{
struct vfsmount *parent;
struct dentry *mountpoint;
- spin_lock(&vfsmount_lock);
+
+ br_read_lock(vfsmount_lock);
parent = path->mnt->mnt_parent;
if (parent == path->mnt) {
- spin_unlock(&vfsmount_lock);
+ br_read_unlock(vfsmount_lock);
return 0;
}
mntget(parent);
mountpoint = dget(path->mnt->mnt_mountpoint);
- spin_unlock(&vfsmount_lock);
+ br_read_unlock(vfsmount_lock);
dput(path->dentry);
path->dentry = mountpoint;
mntput(path->mnt);
follow_mount(&nd->path);
}
+/*
+ * Allocate a dentry with name and parent, and perform a parent
+ * directory ->lookup on it. Returns the new dentry, or ERR_PTR
+ * on error. parent->d_inode->i_mutex must be held. d_lookup must
+ * have verified that no child exists while under i_mutex.
+ */
+static struct dentry *d_alloc_and_lookup(struct dentry *parent,
+ struct qstr *name, struct nameidata *nd)
+{
+ struct inode *inode = parent->d_inode;
+ struct dentry *dentry;
+ struct dentry *old;
+
+ /* Don't create child dentry for a dead directory. */
+ if (unlikely(IS_DEADDIR(inode)))
+ return ERR_PTR(-ENOENT);
+
+ dentry = d_alloc(parent, name);
+ if (unlikely(!dentry))
+ return ERR_PTR(-ENOMEM);
+
+ old = inode->i_op->lookup(inode, dentry, nd);
+ if (unlikely(old)) {
+ dput(dentry);
+ dentry = old;
+ }
+ return dentry;
+}
+
/*
* It's more convoluted than I'd like it to be, but... it's still fairly
* small and for now I'd prefer to have fast path as straight as possible.
return err;
}
+ /*
+ * Rename seqlock is not required here because in the off chance
+ * of a false negative due to a concurrent rename, we're going to
+ * do the non-racy lookup, below.
+ */
dentry = __d_lookup(nd->path.dentry, name);
if (!dentry)
goto need_lookup;
+found:
if (dentry->d_op && dentry->d_op->d_revalidate)
goto need_revalidate;
done:
mutex_lock(&dir->i_mutex);
/*
* First re-do the cached lookup just in case it was created
- * while we waited for the directory semaphore..
+ * while we waited for the directory semaphore, or the first
+ * lookup failed due to an unrelated rename.
*
- * FIXME! This could use version numbering or similar to
- * avoid unnecessary cache lookups.
- *
- * The "dcache_lock" is purely to protect the RCU list walker
- * from concurrent renames at this point (we mustn't get false
- * negatives from the RCU list walk here, unlike the optimistic
- * fast walk).
- *
- * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
+ * This could use version numbering or similar to avoid unnecessary
+ * cache lookups, but then we'd have to do the first lookup in the
+ * non-racy way. However in the common case here, everything should
+ * be hot in cache, so would it be a big win?
*/
dentry = d_lookup(parent, name);
- if (!dentry) {
- struct dentry *new;
-
- /* Don't create child dentry for a dead directory. */
- dentry = ERR_PTR(-ENOENT);
- if (IS_DEADDIR(dir))
- goto out_unlock;
-
- new = d_alloc(parent, name);
- dentry = ERR_PTR(-ENOMEM);
- if (new) {
- dentry = dir->i_op->lookup(dir, new, nd);
- if (dentry)
- dput(new);
- else
- dentry = new;
- }
-out_unlock:
+ if (likely(!dentry)) {
+ dentry = d_alloc_and_lookup(parent, name, nd);
mutex_unlock(&dir->i_mutex);
if (IS_ERR(dentry))
goto fail;
goto done;
}
-
/*
* Uhhuh! Nasty case: the cache was re-populated while
* we waited on the semaphore. Need to revalidate.
*/
mutex_unlock(&dir->i_mutex);
- if (dentry->d_op && dentry->d_op->d_revalidate) {
- dentry = do_revalidate(dentry, nd);
- if (!dentry)
- dentry = ERR_PTR(-ENOENT);
- }
- if (IS_ERR(dentry))
- goto fail;
- goto done;
+ goto found;
need_revalidate:
dentry = do_revalidate(dentry, nd);
goto out;
}
- dentry = __d_lookup(base, name);
-
- /* lockess __d_lookup may fail due to concurrent d_move()
- * in some unrelated directory, so try with d_lookup
+ /*
+ * Don't bother with __d_lookup: callers are for creat as
+ * well as unlink, so a lot of the time it would cost
+ * a double lookup.
*/
- if (!dentry)
- dentry = d_lookup(base, name);
+ dentry = d_lookup(base, name);
if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
dentry = do_revalidate(dentry, nd);
- if (!dentry) {
- struct dentry *new;
-
- /* Don't create child dentry for a dead directory. */
- dentry = ERR_PTR(-ENOENT);
- if (IS_DEADDIR(inode))
- goto out;
-
- new = d_alloc(base, name);
- dentry = ERR_PTR(-ENOMEM);
- if (!new)
- goto out;
- dentry = inode->i_op->lookup(inode, new, nd);
- if (!dentry)
- dentry = new;
- else
- dput(new);
- }
+ if (!dentry)
+ dentry = d_alloc_and_lookup(base, name, nd);
out:
return dentry;
}
git.openpandora.org / pandora-kernel.git / blobdiff