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mm: always compile in pte markers 

Patch series "mm: Use pte marker for swapin errors".

This series uses the pte marker to replace the swapin error swap entry,
then we save one more swap entry slot for swap devices.  A new pte marker
bit is defined.


This patch (of 2):

The PTE markers code is tiny and now it's enabled for most of the
distributions.  It's fine to keep it as-is, but to make a broader use of
it (e.g.  replacing read error swap entry) it needs to be there always
otherwise we need special code path to take care of !PTE_MARKER case.

It'll be easier just make pte marker always exist.  Use this chance to
extend its usage to anonymous too by simply touching up some of the old
comments, because it'll be used for anonymous pages in the follow up
patches.

Link: https://lkml.kernel.org/r/20221030214151.402274-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20221030214151.402274-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Huang Ying <ying.huang@intel.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2022-10-30 17:41:50 -04:00 committed by Andrew Morton
parent f15be1b8d4
commit ca92ea3dc5
4 changed files with 6 additions and 49 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/linux/swap.h
View File

@ -60,17 +60,13 @@ static inline int current_is_kswapd(void)
SWP_MIGRATION_NUM + SWP_DEVICE_NUM + \
SWP_PTE_MARKER_NUM)
/*
* PTE markers are used to persist information onto PTEs that are mapped with
* file-backed memories. As its name "PTE" hints, it should only be applied to
* the leaves of pgtables.
* PTE markers are used to persist information onto PTEs that otherwise
* should be a none pte. As its name "PTE" hints, it should only be
* applied to the leaves of pgtables.
*/
#ifdef CONFIG_PTE_MARKER
#define SWP_PTE_MARKER_NUM 1
#define SWP_PTE_MARKER (MAX_SWAPFILES + SWP_HWPOISON_NUM + \
SWP_MIGRATION_NUM + SWP_DEVICE_NUM)
#else
#define SWP_PTE_MARKER_NUM 0
#endif
/*
* Unaddressable device memory support. See include/linux/hmm.h and

31
include/linux/swapops.h
View File

@ -412,8 +412,6 @@ typedef unsigned long pte_marker;
#define PTE_MARKER_UFFD_WP BIT(0)
#define PTE_MARKER_MASK (PTE_MARKER_UFFD_WP)
#ifdef CONFIG_PTE_MARKER
static inline swp_entry_t make_pte_marker_entry(pte_marker marker)
{
return swp_entry(SWP_PTE_MARKER, marker);
@ -434,32 +432,6 @@ static inline bool is_pte_marker(pte_t pte)
return is_swap_pte(pte) && is_pte_marker_entry(pte_to_swp_entry(pte));
}
#else /* CONFIG_PTE_MARKER */
static inline swp_entry_t make_pte_marker_entry(pte_marker marker)
{
/* This should never be called if !CONFIG_PTE_MARKER */
WARN_ON_ONCE(1);
return swp_entry(0, 0);
}
static inline bool is_pte_marker_entry(swp_entry_t entry)
{
return false;
}
static inline pte_marker pte_marker_get(swp_entry_t entry)
{
return 0;
}
static inline bool is_pte_marker(pte_t pte)
{
return false;
}
#endif /* CONFIG_PTE_MARKER */
static inline pte_t make_pte_marker(pte_marker marker)
{
return swp_entry_to_pte(make_pte_marker_entry(marker));
@ -477,9 +449,6 @@ static inline pte_t make_pte_marker(pte_marker marker)
* memory, kernel-only memory (including when the system is during-boot),
* non-ram based generic file-system. It's fine to be used even there, but the
* extra pte marker check will be pure overhead.
*
* For systems configured with !CONFIG_PTE_MARKER this will be automatically
* optimized to pte_none().
*/
static inline int pte_none_mostly(pte_t pte)
{

7
mm/Kconfig
View File

@ -1107,17 +1107,10 @@ config HAVE_ARCH_USERFAULTFD_MINOR
help
Arch has userfaultfd minor fault support
config PTE_MARKER
bool
help
Allows to create marker PTEs for file-backed memory.
config PTE_MARKER_UFFD_WP
bool "Userfaultfd write protection support for shmem/hugetlbfs"
default y
depends on HAVE_ARCH_USERFAULTFD_WP
select PTE_MARKER
help
Allows to create marker PTEs for userfaultfd write protection

7
mm/memory.c
View File

@ -3662,11 +3662,10 @@ static vm_fault_t handle_pte_marker(struct vm_fault *vmf)
unsigned long marker = pte_marker_get(entry);
/*
* PTE markers should always be with file-backed memories, and the
* marker should never be empty. If anything weird happened, the best
* thing to do is to kill the process along with its mm.
* PTE markers should never be empty. If anything weird happened,
* the best thing to do is to kill the process along with its mm.
*/
if (WARN_ON_ONCE(vma_is_anonymous(vmf->vma) || !marker))
if (WARN_ON_ONCE(!marker))
return VM_FAULT_SIGBUS;
if (pte_marker_entry_uffd_wp(entry))