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From: Stefan Berger <stefanb@linux.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: zohar@linux.ibm.com, gregkh@linuxfoundation.org,
	initramfs@vger.kernel.org, Stefan Berger <stefanb@linux.ibm.com>,
	stable@vger.kernel.org, Rob Landley <rob@landley.net>
Subject: [PATCH v2] rootfs: Fix support for rootfstype= when root= is given
Date: Tue, 14 Nov 2023 09:10:30 -0500	[thread overview]
Message-ID: <20231114141030.219729-1-stefanb@linux.ibm.com> (raw)

Documentation/filesystems/ramfs-rootfs-initramfs.rst states:

  If CONFIG_TMPFS is enabled, rootfs will use tmpfs instead of ramfs by
  default.  To force ramfs, add "rootfstype=ramfs" to the kernel command
  line.

This currently does not work when root= is provided since then
saved_root_name contains a string and initfstype= is ignored. Therefore,
ramfs is currently always chosen when root= is provided.

The current behavior for rootfs's filesystem is:

   root=       | initfstype= | chosen rootfs filesystem
   ------------+-------------+--------------------------
   unspecified | unspecified | tmpfs
   unspecified | tmpfs       | tmpfs
   unspecified | ramfs       | ramfs
    provided   | ignored     | ramfs

initfstype= should be respected regardless whether root= is given,
as shown below:

   root=       | initfstype= | chosen rootfs filesystem
   ------------+-------------+--------------------------
   unspecified | unspecified | tmpfs  (as before)
   unspecified | tmpfs       | tmpfs  (as before)
   unspecified | ramfs       | ramfs  (as before)
    provided   | unspecified | ramfs  (compatibility with before)
    provided   | tmpfs       | tmpfs  (new)
    provided   | ramfs       | ramfs  (new)

This table represents the new behavior.

Fixes: 6e19eded3684 ("initmpfs: use initramfs if rootfstype= or root=  specified")
Cc: <stable@vger.kernel.org>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Rob Landley <rob@landley.net>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 init/do_mounts.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 5fdef94f0864..279ad28bf4fb 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -510,7 +510,10 @@ 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")))
-		is_tmpfs = true;
+	if (IS_ENABLED(CONFIG_TMPFS)) {
+		if (!saved_root_name[0] && !root_fs_names)
+			is_tmpfs = true;
+		else if (root_fs_names && !!strstr(root_fs_names, "tmpfs"))
+			is_tmpfs = true;
+	}
 }
-- 
2.41.0


             reply	other threads:[~2023-11-14 14:10 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-14 14:10 Stefan Berger [this message]
2023-11-15 11:04 ` [PATCH v2] rootfs: Fix support for rootfstype= when root= is given Greg KH
2023-11-19 14:12 ` Mimi Zohar

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