Re: suspect list_empty( {NULL, NULL} )

[Andrew Morton]

Zach Brown wrote:
> 
> A cute list_head debugging patch seems to have found strange list_entry
> use in vmscan.c in stock 2.5.39.
> 
> page_mapping_inuse:
> 
>         if (!list_empty(&mapping->i_mmap) || !list_empty(&mapping->i_mmap_shared))
> 
> ...
> (gdb) print *mapping
> $22 = {host = 0xc03b6e00

That's swapper_space.

--- 2.5.39/mm/swap_state.c~swapper_space-state	Sat Sep 28 18:30:45 2002
+++ 2.5.39-akpm/mm/swap_state.c	Sat Sep 28 18:31:26 2002
@@ -43,6 +43,8 @@ struct address_space swapper_space = {
 	.a_ops			= &swap_aops,
 	.backing_dev_info	= &swap_backing_dev_info,
 	.i_shared_lock		= SPIN_LOCK_UNLOCKED,
+	.i_mmap			= LIST_HEAD_INIT(swapper_space.i_mmap),
+	.i_mmap_shared		= LIST_HEAD_INIT(swapper_space.i_mmap_shared),
 	.private_lock		= SPIN_LOCK_UNLOCKED,
 	.private_list		= LIST_HEAD_INIT(swapper_space.private_list),
 };

.