[patch-2.4.0-test13-pre3] rootfs (2nd attempt)

From: Tigran Aivazian <tigran@veritas.com>
To: torvalds@transmeta.com
Cc: Andries.Brouwer@cwi.nl, Peter Samuelson <peter@cadcamlab.org>,
	linux-kernel@vger.kernel.org
Subject: [patch-2.4.0-test13-pre3] rootfs (2nd attempt)
Date: Mon, 18 Dec 2000 16:00:45 +0000 (GMT)	[thread overview]
Message-ID: <Pine.LNX.4.21.0012181547500.830-100000@penguin.homenet> (raw)
In-Reply-To: <20001218092219.H3199@cadcamlab.org>

Hi Linus,

Thanks to suggestions from Andries and Peter I enhanced the rootfs patch
to do the same it did before + panic when rootfs= is given but failed to
match the userspace mount(8) behaviour. Also other cleanups mentioned in
the thread are all incorporated (well, at least the sensible ones). Now,
everyone is (hopefully) happy.

Tested under 2.4.0-test13-pre3.

Regards,
Tigran

diff -urN -X dontdiff linux/Documentation/kernel-parameters.txt rootfs/Documentation/kernel-parameters.txt

--- linux/Documentation/kernel-parameters.txt	Tue Sep  5 21:51:14 2000
+++ rootfs/Documentation/kernel-parameters.txt	Mon Dec 18 09:04:06 2000
@@ -473,7 +473,10 @@
 
 	ro		[KNL] Mount root device read-only on boot.
 
-	root=		[KNL] root filesystem.
+	root=		[KNL] Mount root filesystem on specified (as hex or "/dev/XXX") device.
+
+	rootfs=		[KNL] Use filesystem type specified (e.g. rootfs=ext2) for root.
+ 
 
 	rw		[KNL] Mount root device read-write on boot.
 
diff -urN -X dontdiff linux/fs/super.c rootfs/fs/super.c
--- linux/fs/super.c	Tue Dec 12 09:25:22 2000
+++ rootfs/fs/super.c	Mon Dec 18 14:49:08 2000
@@ -18,6 +18,7 @@
  *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
  *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
  *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
+ *  Added rootfs boot param. used by mount_root(): Tigran Aivazian. Dec 2000.
  */
 
 #include <linux/config.h>
@@ -58,6 +59,12 @@
 /* this is initialized in init/main.c */
 kdev_t ROOT_DEV;
 
+/* this can be set at boot time, e.g. rootfs=ext2 
+ * if set to invalid value or if read_super() fails on the specified
+ * filesystem type then mount_root() will go through all registered filesystems.
+ */
+static char rootfs[32] __initdata = "";
+
 int nr_super_blocks;
 int max_super_blocks = NR_SUPER;
 LIST_HEAD(super_blocks);
@@ -78,6 +85,17 @@
 static struct file_system_type *file_systems;
 static rwlock_t file_systems_lock = RW_LOCK_UNLOCKED;
 
+static int __init rootfs_setup(char *line)
+{
+	int n = strlen(line) + 1;
+
+	if (n > 1 && n < 32)
+		strncpy(rootfs, line, n);
+	return 1;
+}
+
+__setup("rootfs=", rootfs_setup);
+
 /* WARNING: This can be used only if we _already_ own a reference */
 static void get_filesystem(struct file_system_type *fs)
 {
@@ -1579,6 +1597,16 @@
 		goto mount_it;
 	}
 
+	if (*rootfs) {
+		fs_type = get_fs_type(rootfs);
+		if (fs_type) {
+  			sb = read_super(ROOT_DEV,bdev,fs_type,root_mountflags,NULL,1);
+			if (sb)
+				goto mount_it;
+		} 
+		/* don't try others if type given explicitly, same behaviour as mount(8) */
+		goto fail;
+	}
 	read_lock(&file_systems_lock);
 	for (fs_type = file_systems ; fs_type ; fs_type = fs_type->next) {
   		if (!(fs_type->fs_flags & FS_REQUIRES_DEV))
@@ -1593,6 +1621,7 @@
 		put_filesystem(fs_type);
 	}
 	read_unlock(&file_systems_lock);
+fail:
 	panic("VFS: Unable to mount root fs on %s", kdevname(ROOT_DEV));
 
 mount_it:




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