Re: [PATCH] x86: endless page faults in mount_block_root for Linux 2.6

Pekka Enberg
2008-04-29T15:14:54Z

On Tue, Apr 29, 2008 at 5:33 PM, Ingo Molnar <mingo@elte.hu> wrote:
> btw., i have a kmemcheck-reported bug fixed in this same area with the
> patch below. I dont remember the details anymore, but the root mount
> code did something really, really weird here.
>
> Subject: init: root mount fix
> From: Ingo Molnar <mingo@elte.hu>
> Date: Tue Apr 29 16:31:50 CEST 2008
>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---
> init/do_mounts.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> Index: linux/init/do_mounts.c
> ===================================================================
> --- linux.orig/init/do_mounts.c
> +++ linux/init/do_mounts.c
> @@ -201,9 +201,13 @@ static int __init do_mount_root(char *na
> return 0;
> }
>
> +#if PAGE_SIZE < PATH_MAX
> +# error increase the fs_names allocation size here
> +#endif
>
> +
> void __init mount_block_root(char *name, int flags)
> {
> - char *fs_names = __getname();
> + char *fs_names = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
>
> char *p;
> #ifdef CONFIG_BLOCK
> char b[BDEVNAME_SIZE];
> @@ -251,7 +255,7 @@ retry:
>
> #endif
> panic("VFS: Unable to mount root fs on %s", b);
> out:
> - putname(fs_names);
> + free_pages((unsigned long)fs_names, 1);
> }
>
> #ifdef CONFIG_ROOT_NFS

It could have been a bug in early kmemcheck too. We don't check memory
allocated with the page allocator, only slab, so this shouldn't
trigger anything.