Re: [PATCH] [7/16] POISON: Add basic support for poisoned pages in fault handler

Hidehiro Kawai
2009-05-26T12:57:48Z

Andi Kleen wrote:

> - Add a new VM_FAULT_POISON error code to handle_mm_fault. Right now
> architectures have to explicitely enable poison page support, so
> this is forward compatible to all architectures. They only need
> to add it when they enable poison page support.
> - Add poison page handling in swap in fault code
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
>
> ---
> include/linux/mm.h | 3 ++-
> mm/memory.c | 17 ++++++++++++++---
> 2 files changed, 16 insertions(+), 4 deletions(-)
>
> Index: linux/mm/memory.c
> ===================================================================
> --- linux.orig/mm/memory.c 2009-04-07 16:39:24.000000000 +0200
> +++ linux/mm/memory.c 2009-04-07 16:43:06.000000000 +0200
> @@ -1315,7 +1315,8 @@
> if (ret & VM_FAULT_ERROR) {
> if (ret & VM_FAULT_OOM)
> return i ? i : -ENOMEM;
> - else if (ret & VM_FAULT_SIGBUS)
> + if (ret &
> + (VM_FAULT_POISON|VM_FAULT_SIGBUS))
> return i ? i : -EFAULT;
> BUG();
> }
> @@ -2426,8 +2427,15 @@
> goto out;
>
> entry = pte_to_swp_entry(orig_pte);
> - if (is_migration_entry(entry)) {
> - migration_entry_wait(mm, pmd, address);
> + if (unlikely(non_swap_entry(entry))) {
> + if (is_migration_entry(entry)) {
> + migration_entry_wait(mm, pmd, address);
> + } else if (is_poison_entry(entry)) {
> + ret = VM_FAULT_POISON;
> + } else {
> + print_bad_pte(vma, address, pte, NULL);
> + ret = VM_FAULT_OOM;
> + }
> goto out;
> }
> delayacct_set_flag(DELAYACCT_PF_SWAPIN);
> @@ -2451,6 +2459,9 @@
> /* Had to read the page from swap area: Major fault */
> ret = VM_FAULT_MAJOR;
> count_vm_event(PGMAJFAULT);
> + } else if (PagePoison(page)) {
> + ret = VM_FAULT_POISON;

delayacct_clear_flag(DELAYACCT_PF_SWAPIN) would be needed here.

> + goto out;
> }
>
> lock_page(page);

Regards,
--
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center