry: dentry that the fid is being added to
  * @fid: fid to add
- * @dentry: dentry that it is being added to
  *
  */
 
-static int v9fs_fid_insert(struct v9fs_fid *fid, struct dentry *dentry)
+void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
 {
-       struct list_head *fid_list = (struct list_head *)dentry->d_fsdata;
-       dprintk(DEBUG_9P, "fid %d (%p) dentry %s (%p)\n", fid->fid, fid,
-               dentry->d_iname, dentry);
-       if (dentry->d_fsdata == NULL) {
-               dentry->d_fsdata =
-                   kmalloc(sizeof(struct list_head), GFP_KERNEL);
-               if (dentry->d_fsdata == NULL) {
-                       dprintk(DEBUG_ERROR, "Out of memory\n");
-                       return -ENOMEM;
-               }
-               fid_list = (struct list_head *)dentry->d_fsdata;
-               INIT_LIST_HEAD(fid_list);       /* Initialize list head */
-       }
-
-       fid->uid = current->uid;
-       fid->pid = current->pid;
-       list_add(&fid->list, fid_list);
-       return 0;
+       spin_lock(&dentry->d_lock);
+       hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
+       spin_unlock(&dentry->d_lock);
 }
 
 /**
- * v9fs_fid_create - allocate a FID structure
- * @dentry - dentry to link newly created fid to
+ * v9fs_fid_find - retrieve a fid that belongs to the specified uid
+ * @dentry: dentry to look for fid in
+ * @uid: return fid that belongs to the specified user
+ * @any: if non-zero, return any fid associated with the dentry
  *
  */
 
-struct v9fs_fid *v9fs_fid_create(struct dentry *dentry,
-       struct v9fs_session_info *v9ses, int fid, int create)
+static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
 {
-       struct v9fs_fid *new;
+       struct p9_fid *fid, *ret;
 
-       dprintk(DEBUG_9P, "fid create dentry %p, fid %d, create %d\n",
-               dentry, fid, create);
-
-       new = kmalloc(sizeof(struct v9fs_fid), GFP_KERNEL);
-       if (new == NULL) {
-               dprintk(DEBUG_ERROR, "Out of Memory\n");
-               return ERR_PTR(-ENOMEM);
+       p9_debug(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n",
+                dentry->d_name.name, dentry, from_kuid(&init_user_ns, uid),
+                any);
+       ret = NULL;
+       /* we'll recheck under lock if there's anything to look in */
+       if (dentry->d_fsdata) {
+               struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
+               struct hlist_node *n;
+               spin_lock(&dentry->d_lock);
+               hlist_for_each_entry(fid, n, h, dlist) {
+                       if (any || uid_eq(fid->uid, uid)) {
+                               ret = fid;
+                               break;
+                       }
+               }
+               spin_unlock(&dentry->d_lock);
        }
 
-       new->fid = fid;
-       new->v9ses = v9ses;
-       new->fidopen = 0;
-       new->fidcreate = create;
-       new->fidclunked = 0;
-       new->iounit = 0;
-       new->rdir_pos = 0;
-       new->rdir_fcall = NULL;
-
-       if (v9fs_fid_insert(new, dentry) == 0)
-               return new;
-       else {
-               dprintk(DEBUG_ERROR, "Problems inserting to dentry\n");
-               kfree(new);
-               return NULL;
-       }
+       return ret;
 }
 
-/**
- * v9fs_fid_destroy - deallocate a FID structure
- * @fid: fid to destroy
- *
+/*
+ * We need to hold v9ses->rename_sem as long as we hold references
+ * to returned path array. Array element contain pointers to
+ * dentry names.
  */
-
-void v9fs_fid_destroy(struct v9fs_fid *fid)
+static int build_path_from_dentry(struct v9fs_session_info *v9ses,
+                                 struct dentry *dentry, char ***names)
 {
-       list_del(&fid->list);
-       kfree(fid);
+       int n = 0, i;
+       char **wnames;
+       struct dentry *ds;
+
+       for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
+               n++;
+
+       wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
+       if (!wnames)
+               goto err_out;
+
+       for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
+               wnames[i] = (char  *)ds->d_name.name;
+
+       *names = wnames;
+       return n;
+err_out:
+       return -ENOMEM;
 }
 
-/**
- * v9fs_fid_walk_up - walks from the process current directory
- *     up to the specified dentry.
- */
-static struct v9fs_fid *v9fs_fid_walk_up(struct dentry *dentry)
+static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
+                                              kuid_t uid, int any)
 {
-       int fidnum, cfidnum, err;
-       struct v9fs_fid *cfid;
-       struct dentry *cde;
+       struct dentry *ds;
+       char **wnames, *uname;
+       int i, n, l, clone, access;
        struct v9fs_session_info *v9ses;
-
-       v9ses = v9fs_inode2v9ses(current->fs->pwd->d_inode);
-       cfid = v9fs_fid_lookup(current->fs->pwd);
-       if (cfid == NULL) {
-               dprintk(DEBUG_ERROR, "process cwd doesn't have a fid\n");
-               return ERR_PTR(-ENOENT);
+       struct p9_fid *fid, *old_fid = NULL;
+
+       v9ses = v9fs_dentry2v9ses(dentry);
+       access = v9ses->flags & V9FS_ACCESS_MASK;
+       fid = v9fs_fid_find(dentry, uid, any);
+       if (fid)
+               return fid;
+       /*
+        * we don't have a matching fid. To do a TWALK we need
+        * parent fid. We need to prevent rename when we want to
+        * look at the parent.
+        */
+       down_read(&v9ses->rename_sem);
+       ds = dentry->d_parent;
+       fid = v9fs_fid_find(ds, uid, any);
+       if (fid) {
+               /* Found the parent fid do a lookup with that */
+               fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1);
+               goto fid_out;
        }
-
-       cfidnum = cfid->fid;
-       cde = current->fs->pwd;
-       /* TODO: take advantage of multiwalk */
-
-       fidnum = v9fs_get_idpool(&v9ses->fidpool);
-       if (fidnum < 0) {
-               dprintk(DEBUG_ERROR, "could not get a new fid num\n");
-               err = -ENOENT;
-               goto clunk_fid;
+       up_read(&v9ses->rename_sem);
+
+       /* start from the root and try to do a lookup */
+       fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
+       if (!fid) {
+               /* the user is not attached to the fs yet */
+               if (access == V9FS_ACCESS_SINGLE)
+                       return ERR_PTR(-EPERM);
+
+               if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
+                               uname = NULL;
+               else
+                       uname = v9ses->uname;
+
+               fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
+                                      v9ses->aname);
+               if (IS_ERR(fid))
+                       return fid;
+
+               v9fs_fid_add(dentry->d_sb->s_root, fid);
        }
-
-       while (cde != dentry) {
-               if (cde == cde->d_parent) {
-                       dprintk(DEBUG_ERROR, "can't find dentry\n");
-                       err = -ENOENT;
-                       goto clunk_fid;
-               }
-
-               err = v9fs_t_walk(v9ses, cfidnum, fidnum, "..", NULL);
-               if (err < 0) {
-                       dprintk(DEBUG_ERROR, "problem walking to parent\n");
-                       goto clunk_fid;
+       /* If we are root ourself just return that */
+       if (dentry->d_sb->s_root == dentry)
+               return fid;
+       /*
+        * Do a multipath walk with attached root.
+        * When walking parent we need to make sure we
+        * don't have a parallel rename happening
+        */
+       down_read(&v9ses->rename_sem);
+       n  = build_path_from_dentry(v9ses, dentry, &wnames);
+       if (n < 0) {
+               fid = ERR_PTR(n);
+               goto err_out;
+       }
+       clone = 1;
+       i = 0;
+       while (i < n) {
+               l = min(n - i, P9_MAXWELEM);
+               /*
+                * We need to hold rename lock when doing a multipath
+                * walk to ensure none of the patch component change
+                */
+               fid = p9_client_walk(fid, l, &wnames[i], clone);
+               if (IS_ERR(fid)) {
+                       if (old_fid) {
+                               /*
+                                * If we fail, clunk fid which are mapping
+                                * to path component and not the last component
+                                * of the path.
+                                */
+                               p9_client_clunk(old_fid);
+                       }
+                       kfree(wnames);
+                       goto err_out;
                }
-
-               cfidnum = fidnum;
-               cde = cde->d_parent;
+               old_fid = fid;
+               i += l;
+               clone = 0;
        }
-
-       return v9fs_fid_create(dentry, v9ses, fidnum, 0);
-
-clunk_fid:
-       v9fs_t_clunk(v9ses, fidnum, NULL);
-       return ERR_PTR(err);
+       kfree(wnames);
+fid_out:
+       if (!IS_ERR(fid))
+               v9fs_fid_add(dentry, fid);
+err_out:
+       up_read(&v9ses->rename_sem);
+       return fid;
 }
 
 /**
- * v9fs_fid_lookup - retrieve the right fid from a  particular dentry
+ * v9fs_fid_lookup - lookup for a fid, try to walk if not found
  * @dentry: dentry to look for fid in
- * @type: intent of lookup (operation or traversal)
- *
- * search list of fids associated with a dentry for a fid with a matching
- * thread id or uid.  If that fails, look up the dentry's parents to see if you
- * can find a matching fid.
  *
+ * Look for a fid in the specified dentry for the current user.
+ * If no fid is found, try to create one walking from a fid from the parent
+ * dentry (if it has one), or the root dentry. If the user haven't accessed
+ * the fs yet, attach now and walk from the root.
  */
 
-struct v9fs_fid *v9fs_fid_lookup(struct dentry *dentry)
+struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 {
-       struct list_head *fid_list = (struct list_head *)dentry->d_fsdata;
-       struct v9fs_fid *current_fid = NULL;
-       struct v9fs_fid *temp = NULL;
-       struct v9fs_fid *return_fid = NULL;
-
-       dprintk(DEBUG_9P, " dentry: %s (%p)\n", dentry->d_iname, dentry);
-
-       if (fid_list) {
-               list_for_each_entry_safe(current_fid, temp, fid_list, list) {
-                       if (!current_fid->fidcreate) {
-                               return_fid = current_fid;
-                               break;
-                       }
-               }
-
-               if (!return_fid)
-                       return_fid = current_fid;
-       }
+       kuid_t uid;
+       int  any, access;
+       struct v9fs_session_info *v9ses;
 
-       /* we are at the root but didn't match */
-       if ((!return_fid) && (dentry->d_parent == dentry)) {
-               /* TODO: clone attach with new uid */
-               return_fid = current_fid;
+       v9ses = v9fs_dentry2v9ses(dentry);
+       access = v9ses->flags & V9FS_ACCESS_MASK;
+       switch (access) {
+       case V9FS_ACCESS_SINGLE:
+       case V9FS_ACCESS_USER:
+       case V9FS_ACCESS_CLIENT:
+               uid = current_fsuid();
+               any = 0;
+               break;
+
+       case V9FS_ACCESS_ANY:
+               uid = v9ses->uid;
+               any = 1;
+               break;
+
+       default:
+               uid = INVALID_UID;
+               any = 0;
+               break;
        }
+       return v9fs_fid_lookup_with_uid(dentry, uid, any);
+}
 
-       if (!return_fid) {
-               struct dentry *par = current->fs->pwd->d_parent;
-               int count = 1;
-               while (par != NULL) {
-                       if (par == dentry)
-                               break;
-                       count++;
-                       if (par == par->d_parent) {
-                               dprintk(DEBUG_ERROR,
-                                       "got to root without finding dentry\n");
-                               break;
-                       }
-                       par = par->d_parent;
-               }
+struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
+{
+       struct p9_fid *fid, *ret;
 
-/* XXX - there may be some duplication we can get rid of */
-               if (par == dentry) {
-                       return_fid = v9fs_fid_walk_up(dentry);
-                       if (IS_ERR(return_fid))
-                               return_fid = NULL;
-               }
-       }
+       fid = v9fs_fid_lookup(dentry);
+       if (IS_ERR(fid))
+               return fid;
 
-       return return_fid;
+       ret = p9_client_walk(fid, 0, NULL, 1);
+       return ret;
 }
 
-struct v9fs_fid *v9fs_fid_get_created(struct dentry *dentry)
+static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, kuid_t uid)
 {
-       struct list_head *fid_list;
-       struct v9fs_fid *fid, *ftmp, *ret;
+       struct p9_fid *fid, *ret;
 
-       dprintk(DEBUG_9P, " dentry: %s (%p)\n", dentry->d_iname, dentry);
-       fid_list = (struct list_head *)dentry->d_fsdata;
-       ret = NULL;
-       if (fid_list) {
-               list_for_each_entry_safe(fid, ftmp, fid_list, list) {
-                       if (fid->fidcreate && fid->pid == current->pid) {
-                               list_del(&fid->list);
-                               ret = fid;
-                               break;
-                       }
-               }
-       }
+       fid = v9fs_fid_lookup_with_uid(dentry, uid, 0);
+       if (IS_ERR(fid))
+               return fid;
 
-       dprintk(DEBUG_9P, "return %p\n", ret);
+       ret = p9_client_walk(fid, 0, NULL, 1);
        return ret;
 }
+
+struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
+{
+       int err;
+       struct p9_fid *fid;
+
+       fid = v9fs_fid_clone_with_uid(dentry, GLOBAL_ROOT_UID);
+       if (IS_ERR(fid))
+               goto error_out;
+       /*
+        * writeback fid will only be used to write back the
+        * dirty pages. We always request for the open fid in read-write
+        * mode so that a partial page write which result in page
+        * read can work.
+        */
+       err = p9_client_open(fid, O_RDWR);
+       if (err < 0) {
+               p9_client_clunk(fid);
+               fid = ERR_PTR(err);
+               goto error_out;
+       }
+error_out:
+       return fid;
+}