linux-kernel - [PATCH 3/4] mm: mmu_gather: prepare to gather encoded page pointers with flags

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Date:   Tue,  8 Nov 2022 11:41:38 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Hugh Dickins <hughd@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 3/4] mm: mmu_gather: prepare to gather encoded page pointers with flags

This is purely a preparatory patch that makes all the data structures
ready for encoding flags with the mmu_gather page pointers.

The code currently always sets the flag to zero and doesn't use it yet,
but now it's tracking the type state along.  The next step will be to
actually start using it.

Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
---
 include/asm-generic/tlb.h |  2 +-
 include/linux/swap.h      |  2 +-
 mm/mmu_gather.c           |  4 ++--
 mm/swap_state.c           | 11 ++++-------
 4 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 492dce43236e..faca23e87278 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -242,7 +242,7 @@ struct mmu_gather_batch {
 	struct mmu_gather_batch	*next;
 	unsigned int		nr;
 	unsigned int		max;
-	struct page		*pages[];
+	struct encoded_page	*encoded_pages[];
 };
 
 #define MAX_GATHER_BATCH	\
diff --git a/include/linux/swap.h b/include/linux/swap.h
index a18cf4b7c724..40e418e3461b 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -470,7 +470,7 @@ static inline unsigned long total_swapcache_pages(void)
 
 extern void free_swap_cache(struct page *page);
 extern void free_page_and_swap_cache(struct page *);
-extern void free_pages_and_swap_cache(struct page **, int);
+extern void free_pages_and_swap_cache(struct encoded_page **, int);
 /* linux/mm/swapfile.c */
 extern atomic_long_t nr_swap_pages;
 extern long total_swap_pages;
diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
index add4244e5790..57b7850c1b5e 100644
--- a/mm/mmu_gather.c
+++ b/mm/mmu_gather.c
@@ -48,7 +48,7 @@ static void tlb_batch_pages_flush(struct mmu_gather *tlb)
 	struct mmu_gather_batch *batch;
 
 	for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
-		struct page **pages = batch->pages;
+		struct encoded_page **pages = batch->encoded_pages;
 
 		do {
 			/*
@@ -92,7 +92,7 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_
 	 * Add the page and check if we are full. If so
 	 * force a flush.
 	 */
-	batch->pages[batch->nr++] = page;
+	batch->encoded_pages[batch->nr++] = encode_page(page, 0);
 	if (batch->nr == batch->max) {
 		if (!tlb_next_batch(tlb))
 			return true;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 438d0676c5be..8bf08c313872 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -303,15 +303,12 @@ void free_page_and_swap_cache(struct page *page)
  * Passed an array of pages, drop them all from swapcache and then release
  * them.  They are removed from the LRU and freed if this is their last use.
  */
-void free_pages_and_swap_cache(struct page **pages, int nr)
+void free_pages_and_swap_cache(struct encoded_page **pages, int nr)
 {
-	struct page **pagep = pages;
-	int i;
-
 	lru_add_drain();
-	for (i = 0; i < nr; i++)
-		free_swap_cache(pagep[i]);
-	release_pages(pagep, nr);
+	for (int i = 0; i < nr; i++)
+		free_swap_cache(encoded_page_ptr(pages[i]));
+	release_pages(pages, nr);
 }
 
 static inline bool swap_use_vma_readahead(void)
-- 
2.38.1.284.gfd9468d787