Commit 2e2e88ea authored Aug 18, 2010 by Nick Piggin Committed by Al Viro Aug 18, 2010

fs: fix do_lookup false negative



fs: fix do_lookup false negative

In do_lookup, if we initially find no dentry, we take the directory i_mutex and
re-check the lookup. If we find a dentry there, then we revalidate it if
needed. However if that revalidate asks for the dentry to be invalidated, we
return -ENOENT from do_lookup. What should happen instead is an attempt to
allocate and lookup a new dentry.

This is probably not noticed because it is rare. It is only reached if a
concurrent create races in first (in which case, the dentry probably won't be
invalidated anyway), or if the racy __d_lookup has failed due to a
false-negative (which is very rare).

Fix this by removing code and have it use the normal reval path.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent 3a48ee8a

fs/namei.c

+2 −8

Original line number	Diff line number	Diff line
		@@ -709,6 +709,7 @@ static int do_lookup(struct nameidata nd, struct qstr name,
		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:
		@@ -766,14 +767,7 @@ static int do_lookup(struct nameidata nd, struct qstr name,
		* 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);