From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59E2A221FC8 for ; Mon, 20 Oct 2025 17:29:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760981343; cv=none; b=o+9jpV+OqVnPKVAx5yHICTKXdV5Q90JVO9XljK7RdnJL+tmfVXRDjIb4hBV1+I54xDZsr4Au7L2JwfQdQy7edcdCOSOsNCOPw13GMQKnnXVmh9wVVPiOkIP5i0O/SCwlm4U9ba5kgrI0DFhXUsZIzsdTAaq+iUmVmdvb3Nuyjgg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760981343; c=relaxed/simple; bh=POeUuxRxNO9gA6/UVY+tBhszzkiDL6YNaCVyIoaTS2I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TIdXy1s5GFqzI9aSF+G6hARDNUcvIOAdvcIADOfb2+LU0YFMeSBsRwr/0xRzVe28pa27yR8OcCA2QgRjVt6g9e8YAUQEZrXpqUcw8S6sHWfVbIBNSMMtWAD5E2A4hzy1DyVYG6IEpMmuamRIvXC5pkdS5/5sI3j/KBS0C+F6CBw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fmaTkTS4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fmaTkTS4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68B58C4CEF9; Mon, 20 Oct 2025 17:29:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760981343; bh=POeUuxRxNO9gA6/UVY+tBhszzkiDL6YNaCVyIoaTS2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fmaTkTS47fynYY/6rBSlX45NE41wk33n5/KUcv5UxEMAILkADRfRzISECZRNkHK+B 0hDWSssNeHxlFu+bEDPq9g6QzriQY7q9ma6B0y8qhi2qEjlpKILnQQzqHby040rXIo QaHenKofw6V7GE/vAsk4A2+b8qdoSWbRh04SJeXlBt12AHHjWlVty3y7x5oFW8MkgI 6214k0tkS9dvBzWJrn6TDFMQxRzMMthRVGLYhUlURAjLDvRZRXsf0o23Eh6cw8lxMX 7B0MNpF0qY/SjvNEsUIG3JVwVzksp00lpcSU35AnqFvMOWiT22jG/3hHvTArVRleqe TKuPBLlm/jUiA== From: Sasha Levin To: stable@vger.kernel.org Cc: Al Viro , Christian Brauner , Sasha Levin Subject: [PATCH 6.12.y 1/2] d_alloc_parallel(): set DCACHE_PAR_LOOKUP earlier Date: Mon, 20 Oct 2025 13:28:58 -0400 Message-ID: <20251020172900.1851256-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025102038-hash-smashing-4b29@gregkh> References: <2025102038-hash-smashing-4b29@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Al Viro [ Upstream commit e95db51c81f54dd12ea465b5127e4786f62a1095 ] Do that before new dentry is visible anywhere. It does create a new possible state for dentries present in ->d_children/->d_sib - DCACHE_PAR_LOOKUP present, negative, unhashed, not in in-lookup hash chains, refcount positive. Those are going to be skipped by all tree-walkers (both d_walk() callbacks in fs/dcache.c and explicit loops over children/sibling lists elsewhere) and dput() is fine with those. NOTE: dropping the final reference to a "normal" in-lookup dentry (in in-lookup hash) is a bug - somebody must've forgotten to call d_lookup_done() on it and bad things will happen. With those it's OK; if/when we get around to making __dentry_kill() complain about such breakage, remember that predicate to check should *not* be just d_in_lookup(victim) but rather a combination of that with !hlist_bl_unhashed(&victim->d_u.d_in_lookup_hash). Might be worth considering later... Reviewed-by: Christian Brauner Signed-off-by: Al Viro Stable-dep-of: 56094ad3eaa2 ("vfs: Don't leak disconnected dentries on umount") Signed-off-by: Sasha Levin --- fs/dcache.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index 0f6b16ba30d08..d81765352cf81 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2475,13 +2475,19 @@ struct dentry *d_alloc_parallel(struct dentry *parent, unsigned int hash = name->hash; struct hlist_bl_head *b = in_lookup_hash(parent, hash); struct hlist_bl_node *node; - struct dentry *new = d_alloc(parent, name); + struct dentry *new = __d_alloc(parent->d_sb, name); struct dentry *dentry; unsigned seq, r_seq, d_seq; if (unlikely(!new)) return ERR_PTR(-ENOMEM); + new->d_flags |= DCACHE_PAR_LOOKUP; + spin_lock(&parent->d_lock); + new->d_parent = dget_dlock(parent); + hlist_add_head(&new->d_sib, &parent->d_children); + spin_unlock(&parent->d_lock); + retry: rcu_read_lock(); seq = smp_load_acquire(&parent->d_inode->i_dir_seq); @@ -2565,8 +2571,6 @@ struct dentry *d_alloc_parallel(struct dentry *parent, return dentry; } rcu_read_unlock(); - /* we can't take ->d_lock here; it's OK, though. */ - new->d_flags |= DCACHE_PAR_LOOKUP; new->d_wait = wq; hlist_bl_add_head(&new->d_u.d_in_lookup_hash, b); hlist_bl_unlock(b); -- 2.51.0