[PATCH] root mount failure: emit filesystems attempted

When we fail to mount from a valid root device list out the filesystems we
have tried to mount it with.  This gives the user vital diagnostics as to
what is missing from their kernel.

For example in the fragment below the kernel does not have CRAMFS compiled
into the kernel and yet appears to recognise it at the RAMDISK detect
stage.  Later the mount fails as we don't have the filesystem.

  RAMDISK: cramfs filesystem found at block 0
  RAMDISK: Loading 1604KiB [1 disk] into ram disk... done.
  XFS: bad magic number
  XFS: SB validate failed
  No filesystem could mount root, tried: reiserfs ext3 ext2 msdos vfat
    iso9660 jfs xfs
  Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(8,1)
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

init/do_mounts.c

@@ -310,6 +310,11 @@ void __init mount_block_root(char *name, int flags)
 
 		panic("VFS: Unable to mount root fs on %s", b);
 	}
+
+	printk("No filesystem could mount root, tried: ");
+	for (p = fs_names; *p; p += strlen(p)+1)
+		printk(" %s", p);
+	printk("\n");
 	panic("VFS: Unable to mount root fs on %s", __bdevname(ROOT_DEV, b));
 out:
 	putname(fs_names);