linux-kernel - [PATCH 5/5] fix rootfstype=tmpfs

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Message-ID: <8244c75f-445e-b15b-9dbf-266e7ca666e2@landley.net>
Date:   Tue, 21 Feb 2023 15:04:15 -0600
From:   Rob Landley <rob@...dley.net>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>
Subject: [PATCH 5/5] fix rootfstype=tmpfs

Wire up rootfstype=tmpfs to force rootfs to be tmpfs even when you specify root=

Initramfs automatically uses tmpfs (if available) when you DON'T specify a
root= fallback root to mount over initramfs, but some people can't NOT do
that for some reason (old bootloaders), so let rootfstype=tmpfs override it.

My original code tried to do this 10 years ago but got the test wrong,
and nobody's corrected it since, so here you go...

Signed-off-by: Rob Landley <rob@...dley.net>

See https://lkml.iu.edu/hypermail/linux/kernel/2207.3/06939.html
---
 init/do_mounts.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 811e94daf0a8..01d80fb828fd 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -665,7 +665,7 @@ struct file_system_type rootfs_fs_type = {
 
 void __init init_rootfs(void)
 {
-	if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] &&
-		(!root_fs_names || strstr(root_fs_names, "tmpfs")))
+	if (IS_ENABLED(CONFIG_TMPFS) && (!root_fs_names ? !saved_root_name[0] :
+		!!strstr(root_fs_names, "tmpfs")))
 		is_tmpfs = true;
 }