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Subject[final] Re: [patch-2.4.0-test13-pre3] rootfs (2nd attempt)
On Mon, 18 Dec 2000, Andreas Dilger wrote:
> If I could add one thing here (we have had a 2.2 patch like this for testing
> with ext3) - if you specify the rootfstype parameter don't use the "quiet"
> option to read_super, so you know why it couldn't mount a specific filesystem
> as root, and/or print rootfs type in the panic message.

Agree completely.

Here is the hopefully final version. Sorry, Linus, I thought the first
version was final :) Looks like I have missed a couple of very useful
things... Thanks to all who commented!

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 15:03:44 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 panic
+ */
+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,0);
+ 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 %s on %s", *rootfs ? rootfs : "fs", kdevname(ROOT_DEV));

mount_it:
-
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