9p: v9fs_fid_add() can't fail now
[linux-3.10.git] / fs / 9p / fid.c
index 08fa320..73ca550 100644 (file)
@@ -1,6 +1,7 @@
 /*
  * V9FS FID Management
  *
+ *  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
@@ -23,9 +24,9 @@
 #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 <asm/semaphore.h>
 #include <net/9p/9p.h>
 #include <net/9p/client.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
  *
  */
 
-int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
+void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
 {
-       struct v9fs_dentry *dent;
+       spin_lock(&dentry->d_lock);
+       hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
+       spin_unlock(&dentry->d_lock);
+}
 
-       P9_DPRINTK(P9_DEBUG_VFS, "fid %d dentry %s\n",
-                                       fid->fid, dentry->d_iname);
+/**
+ * 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
+ *
+ */
 
-       dent = dentry->d_fsdata;
-       if (!dent) {
-               dent = kmalloc(sizeof(struct v9fs_dentry), GFP_KERNEL);
-               if (!dent)
-                       return -ENOMEM;
+static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
+{
+       struct p9_fid *fid, *ret;
 
-               spin_lock_init(&dent->lock);
-               INIT_LIST_HEAD(&dent->fidlist);
-               dentry->d_fsdata = dent;
+       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);
        }
 
-       spin_lock(&dent->lock);
-       list_add(&fid->dlist, &dent->fidlist);
-       spin_unlock(&dent->lock);
-
-       return 0;
+       return ret;
 }
 
-/**
- * v9fs_fid_lookup - return a locked fid from a dentry
- * @dentry: dentry to look for fid in
- *
- * find a fid in the dentry, obtain its semaphore and return a reference to it.
- * code calling lookup is responsible for releasing lock
- *
- * TODO: only match fids that have the same uid as current user
- *
+/*
+ * We need to hold v9ses->rename_sem as long as we hold references
+ * to returned path array. Array element contain pointers to
+ * dentry names.
  */
-
-struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
+static int build_path_from_dentry(struct v9fs_session_info *v9ses,
+                                 struct dentry *dentry, char ***names)
 {
-       struct v9fs_dentry *dent;
-       struct p9_fid *fid;
+       int n = 0, i;
+       char **wnames;
+       struct dentry *ds;
 
-       P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
-       dent = dentry->d_fsdata;
-       if (dent)
-               fid = list_entry(dent->fidlist.next, struct p9_fid, dlist);
-       else
-               fid = ERR_PTR(-EBADF);
+       for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
+               n++;
 
-       P9_DPRINTK(P9_DEBUG_VFS, " fid: %p\n", fid);
-       return fid;
+       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;
 }
 
-struct p9_fid *v9fs_fid_lookup_remove(struct dentry *dentry)
+static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
+                                              kuid_t uid, int any)
 {
-       struct p9_fid *fid;
-       struct v9fs_dentry *dent;
+       struct dentry *ds;
+       char **wnames, *uname;
+       int i, n, l, clone, access;
+       struct v9fs_session_info *v9ses;
+       struct p9_fid *fid, *old_fid = NULL;
 
-       dent = dentry->d_fsdata;
-       fid = v9fs_fid_lookup(dentry);
-       if (!IS_ERR(fid)) {
-               spin_lock(&dent->lock);
-               list_del(&fid->dlist);
-               spin_unlock(&dent->lock);
+       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;
        }
+       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);
+       }
+       /* 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;
+               }
+               old_fid = fid;
+               i += l;
+               clone = 0;
+       }
+       kfree(wnames);
+fid_out:
+       if (!IS_ERR(fid))
+               v9fs_fid_add(dentry, fid);
+err_out:
+       up_read(&v9ses->rename_sem);
        return fid;
 }
 
-
 /**
- * v9fs_fid_clone - lookup the fid for a dentry, clone a private copy and
- *     release it
+ * v9fs_fid_lookup - lookup for a fid, try to walk if not found
  * @dentry: dentry to look for fid in
  *
- * find a fid in the dentry and then clone to a new private fid
- *
- * TODO: only match fids that have the same uid as current user
- *
+ * 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 p9_fid *v9fs_fid_lookup(struct dentry *dentry)
+{
+       kuid_t uid;
+       int  any, access;
+       struct v9fs_session_info *v9ses;
+
+       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);
+}
+
 struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
 {
-       struct p9_fid *ofid, *fid;
+       struct p9_fid *fid, *ret;
 
-       P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
-       ofid = v9fs_fid_lookup(dentry);
-       if (IS_ERR(ofid))
-               return ofid;
+       fid = v9fs_fid_lookup(dentry);
+       if (IS_ERR(fid))
+               return fid;
+
+       ret = p9_client_walk(fid, 0, NULL, 1);
+       return ret;
+}
+
+static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, kuid_t uid)
+{
+       struct p9_fid *fid, *ret;
+
+       fid = v9fs_fid_lookup_with_uid(dentry, uid, 0);
+       if (IS_ERR(fid))
+               return fid;
 
-       fid = p9_client_walk(ofid, 0, NULL, 1);
+       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;
 }