9p: v9fs_fid_add() can't fail now
[linux-3.10.git] / fs / 9p / fid.c
index a43e4ab..73ca550 100644 (file)
@@ -24,6 +24,7 @@
 #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>
  *
  */
 
-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;
-
-       P9_DPRINTK(P9_DEBUG_VFS, "fid %d dentry %s\n",
-                                       fid->fid, dentry->d_iname);
-
-       dent = dentry->d_fsdata;
-       if (!dent) {
-               dent = kmalloc(sizeof(struct v9fs_dentry), GFP_KERNEL);
-               if (!dent)
-                       return -ENOMEM;
-
-               spin_lock_init(&dent->lock);
-               INIT_LIST_HEAD(&dent->fidlist);
-               dentry->d_fsdata = dent;
-       }
-
-       spin_lock(&dent->lock);
-       list_add(&fid->dlist, &dent->fidlist);
-       spin_unlock(&dent->lock);
-
-       return 0;
+       spin_lock(&dentry->d_lock);
+       hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
+       spin_unlock(&dentry->d_lock);
 }
 
 /**
@@ -73,29 +56,155 @@ int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
  *
  */
 
-static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any)
+static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
 {
-       struct v9fs_dentry *dent;
        struct p9_fid *fid, *ret;
 
-       P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n",
-               dentry->d_iname, dentry, uid, any);
-       dent = (struct v9fs_dentry *) dentry->d_fsdata;
+       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;
-       if (dent) {
-               spin_lock(&dent->lock);
-               list_for_each_entry(fid, &dent->fidlist, dlist) {
-                       if (any || fid->uid == uid) {
+       /* 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(&dent->lock);
+               spin_unlock(&dentry->d_lock);
        }
 
        return ret;
 }
 
+/*
+ * We need to hold v9ses->rename_sem as long as we hold references
+ * to returned path array. Array element contain pointers to
+ * dentry names.
+ */
+static int build_path_from_dentry(struct v9fs_session_info *v9ses,
+                                 struct dentry *dentry, char ***names)
+{
+       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;
+}
+
+static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
+                                              kuid_t uid, int any)
+{
+       struct dentry *ds;
+       char **wnames, *uname;
+       int i, n, l, clone, access;
+       struct v9fs_session_info *v9ses;
+       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;
+       }
+       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_lookup - lookup for a fid, try to walk if not found
  * @dentry: dentry to look for fid in
@@ -108,18 +217,16 @@ static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any)
 
 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 {
-       int i, n, l, clone, any, access;
-       u32 uid;
-       struct p9_fid *fid;
-       struct dentry *d, *ds;
+       kuid_t uid;
+       int  any, access;
        struct v9fs_session_info *v9ses;
-       char **wnames, *uname;
 
-       v9ses = v9fs_inode2v9ses(dentry->d_inode);
+       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;
@@ -130,80 +237,57 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
                break;
 
        default:
-               uid = ~0;
+               uid = INVALID_UID;
                any = 0;
                break;
        }
+       return v9fs_fid_lookup_with_uid(dentry, uid, any);
+}
 
-       fid = v9fs_fid_find(dentry, uid, any);
-       if (fid)
-               return fid;
-
-       ds = dentry->d_parent;
-       fid = v9fs_fid_find(ds, uid, any);
-       if (!fid) { /* walk from the root */
-               n = 0;
-               for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
-                       n++;
-
-               fid = v9fs_fid_find(ds, uid, any);
-               if (!fid) { /* the user is not attached to the fs yet */
-                       if (access == V9FS_ACCESS_SINGLE)
-                               return ERR_PTR(-EPERM);
-
-                       if (v9fs_extended(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(ds, fid);
-               }
-       } else /* walk from the parent */
-               n = 1;
+struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
+{
+       struct p9_fid *fid, *ret;
 
-       if (ds == dentry)
+       fid = v9fs_fid_lookup(dentry);
+       if (IS_ERR(fid))
                return fid;
 
-       wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
-       if (!wnames)
-               return ERR_PTR(-ENOMEM);
-
-       for (d = dentry, i = (n-1); i >= 0; i--, d = d->d_parent)
-               wnames[i] = (char *) d->d_name.name;
-
-       clone = 1;
-       i = 0;
-       while (i < n) {
-               l = min(n - i, P9_MAXWELEM);
-               fid = p9_client_walk(fid, l, &wnames[i], clone);
-               if (IS_ERR(fid)) {
-                       kfree(wnames);
-                       return fid;
-               }
-
-               i += l;
-               clone = 0;
-       }
-
-       kfree(wnames);
-       v9fs_fid_add(dentry, fid);
-       return fid;
+       ret = p9_client_walk(fid, 0, NULL, 1);
+       return ret;
 }
 
-struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
+static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, kuid_t uid)
 {
        struct p9_fid *fid, *ret;
 
-       fid = v9fs_fid_lookup(dentry);
+       fid = v9fs_fid_lookup_with_uid(dentry, uid, 0);
        if (IS_ERR(fid))
                return fid;
 
        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;
+}