On Tue, Dec 16, 2014 at 12:56:15PM +0000, Al Viro wrote:
> On Tue, Dec 16, 2014 at 03:55:37AM -0800, Jeremiah Mahler wrote:
> > all,
> >
> > The wireless network interface has become inoperative when running
> > linux-next 20141216 on a Lenovo Carbon X1. It is completely
> > non-existent and `ip addr` doesn't show it. A bisect has found that
> > the bug was introduced by the following commit.
>
> Very interesting. What userland are you running? I take it, the root
> filesystem is mounted and system boot except for that interface not
> coming up, right?
>
> Your card is normally handled by what, iwlwifi? What happens upon
> modprobe iwlwifi (or whatever module you see loaded on the normal
> boot)? Another interesting question is whether it manages to load
> the firmware... What happens if you boot with debug in kernel command
> line, with working and with non-working kernels resp.?
Hmm... OK, I think I see what might be going on. On the testbox here
I've got pivot_root(2) done from /init on initramfs. And that triggers
chroot_fs_refs(), which switches init_fs.{root,pwd} to the final rootfs.
In your case it apparently isn't triggered (different userland or setup,
perhaps) and init_fs is left behind on initramfs. With some files
(firmware?) not being there... Could you check if the following kludge
helps? It's not intended as a solution, I just want to verify that guess
about the mechanism of the problem...
diff --git a/init/main.c b/init/main.c
index 3a169a2..36c29d6 100644
--- a/init/main.c
+++ b/init/main.c
@@ -80,6 +80,8 @@
#include <linux/list.h>
#include <linux/proc_ns.h>
#include <linux/fs_struct.h>
+#include "../fs/internal.h" // HACK
+#include <linux/init_task.h> // HACK
#include <asm/io.h>
#include <asm/bugs.h>
@@ -1024,6 +1026,15 @@ static noinline void __init kernel_init_freeable(void)
if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
ramdisk_execute_command = NULL;
prepare_namespace();
+ {
+ /* HACK */
+ struct path old, new;
+ get_fs_root(current->fs, &new);
+ get_fs_root(&init_fs, &old);
+ chroot_fs_refs(&old, &new);
+ path_put(&old);
+ path_put(&new);
+ }
}
/*
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