Commit fd57a1c4 authored by David Hildenbrand's avatar David Hildenbrand Committed by Kefeng Wang
Browse files

mm/mmu_gather: define ENCODED_PAGE_FLAG_DELAY_RMAP 

mainline inclusion
from mainline-v6.9-rc1
commit da510964c095cb5e070800ef38752c453d2aa71d
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9CHB4
CVE: NA

-------------------------------------------------

Nowadays, encoded pages are only used in mmu_gather handling.  Let's
update the documentation, and define ENCODED_PAGE_BIT_DELAY_RMAP.  While
at it, rename ENCODE_PAGE_BITS to ENCODED_PAGE_BITS.

If encoded page pointers would ever be used in other context again, we'd
likely want to change the defines to reflect their context (e.g.,
ENCODED_PAGE_FLAG_MMU_GATHER_DELAY_RMAP).  For now, let's keep it simple.

This is a preparation for using the remaining spare bit to indicate that
the next item in an array of encoded pages is a "nr_pages" argument and
not an encoded page.

Link: https://lkml.kernel.org/r/20240214204435.167852-7-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
(cherry picked from commit da510964c095cb5e070800ef38752c453d2aa71d)
Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
parent 62845e58

include/linux/mm_types.h

+11 −6
Original line number Diff line number Diff line
@@ -224,8 +224,8 @@ struct page { 
 *

 * An 'encoded_page' pointer is a pointer to a regular 'struct page', but

 * with the low bits of the pointer indicating extra context-dependent

 * information. Not super-common, but happens in mmu_gather and mlock

 * handling, and this acts as a type system check on that use.

 * information. Only used in mmu_gather handling, and this acts as a type

 * system check on that use.

 *

 * We only really have two guaranteed bits in general, although you could

 * play with 'struct page' alignment (see CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
@@ -234,21 +234,26 @@ struct page { 
 * Use the supplied helper functions to endcode/decode the pointer and bits.

 */

struct encoded_page;

#define ENCODE_PAGE_BITS 3ul



#define ENCODED_PAGE_BITS			3ul



/* Perform rmap removal after we have flushed the TLB. */

#define ENCODED_PAGE_BIT_DELAY_RMAP		1ul



static __always_inline struct encoded_page *encode_page(struct page *page, unsigned long flags)

{

	BUILD_BUG_ON(flags > ENCODE_PAGE_BITS);

	BUILD_BUG_ON(flags > ENCODED_PAGE_BITS);

	return (struct encoded_page *)(flags | (unsigned long)page);

}



static inline unsigned long encoded_page_flags(struct encoded_page *page)

{

	return ENCODE_PAGE_BITS & (unsigned long)page;

	return ENCODED_PAGE_BITS & (unsigned long)page;

}



static inline struct page *encoded_page_ptr(struct encoded_page *page)

{

	return (struct page *)(~ENCODE_PAGE_BITS & (unsigned long)page);

	return (struct page *)(~ENCODED_PAGE_BITS & (unsigned long)page);

}



/*

mm/mmu_gather.c

+3 −2
Original line number Diff line number Diff line
@@ -53,7 +53,7 @@ static void tlb_flush_rmap_batch(struct mmu_gather_batch *batch, struct vm_area_ 
	for (int i = 0; i < batch->nr; i++) {

		struct encoded_page *enc = batch->encoded_pages[i];



		if (encoded_page_flags(enc)) {

		if (encoded_page_flags(enc) & ENCODED_PAGE_BIT_DELAY_RMAP) {

			struct page *page = encoded_page_ptr(enc);

			folio_remove_rmap_pte(page_folio(page), page, vma);

		}
@@ -119,6 +119,7 @@ static void tlb_batch_list_free(struct mmu_gather *tlb) 
bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,

		bool delay_rmap, int page_size)

{

	int flags = delay_rmap ? ENCODED_PAGE_BIT_DELAY_RMAP : 0;

	struct mmu_gather_batch *batch;



	VM_BUG_ON(!tlb->end);
@@ -132,7 +133,7 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, 
	 * Add the page and check if we are full. If so

	 * force a flush.

	 */

	batch->encoded_pages[batch->nr++] = encode_page(page, delay_rmap);

	batch->encoded_pages[batch->nr++] = encode_page(page, flags);

	if (batch->nr == batch->max) {

		if (!tlb_next_batch(tlb))

			return true;