[PATCH 00/21] Folio patches for 5.19

[PATCH 00/21] Folio patches for 5.19

[Matthew Wilcox (Oracle)]

Andrew, do you want to include these patches in -mm?

 - Finish the conversion from alloc_pages_vma() to vma_alloc_folio()
 - Finish converting shrink_page_list() to folios
 - Start converting shmem from pages to folios (alas, not finished,
   I have simply run out of time with all the debugging/fixing needed
   for 5.18)

Matthew Wilcox (Oracle) (21):
  shmem: Convert shmem_alloc_hugepage() to use vma_alloc_folio()
  mm/huge_memory: Convert do_huge_pmd_anonymous_page() to use 
    vma_alloc_folio()
  mm: Remove alloc_pages_vma()
  vmscan: Use folio_mapped() in shrink_page_list()
  vmscan: Convert the writeback handling in shrink_page_list() to folios
  swap: Turn get_swap_page() into folio_alloc_swap()
  swap: Convert add_to_swap() to take a folio
  vmscan: Convert dirty page handling to folios
  vmscan: Convert page buffer handling to use folios
  vmscan: Convert lazy freeing to folios
  vmscan: Move initialisation of mapping down
  vmscan: Convert the activate_locked portion of shrink_page_list to
    folios
  vmscan: Remove remaining uses of page in shrink_page_list
  mm/shmem: Use a folio in shmem_unused_huge_shrink
  mm/swap: Add folio_throttle_swaprate
  mm/shmem: Convert shmem_add_to_page_cache to take a folio
  mm/shmem: Turn shmem_should_replace_page into
    shmem_should_replace_folio
  mm/shmem: Turn shmem_alloc_page() into shmem_alloc_folio()
  mm/shmem: Convert shmem_alloc_and_acct_page to use a folio
  mm/shmem: Convert shmem_getpage_gfp to use a folio
  mm/shmem: Convert shmem_swapin_page() to shmem_swapin_folio()

 arch/arm64/include/asm/pgtable.h |   6 +-
 include/linux/gfp.h              |  18 +-
 include/linux/memcontrol.h       |  14 ++
 include/linux/pgtable.h          |   2 +-
 include/linux/swap.h             |  23 ++-
 mm/huge_memory.c                 |   9 +-
 mm/memcontrol.c                  |  16 +-
 mm/mempolicy.c                   |  51 +++--
 mm/shmem.c                       | 314 ++++++++++++++---------------
 mm/swap_slots.c                  |  14 +-
 mm/swap_state.c                  |  48 ++---
 mm/swapfile.c                    |  17 +-
 mm/vmscan.c                      | 326 ++++++++++++++++---------------
 13 files changed, 437 insertions(+), 421 deletions(-)

-- 
2.34.1

[PATCH 01/21] shmem: Convert shmem_alloc_hugepage() to use vma_alloc_folio()

[Matthew Wilcox (Oracle)]

For now, return the head page of the folio, but remove use of the
old alloc_pages_vma() API.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/shmem.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 4b2fea33158e..c89394221a7e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1527,7 +1527,7 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 	struct vm_area_struct pvma;
 	struct address_space *mapping = info->vfs_inode.i_mapping;
 	pgoff_t hindex;
-	struct page *page;
+	struct folio *folio;
 
 	hindex = round_down(index, HPAGE_PMD_NR);
 	if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
@@ -1535,13 +1535,11 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 		return NULL;
 
 	shmem_pseudo_vma_init(&pvma, info, hindex);
-	page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER, &pvma, 0, true);
+	folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, &pvma, 0, true);
 	shmem_pseudo_vma_destroy(&pvma);
-	if (page)
-		prep_transhuge_page(page);
-	else
+	if (!folio)
 		count_vm_event(THP_FILE_FALLBACK);
-	return page;
+	return &folio->page;
 }
 
 static struct page *shmem_alloc_page(gfp_t gfp,
-- 
2.34.1

[PATCH 02/21] mm/huge_memory: Convert do_huge_pmd_anonymous_page() to use vma_alloc_folio()

[Matthew Wilcox (Oracle)]

Remove the use of this old API, eliminating a call to prep_transhuge_page().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/huge_memory.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c468fee595ff..caf0e7d27337 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -725,7 +725,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	gfp_t gfp;
-	struct page *page;
+	struct folio *folio;
 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 
 	if (!transhuge_vma_suitable(vma, haddr))
@@ -774,13 +774,12 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 		return ret;
 	}
 	gfp = vma_thp_gfp_mask(vma);
-	page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
-	if (unlikely(!page)) {
+	folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, vma, haddr, true);
+	if (unlikely(!folio)) {
 		count_vm_event(THP_FAULT_FALLBACK);
 		return VM_FAULT_FALLBACK;
 	}
-	prep_transhuge_page(page);
-	return __do_huge_pmd_anonymous_page(vmf, page, gfp);
+	return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
 }
 
 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
-- 
2.34.1

[PATCH 03/21] mm: Remove alloc_pages_vma()

[Matthew Wilcox (Oracle)]

All callers have now been converted to use vma_alloc_folio(), so
convert the body of alloc_pages_vma() to allocate folios instead.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/gfp.h | 18 +++++++---------
 mm/mempolicy.c      | 51 ++++++++++++++++++++++-----------------------
 2 files changed, 32 insertions(+), 37 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 3e3d36fc2109..2a08a3c4ba95 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -613,13 +613,8 @@ static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
 #ifdef CONFIG_NUMA
 struct page *alloc_pages(gfp_t gfp, unsigned int order);
 struct folio *folio_alloc(gfp_t gfp, unsigned order);
-struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
-			struct vm_area_struct *vma, unsigned long addr,
-			bool hugepage);
 struct folio *vma_alloc_folio(gfp_t gfp, int order, struct vm_area_struct *vma,
 		unsigned long addr, bool hugepage);
-#define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
-	alloc_pages_vma(gfp_mask, order, vma, addr, true)
 #else
 static inline struct page *alloc_pages(gfp_t gfp_mask, unsigned int order)
 {
@@ -629,16 +624,17 @@ static inline struct folio *folio_alloc(gfp_t gfp, unsigned int order)
 {
 	return __folio_alloc_node(gfp, order, numa_node_id());
 }
-#define alloc_pages_vma(gfp_mask, order, vma, addr, hugepage) \
-	alloc_pages(gfp_mask, order)
 #define vma_alloc_folio(gfp, order, vma, addr, hugepage)		\
 	folio_alloc(gfp, order)
-#define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
-	alloc_pages(gfp_mask, order)
 #endif
 #define alloc_page(gfp_mask) alloc_pages(gfp_mask, 0)
-#define alloc_page_vma(gfp_mask, vma, addr)			\
-	alloc_pages_vma(gfp_mask, 0, vma, addr, false)
+static inline struct page *alloc_page_vma(gfp_t gfp,
+		struct vm_area_struct *vma, unsigned long addr)
+{
+	struct folio *folio = vma_alloc_folio(gfp, 0, vma, addr, false);
+
+	return &folio->page;
+}
 
 extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
 extern unsigned long get_zeroed_page(gfp_t gfp_mask);
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 8c74107a2b15..174efbee1cb5 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2135,44 +2135,55 @@ static struct page *alloc_pages_preferred_many(gfp_t gfp, unsigned int order,
 }
 
 /**
- * alloc_pages_vma - Allocate a page for a VMA.
+ * vma_alloc_folio - Allocate a folio for a VMA.
  * @gfp: GFP flags.
- * @order: Order of the GFP allocation.
+ * @order: Order of the folio.
  * @vma: Pointer to VMA or NULL if not available.
  * @addr: Virtual address of the allocation.  Must be inside @vma.
  * @hugepage: For hugepages try only the preferred node if possible.
  *
- * Allocate a page for a specific address in @vma, using the appropriate
+ * Allocate a folio for a specific address in @vma, using the appropriate
  * NUMA policy.  When @vma is not NULL the caller must hold the mmap_lock
  * of the mm_struct of the VMA to prevent it from going away.  Should be
- * used for all allocations for pages that will be mapped into user space.
+ * used for all allocations for folios that will be mapped into user space.
  *
- * Return: The page on success or NULL if allocation fails.
+ * Return: The folio on success or NULL if allocation fails.
  */
-struct page *alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
+struct folio *vma_alloc_folio(gfp_t gfp, int order, struct vm_area_struct *vma,
 		unsigned long addr, bool hugepage)
 {
 	struct mempolicy *pol;
 	int node = numa_node_id();
-	struct page *page;
+	struct folio *folio;
 	int preferred_nid;
 	nodemask_t *nmask;
 
 	pol = get_vma_policy(vma, addr);
 
 	if (pol->mode == MPOL_INTERLEAVE) {
+		struct page *page;
 		unsigned nid;
 
 		nid = interleave_nid(pol, vma, addr, PAGE_SHIFT + order);
 		mpol_cond_put(pol);
+		gfp |= __GFP_COMP;
 		page = alloc_page_interleave(gfp, order, nid);
+		if (page && order > 1)
+			prep_transhuge_page(page);
+		folio = (struct folio *)page;
 		goto out;
 	}
 
 	if (pol->mode == MPOL_PREFERRED_MANY) {
+		struct page *page;
+
 		node = policy_node(gfp, pol, node);
+		gfp |= __GFP_COMP;
 		page = alloc_pages_preferred_many(gfp, order, node, pol);
 		mpol_cond_put(pol);
+		if (page && order > 1)
+			prep_transhuge_page(page);
+		folio = (struct folio *)page;
 		goto out;
 	}
 
@@ -2199,8 +2210,8 @@ struct page *alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 			 * First, try to allocate THP only on local node, but
 			 * don't reclaim unnecessarily, just compact.
 			 */
-			page = __alloc_pages_node(hpage_node,
-				gfp | __GFP_THISNODE | __GFP_NORETRY, order);
+			folio = __folio_alloc_node(gfp | __GFP_THISNODE |
+					__GFP_NORETRY, order, hpage_node);
 
 			/*
 			 * If hugepage allocations are configured to always
@@ -2208,8 +2219,9 @@ struct page *alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 			 * to prefer hugepage backing, retry allowing remote
 			 * memory with both reclaim and compact as well.
 			 */
-			if (!page && (gfp & __GFP_DIRECT_RECLAIM))
-				page = __alloc_pages(gfp, order, hpage_node, nmask);
+			if (!folio && (gfp & __GFP_DIRECT_RECLAIM))
+				folio = __folio_alloc(gfp, order, hpage_node,
+						      nmask);
 
 			goto out;
 		}
@@ -2217,25 +2229,12 @@ struct page *alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 
 	nmask = policy_nodemask(gfp, pol);
 	preferred_nid = policy_node(gfp, pol, node);
-	page = __alloc_pages(gfp, order, preferred_nid, nmask);
+	folio = __folio_alloc(gfp, order, preferred_nid, nmask);
 	mpol_cond_put(pol);
 out:
-	return page;
-}
-EXPORT_SYMBOL(alloc_pages_vma);
-
-struct folio *vma_alloc_folio(gfp_t gfp, int order, struct vm_area_struct *vma,
-		unsigned long addr, bool hugepage)
-{
-	struct folio *folio;
-
-	folio = (struct folio *)alloc_pages_vma(gfp, order, vma, addr,
-			hugepage);
-	if (folio && order > 1)
-		prep_transhuge_page(&folio->page);
-
 	return folio;
 }
+EXPORT_SYMBOL(vma_alloc_folio);
 
 /**
  * alloc_pages - Allocate pages.
-- 
2.34.1

[PATCH 04/21] vmscan: Use folio_mapped() in shrink_page_list()

[Matthew Wilcox (Oracle)]

Remove some legacy function calls.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/vmscan.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1678802e03e7..27be6f9b2ba5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1549,7 +1549,7 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		if (unlikely(!page_evictable(page)))
 			goto activate_locked;
 
-		if (!sc->may_unmap && page_mapped(page))
+		if (!sc->may_unmap && folio_mapped(folio))
 			goto keep_locked;
 
 		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
@@ -1743,21 +1743,21 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		}
 
 		/*
-		 * The page is mapped into the page tables of one or more
+		 * The folio is mapped into the page tables of one or more
 		 * processes. Try to unmap it here.
 		 */
-		if (page_mapped(page)) {
+		if (folio_mapped(folio)) {
 			enum ttu_flags flags = TTU_BATCH_FLUSH;
-			bool was_swapbacked = PageSwapBacked(page);
+			bool was_swapbacked = folio_test_swapbacked(folio);
 
-			if (PageTransHuge(page) &&
-					thp_order(page) >= HPAGE_PMD_ORDER)
+			if (folio_test_pmd_mappable(folio))
 				flags |= TTU_SPLIT_HUGE_PMD;
 
 			try_to_unmap(folio, flags);
-			if (page_mapped(page)) {
+			if (folio_mapped(folio)) {
 				stat->nr_unmap_fail += nr_pages;
-				if (!was_swapbacked && PageSwapBacked(page))
+				if (!was_swapbacked &&
+				    folio_test_swapbacked(folio))
 					stat->nr_lazyfree_fail += nr_pages;
 				goto activate_locked;
 			}
-- 
2.34.1

[PATCH 05/21] vmscan: Convert the writeback handling in shrink_page_list() to folios

[Matthew Wilcox (Oracle)]

Slightly more efficient due to fewer calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/vmscan.c | 77 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 41 insertions(+), 36 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 27be6f9b2ba5..19c1bcd886ef 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1578,40 +1578,42 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			stat->nr_congested += nr_pages;
 
 		/*
-		 * If a page at the tail of the LRU is under writeback, there
+		 * If a folio at the tail of the LRU is under writeback, there
 		 * are three cases to consider.
 		 *
-		 * 1) If reclaim is encountering an excessive number of pages
-		 *    under writeback and this page is both under writeback and
-		 *    PageReclaim then it indicates that pages are being queued
-		 *    for IO but are being recycled through the LRU before the
-		 *    IO can complete. Waiting on the page itself risks an
-		 *    indefinite stall if it is impossible to writeback the
-		 *    page due to IO error or disconnected storage so instead
-		 *    note that the LRU is being scanned too quickly and the
-		 *    caller can stall after page list has been processed.
+		 * 1) If reclaim is encountering an excessive number of folios
+		 *    under writeback and this folio is both under
+		 *    writeback and has the reclaim flag set then it
+		 *    indicates that folios are being queued for I/O but
+		 *    are being recycled through the LRU before the I/O
+		 *    can complete. Waiting on the folio itself risks an
+		 *    indefinite stall if it is impossible to writeback
+		 *    the folio due to I/O error or disconnected storage
+		 *    so instead note that the LRU is being scanned too
+		 *    quickly and the caller can stall after the folio
+		 *    list has been processed.
 		 *
-		 * 2) Global or new memcg reclaim encounters a page that is
+		 * 2) Global or new memcg reclaim encounters a folio that is
 		 *    not marked for immediate reclaim, or the caller does not
 		 *    have __GFP_FS (or __GFP_IO if it's simply going to swap,
-		 *    not to fs). In this case mark the page for immediate
+		 *    not to fs). In this case mark the folio for immediate
 		 *    reclaim and continue scanning.
 		 *
 		 *    Require may_enter_fs because we would wait on fs, which
-		 *    may not have submitted IO yet. And the loop driver might
-		 *    enter reclaim, and deadlock if it waits on a page for
+		 *    may not have submitted I/O yet. And the loop driver might
+		 *    enter reclaim, and deadlock if it waits on a folio for
 		 *    which it is needed to do the write (loop masks off
 		 *    __GFP_IO|__GFP_FS for this reason); but more thought
 		 *    would probably show more reasons.
 		 *
-		 * 3) Legacy memcg encounters a page that is already marked
-		 *    PageReclaim. memcg does not have any dirty pages
+		 * 3) Legacy memcg encounters a folio that already has the
+		 *    reclaim flag set. memcg does not have any dirty folio
 		 *    throttling so we could easily OOM just because too many
-		 *    pages are in writeback and there is nothing else to
+		 *    folios are in writeback and there is nothing else to
 		 *    reclaim. Wait for the writeback to complete.
 		 *
-		 * In cases 1) and 2) we activate the pages to get them out of
-		 * the way while we continue scanning for clean pages on the
+		 * In cases 1) and 2) we activate the folios to get them out of
+		 * the way while we continue scanning for clean folios on the
 		 * inactive list and refilling from the active list. The
 		 * observation here is that waiting for disk writes is more
 		 * expensive than potentially causing reloads down the line.
@@ -1619,38 +1621,41 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		 * memory pressure on the cache working set any longer than it
 		 * takes to write them to disk.
 		 */
-		if (PageWriteback(page)) {
+		if (folio_test_writeback(folio)) {
 			/* Case 1 above */
 			if (current_is_kswapd() &&
-			    PageReclaim(page) &&
+			    folio_test_reclaim(folio) &&
 			    test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
 				stat->nr_immediate += nr_pages;
 				goto activate_locked;
 
 			/* Case 2 above */
 			} else if (writeback_throttling_sane(sc) ||
-			    !PageReclaim(page) || !may_enter_fs) {
+			    !folio_test_reclaim(folio) || !may_enter_fs) {
 				/*
-				 * This is slightly racy - end_page_writeback()
-				 * might have just cleared PageReclaim, then
-				 * setting PageReclaim here end up interpreted
-				 * as PageReadahead - but that does not matter
-				 * enough to care.  What we do want is for this
-				 * page to have PageReclaim set next time memcg
-				 * reclaim reaches the tests above, so it will
-				 * then wait_on_page_writeback() to avoid OOM;
-				 * and it's also appropriate in global reclaim.
+				 * This is slightly racy -
+				 * folio_end_writeback() might have just
+				 * cleared the reclaim flag, then setting
+				 * reclaim here ends up interpreted as
+				 * the readahead flag - but that does
+				 * not matter enough to care.  What we
+				 * do want is for this folio to have
+				 * the reclaim flag set next time memcg
+				 * reclaim reaches the tests above, so
+				 * it will then folio_wait_writeback()
+				 * to avoid OOM; and it's also appropriate
+				 * in global reclaim.
 				 */
-				SetPageReclaim(page);
+				folio_set_reclaim(folio);
 				stat->nr_writeback += nr_pages;
 				goto activate_locked;
 
 			/* Case 3 above */
 			} else {
-				unlock_page(page);
-				wait_on_page_writeback(page);
-				/* then go back and try same page again */
-				list_add_tail(&page->lru, page_list);
+				folio_unlock(folio);
+				folio_wait_writeback(folio);
+				/* then go back and try same folio again */
+				list_add_tail(&folio->lru, page_list);
 				continue;
 			}
 		}
-- 
2.34.1

[PATCH 06/21] swap: Turn get_swap_page() into folio_alloc_swap()

[Matthew Wilcox (Oracle)]

This removes an assumption that a large folio is HPAGE_PMD_NR pages
in size.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/swap.h | 13 +++++++------
 mm/memcontrol.c      | 16 ++++++++--------
 mm/shmem.c           |  3 ++-
 mm/swap_slots.c      | 14 +++++++-------
 mm/swap_state.c      |  3 ++-
 mm/swapfile.c        | 17 +++++++++--------
 6 files changed, 35 insertions(+), 31 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 27093b477c5f..147a9a173508 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -494,7 +494,7 @@ static inline long get_nr_swap_pages(void)
 }
 
 extern void si_swapinfo(struct sysinfo *);
-extern swp_entry_t get_swap_page(struct page *page);
+swp_entry_t folio_alloc_swap(struct folio *folio);
 extern void put_swap_page(struct page *page, swp_entry_t entry);
 extern swp_entry_t get_swap_page_of_type(int);
 extern int get_swap_pages(int n, swp_entry_t swp_entries[], int entry_size);
@@ -685,7 +685,7 @@ static inline int try_to_free_swap(struct page *page)
 	return 0;
 }
 
-static inline swp_entry_t get_swap_page(struct page *page)
+static inline swp_entry_t folio_alloc_swap(struct folio *folio)
 {
 	swp_entry_t entry;
 	entry.val = 0;
@@ -739,12 +739,13 @@ static inline void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
 
 #ifdef CONFIG_MEMCG_SWAP
 void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry);
-extern int __mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
-static inline int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry);
+static inline int mem_cgroup_try_charge_swap(struct folio *folio,
+		swp_entry_t entry)
 {
 	if (mem_cgroup_disabled())
 		return 0;
-	return __mem_cgroup_try_charge_swap(page, entry);
+	return __mem_cgroup_try_charge_swap(folio, entry);
 }
 
 extern void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
@@ -762,7 +763,7 @@ static inline void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 {
 }
 
-static inline int mem_cgroup_try_charge_swap(struct page *page,
+static inline int mem_cgroup_try_charge_swap(struct folio *folio,
 					     swp_entry_t entry)
 {
 	return 0;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 598fece89e2b..985eff804004 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7125,17 +7125,17 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 }
 
 /**
- * __mem_cgroup_try_charge_swap - try charging swap space for a page
- * @page: page being added to swap
+ * __mem_cgroup_try_charge_swap - try charging swap space for a folio
+ * @folio: folio being added to swap
  * @entry: swap entry to charge
  *
- * Try to charge @page's memcg for the swap space at @entry.
+ * Try to charge @folio's memcg for the swap space at @entry.
  *
  * Returns 0 on success, -ENOMEM on failure.
  */
-int __mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
 {
-	unsigned int nr_pages = thp_nr_pages(page);
+	unsigned int nr_pages = folio_nr_pages(folio);
 	struct page_counter *counter;
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
@@ -7143,9 +7143,9 @@ int __mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return 0;
 
-	memcg = page_memcg(page);
+	memcg = folio_memcg(folio);
 
-	VM_WARN_ON_ONCE_PAGE(!memcg, page);
+	VM_WARN_ON_ONCE_FOLIO(!memcg, folio);
 	if (!memcg)
 		return 0;
 
@@ -7168,7 +7168,7 @@ int __mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 	if (nr_pages > 1)
 		mem_cgroup_id_get_many(memcg, nr_pages - 1);
 	oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg), nr_pages);
-	VM_BUG_ON_PAGE(oldid, page);
+	VM_BUG_ON_FOLIO(oldid, folio);
 	mod_memcg_state(memcg, MEMCG_SWAP, nr_pages);
 
 	return 0;
diff --git a/mm/shmem.c b/mm/shmem.c
index c89394221a7e..85c23696efc6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1312,6 +1312,7 @@ int shmem_unuse(unsigned int type)
  */
 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 {
+	struct folio *folio = page_folio(page);
 	struct shmem_inode_info *info;
 	struct address_space *mapping;
 	struct inode *inode;
@@ -1385,7 +1386,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 		SetPageUptodate(page);
 	}
 
-	swap = get_swap_page(page);
+	swap = folio_alloc_swap(folio);
 	if (!swap.val)
 		goto redirty;
 
diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index 2b5531840583..0218ec1cd24c 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -117,7 +117,7 @@ static int alloc_swap_slot_cache(unsigned int cpu)
 
 	/*
 	 * Do allocation outside swap_slots_cache_mutex
-	 * as kvzalloc could trigger reclaim and get_swap_page,
+	 * as kvzalloc could trigger reclaim and folio_alloc_swap,
 	 * which can lock swap_slots_cache_mutex.
 	 */
 	slots = kvcalloc(SWAP_SLOTS_CACHE_SIZE, sizeof(swp_entry_t),
@@ -213,7 +213,7 @@ static void __drain_swap_slots_cache(unsigned int type)
 	 * this function can be invoked in the cpu
 	 * hot plug path:
 	 * cpu_up -> lock cpu_hotplug -> cpu hotplug state callback
-	 *   -> memory allocation -> direct reclaim -> get_swap_page
+	 *   -> memory allocation -> direct reclaim -> folio_alloc_swap
 	 *   -> drain_swap_slots_cache
 	 *
 	 * Hence the loop over current online cpu below could miss cpu that
@@ -301,16 +301,16 @@ int free_swap_slot(swp_entry_t entry)
 	return 0;
 }
 
-swp_entry_t get_swap_page(struct page *page)
+swp_entry_t folio_alloc_swap(struct folio *folio)
 {
 	swp_entry_t entry;
 	struct swap_slots_cache *cache;
 
 	entry.val = 0;
 
-	if (PageTransHuge(page)) {
+	if (folio_test_large(folio)) {
 		if (IS_ENABLED(CONFIG_THP_SWAP))
-			get_swap_pages(1, &entry, HPAGE_PMD_NR);
+			get_swap_pages(1, &entry, folio_nr_pages(folio));
 		goto out;
 	}
 
@@ -344,8 +344,8 @@ swp_entry_t get_swap_page(struct page *page)
 
 	get_swap_pages(1, &entry, 1);
 out:
-	if (mem_cgroup_try_charge_swap(page, entry)) {
-		put_swap_page(page, entry);
+	if (mem_cgroup_try_charge_swap(folio, entry)) {
+		put_swap_page(&folio->page, entry);
 		entry.val = 0;
 	}
 	return entry;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 013856004825..989ad18f5468 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -183,13 +183,14 @@ void __delete_from_swap_cache(struct page *page,
  */
 int add_to_swap(struct page *page)
 {
+	struct folio *folio = page_folio(page);
 	swp_entry_t entry;
 	int err;
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	VM_BUG_ON_PAGE(!PageUptodate(page), page);
 
-	entry = get_swap_page(page);
+	entry = folio_alloc_swap(folio);
 	if (!entry.val)
 		return 0;
 
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 63c61f8b2611..c34f41553144 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -76,9 +76,9 @@ static PLIST_HEAD(swap_active_head);
 /*
  * all available (active, not full) swap_info_structs
  * protected with swap_avail_lock, ordered by priority.
- * This is used by get_swap_page() instead of swap_active_head
+ * This is used by folio_alloc_swap() instead of swap_active_head
  * because swap_active_head includes all swap_info_structs,
- * but get_swap_page() doesn't need to look at full ones.
+ * but folio_alloc_swap() doesn't need to look at full ones.
  * This uses its own lock instead of swap_lock because when a
  * swap_info_struct changes between not-full/full, it needs to
  * add/remove itself to/from this list, but the swap_info_struct->lock
@@ -2093,11 +2093,12 @@ static int try_to_unuse(unsigned int type)
 	 * Under global memory pressure, swap entries can be reinserted back
 	 * into process space after the mmlist loop above passes over them.
 	 *
-	 * Limit the number of retries? No: when mmget_not_zero() above fails,
-	 * that mm is likely to be freeing swap from exit_mmap(), which proceeds
-	 * at its own independent pace; and even shmem_writepage() could have
-	 * been preempted after get_swap_page(), temporarily hiding that swap.
-	 * It's easy and robust (though cpu-intensive) just to keep retrying.
+	 * Limit the number of retries? No: when mmget_not_zero()
+	 * above fails, that mm is likely to be freeing swap from
+	 * exit_mmap(), which proceeds at its own independent pace;
+	 * and even shmem_writepage() could have been preempted after
+	 * folio_alloc_swap(), temporarily hiding that swap.  It's easy
+	 * and robust (though cpu-intensive) just to keep retrying.
 	 */
 	if (READ_ONCE(si->inuse_pages)) {
 		if (!signal_pending(current))
@@ -2310,7 +2311,7 @@ static void _enable_swap_info(struct swap_info_struct *p)
 	 * which on removal of any swap_info_struct with an auto-assigned
 	 * (i.e. negative) priority increments the auto-assigned priority
 	 * of any lower-priority swap_info_structs.
-	 * swap_avail_head needs to be priority ordered for get_swap_page(),
+	 * swap_avail_head needs to be priority ordered for folio_alloc_swap(),
 	 * which allocates swap pages from the highest available priority
 	 * swap_info_struct.
 	 */
-- 
2.34.1

[PATCH 07/21] swap: Convert add_to_swap() to take a folio

[Matthew Wilcox (Oracle)]

The only caller already has a folio available, so this saves a conversion.
Also convert the return type to boolean.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/swap.h |  6 +++---
 mm/swap_state.c      | 47 +++++++++++++++++++++++---------------------
 mm/vmscan.c          |  6 +++---
 3 files changed, 31 insertions(+), 28 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 147a9a173508..f87bb495e482 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -449,7 +449,7 @@ static inline unsigned long total_swapcache_pages(void)
 }
 
 extern void show_swap_cache_info(void);
-extern int add_to_swap(struct page *page);
+bool add_to_swap(struct folio *folio);
 extern void *get_shadow_from_swap_cache(swp_entry_t entry);
 extern int add_to_swap_cache(struct page *page, swp_entry_t entry,
 			gfp_t gfp, void **shadowp);
@@ -630,9 +630,9 @@ struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
 	return find_get_page(mapping, index);
 }
 
-static inline int add_to_swap(struct page *page)
+static inline bool add_to_swap(struct folio *folio)
 {
-	return 0;
+	return false;
 }
 
 static inline void *get_shadow_from_swap_cache(swp_entry_t entry)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 989ad18f5468..858d8904b06e 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -175,24 +175,26 @@ void __delete_from_swap_cache(struct page *page,
 }
 
 /**
- * add_to_swap - allocate swap space for a page
- * @page: page we want to move to swap
+ * add_to_swap - allocate swap space for a folio
+ * @folio: folio we want to move to swap
  *
- * Allocate swap space for the page and add the page to the
- * swap cache.  Caller needs to hold the page lock. 
+ * Allocate swap space for the folio and add the folio to the
+ * swap cache.
+ *
+ * Context: Caller needs to hold the folio lock.
+ * Return: Whether the folio was added to the swap cache.
  */
-int add_to_swap(struct page *page)
+bool add_to_swap(struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	swp_entry_t entry;
 	int err;
 
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	VM_BUG_ON_PAGE(!PageUptodate(page), page);
+	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+	VM_BUG_ON_FOLIO(!folio_test_uptodate(folio), folio);
 
 	entry = folio_alloc_swap(folio);
 	if (!entry.val)
-		return 0;
+		return false;
 
 	/*
 	 * XArray node allocations from PF_MEMALLOC contexts could
@@ -205,7 +207,7 @@ int add_to_swap(struct page *page)
 	/*
 	 * Add it to the swap cache.
 	 */
-	err = add_to_swap_cache(page, entry,
+	err = add_to_swap_cache(&folio->page, entry,
 			__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
 	if (err)
 		/*
@@ -214,22 +216,23 @@ int add_to_swap(struct page *page)
 		 */
 		goto fail;
 	/*
-	 * Normally the page will be dirtied in unmap because its pte should be
-	 * dirty. A special case is MADV_FREE page. The page's pte could have
-	 * dirty bit cleared but the page's SwapBacked bit is still set because
-	 * clearing the dirty bit and SwapBacked bit has no lock protected. For
-	 * such page, unmap will not set dirty bit for it, so page reclaim will
-	 * not write the page out. This can cause data corruption when the page
-	 * is swap in later. Always setting the dirty bit for the page solves
-	 * the problem.
+	 * Normally the folio will be dirtied in unmap because its
+	 * pte should be dirty. A special case is MADV_FREE page. The
+	 * page's pte could have dirty bit cleared but the folio's
+	 * SwapBacked flag is still set because clearing the dirty bit
+	 * and SwapBacked flag has no lock protected. For such folio,
+	 * unmap will not set dirty bit for it, so folio reclaim will
+	 * not write the folio out. This can cause data corruption when
+	 * the folio is swapped in later. Always setting the dirty flag
+	 * for the folio solves the problem.
 	 */
-	set_page_dirty(page);
+	folio_mark_dirty(folio);
 
-	return 1;
+	return true;
 
 fail:
-	put_swap_page(page, entry);
-	return 0;
+	put_swap_page(&folio->page, entry);
+	return false;
 }
 
 /*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 19c1bcd886ef..8f7c32b3d65e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1710,8 +1710,8 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 								page_list))
 						goto activate_locked;
 				}
-				if (!add_to_swap(page)) {
-					if (!PageTransHuge(page))
+				if (!add_to_swap(folio)) {
+					if (!folio_test_large(folio))
 						goto activate_locked_split;
 					/* Fallback to swap normal pages */
 					if (split_folio_to_list(folio,
@@ -1720,7 +1720,7 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 					count_vm_event(THP_SWPOUT_FALLBACK);
 #endif
-					if (!add_to_swap(page))
+					if (!add_to_swap(folio))
 						goto activate_locked_split;
 				}
 
-- 
2.34.1

[PATCH 08/21] vmscan: Convert dirty page handling to folios

[Matthew Wilcox (Oracle)]

Mostly this just eliminates calls to compound_head(), but
NR_VMSCAN_IMMEDIATE was being incremented by 1 instead of by nr_pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/vmscan.c | 48 ++++++++++++++++++++++++++----------------------
 1 file changed, 26 insertions(+), 22 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8f7c32b3d65e..950eeb2f759b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1768,28 +1768,31 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			}
 		}
 
-		if (PageDirty(page)) {
+		if (folio_test_dirty(folio)) {
 			/*
-			 * Only kswapd can writeback filesystem pages
+			 * Only kswapd can writeback filesystem folios
 			 * to avoid risk of stack overflow. But avoid
-			 * injecting inefficient single-page IO into
+			 * injecting inefficient single-folio I/O into
 			 * flusher writeback as much as possible: only
-			 * write pages when we've encountered many
-			 * dirty pages, and when we've already scanned
-			 * the rest of the LRU for clean pages and see
-			 * the same dirty pages again (PageReclaim).
+			 * write folios when we've encountered many
+			 * dirty folios, and when we've already scanned
+			 * the rest of the LRU for clean folios and see
+			 * the same dirty folios again (with the reclaim
+			 * flag set).
 			 */
-			if (page_is_file_lru(page) &&
-			    (!current_is_kswapd() || !PageReclaim(page) ||
+			if (folio_is_file_lru(folio) &&
+			    (!current_is_kswapd() ||
+			     !folio_test_reclaim(folio) ||
 			     !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
 				/*
 				 * Immediately reclaim when written back.
-				 * Similar in principal to deactivate_page()
-				 * except we already have the page isolated
+				 * Similar in principle to deactivate_page()
+				 * except we already have the folio isolated
 				 * and know it's dirty
 				 */
-				inc_node_page_state(page, NR_VMSCAN_IMMEDIATE);
-				SetPageReclaim(page);
+				node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE,
+						nr_pages);
+				folio_set_reclaim(folio);
 
 				goto activate_locked;
 			}
@@ -1802,8 +1805,8 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 				goto keep_locked;
 
 			/*
-			 * Page is dirty. Flush the TLB if a writable entry
-			 * potentially exists to avoid CPU writes after IO
+			 * Folio is dirty. Flush the TLB if a writable entry
+			 * potentially exists to avoid CPU writes after I/O
 			 * starts and then write it out here.
 			 */
 			try_to_unmap_flush_dirty();
@@ -1815,23 +1818,24 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			case PAGE_SUCCESS:
 				stat->nr_pageout += nr_pages;
 
-				if (PageWriteback(page))
+				if (folio_test_writeback(folio))
 					goto keep;
-				if (PageDirty(page))
+				if (folio_test_dirty(folio))
 					goto keep;
 
 				/*
 				 * A synchronous write - probably a ramdisk.  Go
-				 * ahead and try to reclaim the page.
+				 * ahead and try to reclaim the folio.
 				 */
-				if (!trylock_page(page))
+				if (!folio_trylock(folio))
 					goto keep;
-				if (PageDirty(page) || PageWriteback(page))
+				if (folio_test_dirty(folio) ||
+				    folio_test_writeback(folio))
 					goto keep_locked;
-				mapping = page_mapping(page);
+				mapping = folio_mapping(folio);
 				fallthrough;
 			case PAGE_CLEAN:
-				; /* try to free the page below */
+				; /* try to free the folio below */
 			}
 		}
 
-- 
2.34.1

[PATCH 09/21] vmscan: Convert page buffer handling to use folios

[Matthew Wilcox (Oracle)]

This mostly just removes calls to compound_head() although nr_reclaimed
should be incremented by the number of pages, not just 1.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/vmscan.c | 50 ++++++++++++++++++++++++++------------------------
 1 file changed, 26 insertions(+), 24 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 950eeb2f759b..cda43f0bb285 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1840,42 +1840,44 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		}
 
 		/*
-		 * If the page has buffers, try to free the buffer mappings
-		 * associated with this page. If we succeed we try to free
-		 * the page as well.
+		 * If the folio has buffers, try to free the buffer
+		 * mappings associated with this folio. If we succeed
+		 * we try to free the folio as well.
 		 *
-		 * We do this even if the page is PageDirty().
-		 * try_to_release_page() does not perform I/O, but it is
-		 * possible for a page to have PageDirty set, but it is actually
-		 * clean (all its buffers are clean).  This happens if the
-		 * buffers were written out directly, with submit_bh(). ext3
-		 * will do this, as well as the blockdev mapping.
-		 * try_to_release_page() will discover that cleanness and will
-		 * drop the buffers and mark the page clean - it can be freed.
+		 * We do this even if the folio is dirty.
+		 * filemap_release_folio() does not perform I/O, but it
+		 * is possible for a folio to have the dirty flag set,
+		 * but it is actually clean (all its buffers are clean).
+		 * This happens if the buffers were written out directly,
+		 * with submit_bh(). ext3 will do this, as well as
+		 * the blockdev mapping.  filemap_release_folio() will
+		 * discover that cleanness and will drop the buffers
+		 * and mark the folio clean - it can be freed.
 		 *
-		 * Rarely, pages can have buffers and no ->mapping.  These are
-		 * the pages which were not successfully invalidated in
-		 * truncate_cleanup_page().  We try to drop those buffers here
-		 * and if that worked, and the page is no longer mapped into
-		 * process address space (page_count == 1) it can be freed.
-		 * Otherwise, leave the page on the LRU so it is swappable.
+		 * Rarely, folios can have buffers and no ->mapping.
+		 * These are the folios which were not successfully
+		 * invalidated in truncate_cleanup_folio().  We try to
+		 * drop those buffers here and if that worked, and the
+		 * folio is no longer mapped into process address space
+		 * (refcount == 1) it can be freed.  Otherwise, leave
+		 * the folio on the LRU so it is swappable.
 		 */
-		if (page_has_private(page)) {
-			if (!try_to_release_page(page, sc->gfp_mask))
+		if (folio_has_private(folio)) {
+			if (!filemap_release_folio(folio, sc->gfp_mask))
 				goto activate_locked;
-			if (!mapping && page_count(page) == 1) {
-				unlock_page(page);
-				if (put_page_testzero(page))
+			if (!mapping && folio_ref_count(folio) == 1) {
+				folio_unlock(folio);
+				if (folio_put_testzero(folio))
 					goto free_it;
 				else {
 					/*
 					 * rare race with speculative reference.
 					 * the speculative reference will free
-					 * this page shortly, so we may
+					 * this folio shortly, so we may
 					 * increment nr_reclaimed here (and
 					 * leave it off the LRU).
 					 */
-					nr_reclaimed++;
+					nr_reclaimed += nr_pages;
 					continue;
 				}
 			}
-- 
2.34.1

Re: [PATCH 09/21] vmscan: Convert page buffer handling to use folios

[Andrew Morton]

On Fri, 29 Apr 2022 20:23:17 +0100 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote:

> This mostly just removes calls to compound_head() although nr_reclaimed
> should be incremented by the number of pages, not just 1.

Yup.  This change

> 
>  					 * leave it off the LRU).
>  					 */
> -					nr_reclaimed++;
> +					nr_reclaimed += nr_pages;
>  					continue;
>  				}
>  			}

Was done independently by
https://lkml.kernel.org/r/20220425111232.23182-5-linmiaohe@huawei.com

[PATCH 10/21] vmscan: Convert lazy freeing to folios

[Matthew Wilcox (Oracle)]

Remove a hidden call to compound_head(), and account nr_pages instead
of a single page.  This matches the code in lru_lazyfree_fn() that
accounts nr_pages to PGLAZYFREE.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/memcontrol.h | 14 ++++++++++++++
 mm/vmscan.c                | 18 +++++++++---------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 89b14729d59f..06a16c82558b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1061,6 +1061,15 @@ static inline void count_memcg_page_event(struct page *page,
 		count_memcg_events(memcg, idx, 1);
 }
 
+static inline void count_memcg_folio_events(struct folio *folio,
+		enum vm_event_item idx, unsigned long nr)
+{
+	struct mem_cgroup *memcg = folio_memcg(folio);
+
+	if (memcg)
+		count_memcg_events(memcg, idx, nr);
+}
+
 static inline void count_memcg_event_mm(struct mm_struct *mm,
 					enum vm_event_item idx)
 {
@@ -1498,6 +1507,11 @@ static inline void count_memcg_page_event(struct page *page,
 {
 }
 
+static inline void count_memcg_folio_events(struct folio *folio,
+		enum vm_event_item idx, unsigned long nr)
+{
+}
+
 static inline
 void count_memcg_event_mm(struct mm_struct *mm, enum vm_event_item idx)
 {
diff --git a/mm/vmscan.c b/mm/vmscan.c
index cda43f0bb285..0368ea3e9880 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1883,20 +1883,20 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			}
 		}
 
-		if (PageAnon(page) && !PageSwapBacked(page)) {
+		if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {
 			/* follow __remove_mapping for reference */
-			if (!page_ref_freeze(page, 1))
+			if (!folio_ref_freeze(folio, 1))
 				goto keep_locked;
 			/*
-			 * The page has only one reference left, which is
+			 * The folio has only one reference left, which is
 			 * from the isolation. After the caller puts the
-			 * page back on lru and drops the reference, the
-			 * page will be freed anyway. It doesn't matter
-			 * which lru it goes. So we don't bother checking
-			 * PageDirty here.
+			 * folio back on the lru and drops the reference, the
+			 * folio will be freed anyway. It doesn't matter
+			 * which lru it goes on. So we don't bother checking
+			 * the dirty flag here.
 			 */
-			count_vm_event(PGLAZYFREED);
-			count_memcg_page_event(page, PGLAZYFREED);
+			count_vm_events(PGLAZYFREED, nr_pages);
+			count_memcg_folio_events(folio, PGLAZYFREED, nr_pages);
 		} else if (!mapping || !__remove_mapping(mapping, folio, true,
 							 sc->target_mem_cgroup))
 			goto keep_locked;
-- 
2.34.1

[PATCH 11/21] vmscan: Move initialisation of mapping down

[Matthew Wilcox (Oracle)]

Now that we don't interrogate the BDI for congestion, we can delay looking
up the folio's mapping until we've got further through the function,
reducing register pressure and saving a call to folio_mapping for folios
we're adding to the swap cache.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/vmscan.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0368ea3e9880..9ac2583ca5e5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1568,12 +1568,11 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			stat->nr_unqueued_dirty += nr_pages;
 
 		/*
-		 * Treat this page as congested if the underlying BDI is or if
+		 * Treat this page as congested if
 		 * pages are cycling through the LRU so quickly that the
 		 * pages marked for immediate reclaim are making it to the
 		 * end of the LRU a second time.
 		 */
-		mapping = page_mapping(page);
 		if (writeback && PageReclaim(page))
 			stat->nr_congested += nr_pages;
 
@@ -1725,9 +1724,6 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 				}
 
 				may_enter_fs = true;
-
-				/* Adding to swap updated mapping */
-				mapping = page_mapping(page);
 			}
 		} else if (PageSwapBacked(page) && PageTransHuge(page)) {
 			/* Split shmem THP */
@@ -1768,6 +1764,7 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			}
 		}
 
+		mapping = folio_mapping(folio);
 		if (folio_test_dirty(folio)) {
 			/*
 			 * Only kswapd can writeback filesystem folios
-- 
2.34.1

[PATCH 12/21] vmscan: Convert the activate_locked portion of shrink_page_list to folios

[Matthew Wilcox (Oracle)]

This accounts the number of pages activated correctly for large folios.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/vmscan.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9ac2583ca5e5..85c9758f6f32 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1927,15 +1927,16 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		}
 activate_locked:
 		/* Not a candidate for swapping, so reclaim swap space. */
-		if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
-						PageMlocked(page)))
-			try_to_free_swap(page);
-		VM_BUG_ON_PAGE(PageActive(page), page);
-		if (!PageMlocked(page)) {
-			int type = page_is_file_lru(page);
-			SetPageActive(page);
+		if (folio_test_swapcache(folio) &&
+		    (mem_cgroup_swap_full(&folio->page) ||
+		     folio_test_mlocked(folio)))
+			try_to_free_swap(&folio->page);
+		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
+		if (!folio_test_mlocked(folio)) {
+			int type = folio_is_file_lru(folio);
+			folio_set_active(folio);
 			stat->nr_activate[type] += nr_pages;
-			count_memcg_page_event(page, PGACTIVATE);
+			count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
 		}
 keep_locked:
 		unlock_page(page);
-- 
2.34.1

[PATCH 13/21] vmscan: Remove remaining uses of page in shrink_page_list

[Matthew Wilcox (Oracle)]

These are all straightforward conversions to the folio API.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/vmscan.c | 115 ++++++++++++++++++++++++++--------------------------
 1 file changed, 57 insertions(+), 58 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 85c9758f6f32..cc9b93c7fa0c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1524,7 +1524,6 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 retry:
 	while (!list_empty(page_list)) {
 		struct address_space *mapping;
-		struct page *page;
 		struct folio *folio;
 		enum page_references references = PAGEREF_RECLAIM;
 		bool dirty, writeback, may_enter_fs;
@@ -1534,31 +1533,31 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 
 		folio = lru_to_folio(page_list);
 		list_del(&folio->lru);
-		page = &folio->page;
 
-		if (!trylock_page(page))
+		if (!folio_trylock(folio))
 			goto keep;
 
-		VM_BUG_ON_PAGE(PageActive(page), page);
+		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
 
-		nr_pages = compound_nr(page);
+		nr_pages = folio_nr_pages(folio);
 
-		/* Account the number of base pages even though THP */
+		/* Account the number of base pages */
 		sc->nr_scanned += nr_pages;
 
-		if (unlikely(!page_evictable(page)))
+		if (unlikely(!folio_evictable(folio)))
 			goto activate_locked;
 
 		if (!sc->may_unmap && folio_mapped(folio))
 			goto keep_locked;
 
 		may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
-			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
+			       (folio_test_swapcache(folio) &&
+				(sc->gfp_mask & __GFP_IO));
 
 		/*
 		 * The number of dirty pages determines if a node is marked
 		 * reclaim_congested. kswapd will stall and start writing
-		 * pages if the tail of the LRU is all dirty unqueued pages.
+		 * folios if the tail of the LRU is all dirty unqueued folios.
 		 */
 		folio_check_dirty_writeback(folio, &dirty, &writeback);
 		if (dirty || writeback)
@@ -1568,21 +1567,21 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			stat->nr_unqueued_dirty += nr_pages;
 
 		/*
-		 * Treat this page as congested if
-		 * pages are cycling through the LRU so quickly that the
-		 * pages marked for immediate reclaim are making it to the
-		 * end of the LRU a second time.
+		 * Treat this folio as congested if folios are cycling
+		 * through the LRU so quickly that the folios marked
+		 * for immediate reclaim are making it to the end of
+		 * the LRU a second time.
 		 */
-		if (writeback && PageReclaim(page))
+		if (writeback && folio_test_reclaim(folio))
 			stat->nr_congested += nr_pages;
 
 		/*
 		 * If a folio at the tail of the LRU is under writeback, there
 		 * are three cases to consider.
 		 *
-		 * 1) If reclaim is encountering an excessive number of folios
-		 *    under writeback and this folio is both under
-		 *    writeback and has the reclaim flag set then it
+		 * 1) If reclaim is encountering an excessive number
+		 *    of folios under writeback and this folio has both
+		 *    the writeback and reclaim flags set, then it
 		 *    indicates that folios are being queued for I/O but
 		 *    are being recycled through the LRU before the I/O
 		 *    can complete. Waiting on the folio itself risks an
@@ -1633,16 +1632,16 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			    !folio_test_reclaim(folio) || !may_enter_fs) {
 				/*
 				 * This is slightly racy -
-				 * folio_end_writeback() might have just
-				 * cleared the reclaim flag, then setting
-				 * reclaim here ends up interpreted as
-				 * the readahead flag - but that does
-				 * not matter enough to care.  What we
-				 * do want is for this folio to have
-				 * the reclaim flag set next time memcg
-				 * reclaim reaches the tests above, so
-				 * it will then folio_wait_writeback()
-				 * to avoid OOM; and it's also appropriate
+				 * folio_end_writeback() might have
+				 * just cleared the reclaim flag, then
+				 * setting the reclaim flag here ends up
+				 * interpreted as the readahead flag - but
+				 * that does not matter enough to care.
+				 * What we do want is for this folio to
+				 * have the reclaim flag set next time
+				 * memcg reclaim reaches the tests above,
+				 * so it will then wait for writeback to
+				 * avoid OOM; and it's also appropriate
 				 * in global reclaim.
 				 */
 				folio_set_reclaim(folio);
@@ -1670,37 +1669,37 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			goto keep_locked;
 		case PAGEREF_RECLAIM:
 		case PAGEREF_RECLAIM_CLEAN:
-			; /* try to reclaim the page below */
+			; /* try to reclaim the folio below */
 		}
 
 		/*
-		 * Before reclaiming the page, try to relocate
+		 * Before reclaiming the folio, try to relocate
 		 * its contents to another node.
 		 */
 		if (do_demote_pass &&
-		    (thp_migration_supported() || !PageTransHuge(page))) {
-			list_add(&page->lru, &demote_pages);
-			unlock_page(page);
+		    (thp_migration_supported() || !folio_test_large(folio))) {
+			list_add(&folio->lru, &demote_pages);
+			folio_unlock(folio);
 			continue;
 		}
 
 		/*
 		 * Anonymous process memory has backing store?
 		 * Try to allocate it some swap space here.
-		 * Lazyfree page could be freed directly
+		 * Lazyfree folio could be freed directly
 		 */
-		if (PageAnon(page) && PageSwapBacked(page)) {
-			if (!PageSwapCache(page)) {
+		if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
+			if (!folio_test_swapcache(folio)) {
 				if (!(sc->gfp_mask & __GFP_IO))
 					goto keep_locked;
 				if (folio_maybe_dma_pinned(folio))
 					goto keep_locked;
-				if (PageTransHuge(page)) {
-					/* cannot split THP, skip it */
+				if (folio_test_large(folio)) {
+					/* cannot split folio, skip it */
 					if (!can_split_folio(folio, NULL))
 						goto activate_locked;
 					/*
-					 * Split pages without a PMD map right
+					 * Split folios without a PMD map right
 					 * away. Chances are some or all of the
 					 * tail pages can be freed without IO.
 					 */
@@ -1725,20 +1724,19 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 
 				may_enter_fs = true;
 			}
-		} else if (PageSwapBacked(page) && PageTransHuge(page)) {
-			/* Split shmem THP */
+		} else if (folio_test_swapbacked(folio) &&
+			   folio_test_large(folio)) {
+			/* Split shmem folio */
 			if (split_folio_to_list(folio, page_list))
 				goto keep_locked;
 		}
 
 		/*
-		 * THP may get split above, need minus tail pages and update
-		 * nr_pages to avoid accounting tail pages twice.
-		 *
-		 * The tail pages that are added into swap cache successfully
-		 * reach here.
+		 * If the folio was split above, the tail pages will make
+		 * their own pass through this function and be accounted
+		 * then.
 		 */
-		if ((nr_pages > 1) && !PageTransHuge(page)) {
+		if ((nr_pages > 1) && !folio_test_large(folio)) {
 			sc->nr_scanned -= (nr_pages - 1);
 			nr_pages = 1;
 		}
@@ -1898,11 +1896,11 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 							 sc->target_mem_cgroup))
 			goto keep_locked;
 
-		unlock_page(page);
+		folio_unlock(folio);
 free_it:
 		/*
-		 * THP may get swapped out in a whole, need account
-		 * all base pages.
+		 * Folio may get swapped out as a whole, need to account
+		 * all pages in it.
 		 */
 		nr_reclaimed += nr_pages;
 
@@ -1910,10 +1908,10 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		 * Is there need to periodically free_page_list? It would
 		 * appear not as the counts should be low
 		 */
-		if (unlikely(PageTransHuge(page)))
-			destroy_compound_page(page);
+		if (unlikely(folio_test_large(folio)))
+			destroy_compound_page(&folio->page);
 		else
-			list_add(&page->lru, &free_pages);
+			list_add(&folio->lru, &free_pages);
 		continue;
 
 activate_locked_split:
@@ -1939,18 +1937,19 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
 		}
 keep_locked:
-		unlock_page(page);
+		folio_unlock(folio);
 keep:
-		list_add(&page->lru, &ret_pages);
-		VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
+		list_add(&folio->lru, &ret_pages);
+		VM_BUG_ON_FOLIO(folio_test_lru(folio) ||
+				folio_test_unevictable(folio), folio);
 	}
 	/* 'page_list' is always empty here */
 
-	/* Migrate pages selected for demotion */
+	/* Migrate folios selected for demotion */
 	nr_reclaimed += demote_page_list(&demote_pages, pgdat);
-	/* Pages that could not be demoted are still in @demote_pages */
+	/* Folios that could not be demoted are still in @demote_pages */
 	if (!list_empty(&demote_pages)) {
-		/* Pages which failed to demoted go back on @page_list for retry: */
+		/* Folios which weren't demoted go back on @page_list for retry: */
 		list_splice_init(&demote_pages, page_list);
 		do_demote_pass = false;
 		goto retry;
-- 
2.34.1

[PATCH 14/21] mm/shmem: Use a folio in shmem_unused_huge_shrink

[Matthew Wilcox (Oracle)]

When calling split_huge_page() we usually have to find the precise page,
but that's not necessary here because we only need to unlock and put
the folio afterwards.  Saves 231 bytes of text (20% of this function).

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/shmem.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 85c23696efc6..3461bdec6b38 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -553,7 +553,7 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 	LIST_HEAD(to_remove);
 	struct inode *inode;
 	struct shmem_inode_info *info;
-	struct page *page;
+	struct folio *folio;
 	unsigned long batch = sc ? sc->nr_to_scan : 128;
 	int split = 0;
 
@@ -597,6 +597,7 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 
 	list_for_each_safe(pos, next, &list) {
 		int ret;
+		pgoff_t index;
 
 		info = list_entry(pos, struct shmem_inode_info, shrinklist);
 		inode = &info->vfs_inode;
@@ -604,14 +605,14 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 		if (nr_to_split && split >= nr_to_split)
 			goto move_back;
 
-		page = find_get_page(inode->i_mapping,
-				(inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
-		if (!page)
+		index = (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT;
+		folio = filemap_get_folio(inode->i_mapping, index);
+		if (!folio)
 			goto drop;
 
 		/* No huge page at the end of the file: nothing to split */
-		if (!PageTransHuge(page)) {
-			put_page(page);
+		if (!folio_test_large(folio)) {
+			folio_put(folio);
 			goto drop;
 		}
 
@@ -622,14 +623,14 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 		 * Waiting for the lock may lead to deadlock in the
 		 * reclaim path.
 		 */
-		if (!trylock_page(page)) {
-			put_page(page);
+		if (!folio_trylock(folio)) {
+			folio_put(folio);
 			goto move_back;
 		}
 
-		ret = split_huge_page(page);
-		unlock_page(page);
-		put_page(page);
+		ret = split_huge_page(&folio->page);
+		folio_unlock(folio);
+		folio_put(folio);
 
 		/* If split failed move the inode on the list back to shrinklist */
 		if (ret)
-- 
2.34.1

[PATCH 15/21] mm/swap: Add folio_throttle_swaprate

[Matthew Wilcox (Oracle)]

The only use of the page argument to cgroup_throttle_swaprate() is to
get the node ID, and this will be the same for all pages in the folio,
so just pass in the first page of the folio.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/swap.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index f87bb495e482..96f7129f6ee2 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -736,6 +736,10 @@ static inline void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
 {
 }
 #endif
+static inline void folio_throttle_swaprate(struct folio *folio, gfp_t gfp)
+{
+	cgroup_throttle_swaprate(&folio->page, gfp);
+}
 
 #ifdef CONFIG_MEMCG_SWAP
 void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry);
-- 
2.34.1

[PATCH 16/21] mm/shmem: Convert shmem_add_to_page_cache to take a folio

[Matthew Wilcox (Oracle)]

Shrinks shmem_add_to_page_cache() by 16 bytes.  All the callers grow,
but this is temporary as they will all be converted to folios soon.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/shmem.c | 57 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 31 insertions(+), 26 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 3461bdec6b38..4331a4daac01 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -695,36 +695,35 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 /*
  * Like add_to_page_cache_locked, but error if expected item has gone.
  */
-static int shmem_add_to_page_cache(struct page *page,
+static int shmem_add_to_page_cache(struct folio *folio,
 				   struct address_space *mapping,
 				   pgoff_t index, void *expected, gfp_t gfp,
 				   struct mm_struct *charge_mm)
 {
-	XA_STATE_ORDER(xas, &mapping->i_pages, index, compound_order(page));
-	unsigned long nr = compound_nr(page);
+	XA_STATE_ORDER(xas, &mapping->i_pages, index, folio_order(folio));
+	long nr = folio_nr_pages(folio);
 	int error;
 
-	VM_BUG_ON_PAGE(PageTail(page), page);
-	VM_BUG_ON_PAGE(index != round_down(index, nr), page);
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
-	VM_BUG_ON(expected && PageTransHuge(page));
+	VM_BUG_ON_FOLIO(index != round_down(index, nr), folio);
+	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+	VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
+	VM_BUG_ON(expected && folio_test_large(folio));
 
-	page_ref_add(page, nr);
-	page->mapping = mapping;
-	page->index = index;
+	folio_ref_add(folio, nr);
+	folio->mapping = mapping;
+	folio->index = index;
 
-	if (!PageSwapCache(page)) {
-		error = mem_cgroup_charge(page_folio(page), charge_mm, gfp);
+	if (!folio_test_swapcache(folio)) {
+		error = mem_cgroup_charge(folio, charge_mm, gfp);
 		if (error) {
-			if (PageTransHuge(page)) {
+			if (folio_test_large(folio)) {
 				count_vm_event(THP_FILE_FALLBACK);
 				count_vm_event(THP_FILE_FALLBACK_CHARGE);
 			}
 			goto error;
 		}
 	}
-	cgroup_throttle_swaprate(page, gfp);
+	folio_throttle_swaprate(folio, gfp);
 
 	do {
 		xas_lock_irq(&xas);
@@ -736,16 +735,16 @@ static int shmem_add_to_page_cache(struct page *page,
 			xas_set_err(&xas, -EEXIST);
 			goto unlock;
 		}
-		xas_store(&xas, page);
+		xas_store(&xas, folio);
 		if (xas_error(&xas))
 			goto unlock;
-		if (PageTransHuge(page)) {
+		if (folio_test_large(folio)) {
 			count_vm_event(THP_FILE_ALLOC);
-			__mod_lruvec_page_state(page, NR_SHMEM_THPS, nr);
+			__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
 		}
 		mapping->nrpages += nr;
-		__mod_lruvec_page_state(page, NR_FILE_PAGES, nr);
-		__mod_lruvec_page_state(page, NR_SHMEM, nr);
+		__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
+		__lruvec_stat_mod_folio(folio, NR_SHMEM, nr);
 unlock:
 		xas_unlock_irq(&xas);
 	} while (xas_nomem(&xas, gfp));
@@ -757,8 +756,8 @@ static int shmem_add_to_page_cache(struct page *page,
 
 	return 0;
 error:
-	page->mapping = NULL;
-	page_ref_sub(page, nr);
+	folio->mapping = NULL;
+	folio_ref_sub(folio, nr);
 	return error;
 }
 
@@ -1690,7 +1689,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	struct address_space *mapping = inode->i_mapping;
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
-	struct page *page;
+	struct page *page = NULL;
+	struct folio *folio;
 	swp_entry_t swap;
 	int error;
 
@@ -1740,7 +1740,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 			goto failed;
 	}
 
-	error = shmem_add_to_page_cache(page, mapping, index,
+	folio = page_folio(page);
+	error = shmem_add_to_page_cache(folio, mapping, index,
 					swp_to_radix_entry(swap), gfp,
 					charge_mm);
 	if (error)
@@ -1791,6 +1792,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct shmem_sb_info *sbinfo;
 	struct mm_struct *charge_mm;
+	struct folio *folio;
 	struct page *page;
 	pgoff_t hindex = index;
 	gfp_t huge_gfp;
@@ -1905,7 +1907,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	if (sgp == SGP_WRITE)
 		__SetPageReferenced(page);
 
-	error = shmem_add_to_page_cache(page, mapping, hindex,
+	folio = page_folio(page);
+	error = shmem_add_to_page_cache(folio, mapping, hindex,
 					NULL, gfp & GFP_RECLAIM_MASK,
 					charge_mm);
 	if (error)
@@ -2327,6 +2330,7 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 	gfp_t gfp = mapping_gfp_mask(mapping);
 	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
 	void *page_kaddr;
+	struct folio *folio;
 	struct page *page;
 	int ret;
 	pgoff_t max_off;
@@ -2385,7 +2389,8 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 	if (unlikely(pgoff >= max_off))
 		goto out_release;
 
-	ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL,
+	folio = page_folio(page);
+	ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL,
 				      gfp & GFP_RECLAIM_MASK, dst_mm);
 	if (ret)
 		goto out_release;
-- 
2.34.1

Re: [PATCH 16/21] mm/shmem: Convert shmem_add_to_page_cache to take a folio

[Sebastian Andrzej Siewior]

On 2022-04-29 20:23:24 [+0100], Matthew Wilcox (Oracle) wrote:
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 3461bdec6b38..4331a4daac01 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -736,16 +735,16 @@ static int shmem_add_to_page_cache(struct page *page,
>  			xas_set_err(&xas, -EEXIST);
>  			goto unlock;
>  		}
> -		xas_store(&xas, page);
> +		xas_store(&xas, folio);
>  		if (xas_error(&xas))
>  			goto unlock;
> -		if (PageTransHuge(page)) {
> +		if (folio_test_large(folio)) {
>  			count_vm_event(THP_FILE_ALLOC);
> -			__mod_lruvec_page_state(page, NR_SHMEM_THPS, nr);
> +			__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
>  		}

|  CC      mm/shmem.o
|In file included from <command-line>:
|mm/shmem.c: In function ‘shmem_add_to_page_cache’:
|include/linux/compiler_types.h:352:45: error: call to ‘__compiletime_assert_262’ declared with attribute error: BUILD_BUG failed
|  352 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
|      |                                             ^
…
|mm/shmem.c:743:40: note: in expansion of macro ‘THP_FILE_ALLOC’
|  743 |                         count_vm_event(THP_FILE_ALLOC);
|      |                                        ^~~~~~~~~~~~~~
|

and 

| $ git grep THP_FILE_ALLOC
| include/linux/vm_event_item.h:          THP_FILE_ALLOC,
| include/linux/vm_event_item.h:#define THP_FILE_ALLOC ({ BUILD_BUG(); 0; })
| mm/shmem.c:                     count_vm_event(THP_FILE_ALLOC);
| $ grep CONFIG_TRANSPARENT_HUGEPAGE .config
| # CONFIG_TRANSPARENT_HUGEPAGE is not set

Sebastian

Re: [PATCH 16/21] mm/shmem: Convert shmem_add_to_page_cache to take a folio

[Matthew Wilcox]

On Tue, May 03, 2022 at 01:10:09PM +0200, Sebastian Andrzej Siewior wrote:
> On 2022-04-29 20:23:24 [+0100], Matthew Wilcox (Oracle) wrote:
> > diff --git a/mm/shmem.c b/mm/shmem.c
> > index 3461bdec6b38..4331a4daac01 100644
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -736,16 +735,16 @@ static int shmem_add_to_page_cache(struct page *page,
> >  			xas_set_err(&xas, -EEXIST);
> >  			goto unlock;
> >  		}
> > -		xas_store(&xas, page);
> > +		xas_store(&xas, folio);
> >  		if (xas_error(&xas))
> >  			goto unlock;
> > -		if (PageTransHuge(page)) {
> > +		if (folio_test_large(folio)) {
> >  			count_vm_event(THP_FILE_ALLOC);
> > -			__mod_lruvec_page_state(page, NR_SHMEM_THPS, nr);
> > +			__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
> >  		}
> 
> |  CC      mm/shmem.o
> |In file included from <command-line>:
> |mm/shmem.c: In function ‘shmem_add_to_page_cache’:
> |include/linux/compiler_types.h:352:45: error: call to ‘__compiletime_assert_262’ declared with attribute error: BUILD_BUG failed
> |  352 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> |      |                                             ^
> …
> |mm/shmem.c:743:40: note: in expansion of macro ‘THP_FILE_ALLOC’
> |  743 |                         count_vm_event(THP_FILE_ALLOC);

Thanks.  Stephen already reported that; fix here:

https://lore.kernel.org/all/Ym++SI1ftbRg+9zK@casper.infradead.org/

Re: [PATCH 16/21] mm/shmem: Convert shmem_add_to_page_cache to take a folio

[Sebastian Andrzej Siewior]

On 2022-05-03 13:48:50 [+0100], Matthew Wilcox wrote:
> Thanks.  Stephen already reported that; fix here:
> 
> https://lore.kernel.org/all/Ym++SI1ftbRg+9zK@casper.infradead.org/

Stephen says "I applied the above patch to the mm tree merge today" and
I have here next-20220503. I don't have the BUILD_BUG() in
can_split_folio() anymore so I have this change.

My guess is that since THP_FILE_ALLOC is defined as BUILD_BUG() for
!CONFIG_TRANSPARENT_HUGEPAGE and there is nothing that removes that part
of the code, I end up in BUILD_BUG with CGROUP and no THP.

PageTransHuge() used to "return false" for !CONFIG_TRANSPARENT_HUGEPAGE
which isn't the case for folio_test_large().

Sebastian

Re: [PATCH 16/21] mm/shmem: Convert shmem_add_to_page_cache to take a folio

[Matthew Wilcox]

On Tue, May 03, 2022 at 03:00:05PM +0200, Sebastian Andrzej Siewior wrote:
> On 2022-05-03 13:48:50 [+0100], Matthew Wilcox wrote:
> > Thanks.  Stephen already reported that; fix here:
> > 
> > https://lore.kernel.org/all/Ym++SI1ftbRg+9zK@casper.infradead.org/
> 
> Stephen says "I applied the above patch to the mm tree merge today" and
> I have here next-20220503. I don't have the BUILD_BUG() in
> can_split_folio() anymore so I have this change.

Ah!  I didn't realise you were testing next; I thought you'd picked up
these patches some other way.

> My guess is that since THP_FILE_ALLOC is defined as BUILD_BUG() for
> !CONFIG_TRANSPARENT_HUGEPAGE and there is nothing that removes that part
> of the code, I end up in BUILD_BUG with CGROUP and no THP.
> 
> PageTransHuge() used to "return false" for !CONFIG_TRANSPARENT_HUGEPAGE
> which isn't the case for folio_test_large().

Indeed, indeed.  I missed another case.  This fixes it:

diff --git a/mm/shmem.c b/mm/shmem.c
index 5b161a92e6f1..019ad8bf0d21 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -716,7 +716,7 @@ static int shmem_add_to_page_cache(struct folio *folio,
 	if (!folio_test_swapcache(folio)) {
 		error = mem_cgroup_charge(folio, charge_mm, gfp);
 		if (error) {
-			if (folio_test_large(folio)) {
+			if (folio_test_pmd_mappable(folio)) {
 				count_vm_event(THP_FILE_FALLBACK);
 				count_vm_event(THP_FILE_FALLBACK_CHARGE);
 			}

Re: [PATCH 16/21] mm/shmem: Convert shmem_add_to_page_cache to take a folio

[Sebastian Andrzej Siewior]

On 2022-05-03 14:05:25 [+0100], Matthew Wilcox wrote:
> Indeed, indeed.  I missed another case.  This fixes it:

Yup, thank you. This works.

Sebastian

[PATCH 17/21] mm/shmem: Turn shmem_should_replace_page into shmem_should_replace_folio

[Matthew Wilcox (Oracle)]

This is a straightforward conversion.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/shmem.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 4331a4daac01..4b8d0972bf72 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1600,9 +1600,9 @@ static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
  * but for now it is a simple matter of zone.
  */
-static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
+static bool shmem_should_replace_folio(struct folio *folio, gfp_t gfp)
 {
-	return page_zonenum(page) > gfp_zone(gfp);
+	return folio_zonenum(folio) > gfp_zone(gfp);
 }
 
 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
@@ -1734,13 +1734,13 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	 */
 	arch_swap_restore(swap, page);
 
-	if (shmem_should_replace_page(page, gfp)) {
+	folio = page_folio(page);
+	if (shmem_should_replace_folio(folio, gfp)) {
 		error = shmem_replace_page(&page, gfp, info, index);
 		if (error)
 			goto failed;
 	}
 
-	folio = page_folio(page);
 	error = shmem_add_to_page_cache(folio, mapping, index,
 					swp_to_radix_entry(swap), gfp,
 					charge_mm);
-- 
2.34.1

[PATCH 18/21] mm/shmem: Turn shmem_alloc_page() into shmem_alloc_folio()

[Matthew Wilcox (Oracle)]

Call vma_alloc_folio() directly instead of alloc_page_vma().
It's a bit messy in the callers, but they're about to be
cleaned up when they get converted to folios.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/shmem.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 4b8d0972bf72..afee80747647 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1543,17 +1543,17 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 	return &folio->page;
 }
 
-static struct page *shmem_alloc_page(gfp_t gfp,
+static struct folio *shmem_alloc_folio(gfp_t gfp,
 			struct shmem_inode_info *info, pgoff_t index)
 {
 	struct vm_area_struct pvma;
-	struct page *page;
+	struct folio *folio;
 
 	shmem_pseudo_vma_init(&pvma, info, index);
-	page = alloc_page_vma(gfp, &pvma, 0);
+	folio = vma_alloc_folio(gfp, 0, &pvma, 0, false);
 	shmem_pseudo_vma_destroy(&pvma);
 
-	return page;
+	return folio;
 }
 
 static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
@@ -1575,7 +1575,7 @@ static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
 	if (huge)
 		page = shmem_alloc_hugepage(gfp, info, index);
 	else
-		page = shmem_alloc_page(gfp, info, index);
+		page = &shmem_alloc_folio(gfp, info, index)->page;
 	if (page) {
 		__SetPageLocked(page);
 		__SetPageSwapBacked(page);
@@ -1625,7 +1625,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 	 * limit chance of success by further cpuset and node constraints.
 	 */
 	gfp &= ~GFP_CONSTRAINT_MASK;
-	newpage = shmem_alloc_page(gfp, info, index);
+	newpage = &shmem_alloc_folio(gfp, info, index)->page;
 	if (!newpage)
 		return -ENOMEM;
 
@@ -2350,7 +2350,6 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 
 	if (!*pagep) {
 		ret = -ENOMEM;
-		page = shmem_alloc_page(gfp, info, pgoff);
 		if (!page)
 			goto out_unacct_blocks;
 
-- 
2.34.1

[PATCH 19/21] mm/shmem: Convert shmem_alloc_and_acct_page to use a folio

[Matthew Wilcox (Oracle)]

Convert shmem_alloc_hugepage() to return the folio that it uses
and use a folio throughout shmem_alloc_and_acct_page().  Continue
to return a page from shmem_alloc_and_acct_page() for now.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/shmem.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index afee80747647..e65daf511a9b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1522,7 +1522,7 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
 	return result;
 }
 
-static struct page *shmem_alloc_hugepage(gfp_t gfp,
+static struct folio *shmem_alloc_hugefolio(gfp_t gfp,
 		struct shmem_inode_info *info, pgoff_t index)
 {
 	struct vm_area_struct pvma;
@@ -1540,7 +1540,7 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 	shmem_pseudo_vma_destroy(&pvma);
 	if (!folio)
 		count_vm_event(THP_FILE_FALLBACK);
-	return &folio->page;
+	return folio;
 }
 
 static struct folio *shmem_alloc_folio(gfp_t gfp,
@@ -1561,7 +1561,7 @@ static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
 		pgoff_t index, bool huge)
 {
 	struct shmem_inode_info *info = SHMEM_I(inode);
-	struct page *page;
+	struct folio *folio;
 	int nr;
 	int err = -ENOSPC;
 
@@ -1573,13 +1573,13 @@ static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
 		goto failed;
 
 	if (huge)
-		page = shmem_alloc_hugepage(gfp, info, index);
+		folio = shmem_alloc_hugefolio(gfp, info, index);
 	else
-		page = &shmem_alloc_folio(gfp, info, index)->page;
-	if (page) {
-		__SetPageLocked(page);
-		__SetPageSwapBacked(page);
-		return page;
+		folio = shmem_alloc_folio(gfp, info, index);
+	if (folio) {
+		__folio_set_locked(folio);
+		__folio_set_swapbacked(folio);
+		return &folio->page;
 	}
 
 	err = -ENOMEM;
-- 
2.34.1

[PATCH 20/21] mm/shmem: Convert shmem_getpage_gfp to use a folio

[Matthew Wilcox (Oracle)]

Rename shmem_alloc_and_acct_page() to shmem_alloc_and_acct_folio() and
have it return a folio, then use a folio throuughout shmem_getpage_gfp().
It continues to return a struct page.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/shmem.c | 92 +++++++++++++++++++++++++-----------------------------
 1 file changed, 43 insertions(+), 49 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e65daf511a9b..7457f352cf9f 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1556,8 +1556,7 @@ static struct folio *shmem_alloc_folio(gfp_t gfp,
 	return folio;
 }
 
-static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
-		struct inode *inode,
+static struct folio *shmem_alloc_and_acct_folio(gfp_t gfp, struct inode *inode,
 		pgoff_t index, bool huge)
 {
 	struct shmem_inode_info *info = SHMEM_I(inode);
@@ -1579,7 +1578,7 @@ static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
 	if (folio) {
 		__folio_set_locked(folio);
 		__folio_set_swapbacked(folio);
-		return &folio->page;
+		return folio;
 	}
 
 	err = -ENOMEM;
@@ -1793,7 +1792,6 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	struct shmem_sb_info *sbinfo;
 	struct mm_struct *charge_mm;
 	struct folio *folio;
-	struct page *page;
 	pgoff_t hindex = index;
 	gfp_t huge_gfp;
 	int error;
@@ -1811,19 +1809,18 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	sbinfo = SHMEM_SB(inode->i_sb);
 	charge_mm = vma ? vma->vm_mm : NULL;
 
-	page = pagecache_get_page(mapping, index,
-					FGP_ENTRY | FGP_HEAD | FGP_LOCK, 0);
-
-	if (page && vma && userfaultfd_minor(vma)) {
-		if (!xa_is_value(page)) {
-			unlock_page(page);
-			put_page(page);
+	folio = __filemap_get_folio(mapping, index, FGP_ENTRY | FGP_LOCK, 0);
+	if (folio && vma && userfaultfd_minor(vma)) {
+		if (!xa_is_value(folio)) {
+			folio_unlock(folio);
+			folio_put(folio);
 		}
 		*fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
 		return 0;
 	}
 
-	if (xa_is_value(page)) {
+	if (xa_is_value(folio)) {
+		struct page *page = &folio->page;
 		error = shmem_swapin_page(inode, index, &page,
 					  sgp, gfp, vma, fault_type);
 		if (error == -EEXIST)
@@ -1833,17 +1830,17 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 		return error;
 	}
 
-	if (page) {
-		hindex = page->index;
+	if (folio) {
+		hindex = folio->index;
 		if (sgp == SGP_WRITE)
-			mark_page_accessed(page);
-		if (PageUptodate(page))
+			folio_mark_accessed(folio);
+		if (folio_test_uptodate(folio))
 			goto out;
 		/* fallocated page */
 		if (sgp != SGP_READ)
 			goto clear;
-		unlock_page(page);
-		put_page(page);
+		folio_unlock(folio);
+		folio_put(folio);
 	}
 
 	/*
@@ -1870,17 +1867,16 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 
 	huge_gfp = vma_thp_gfp_mask(vma);
 	huge_gfp = limit_gfp_mask(huge_gfp, gfp);
-	page = shmem_alloc_and_acct_page(huge_gfp, inode, index, true);
-	if (IS_ERR(page)) {
+	folio = shmem_alloc_and_acct_folio(huge_gfp, inode, index, true);
+	if (IS_ERR(folio)) {
 alloc_nohuge:
-		page = shmem_alloc_and_acct_page(gfp, inode,
-						 index, false);
+		folio = shmem_alloc_and_acct_folio(gfp, inode, index, false);
 	}
-	if (IS_ERR(page)) {
+	if (IS_ERR(folio)) {
 		int retry = 5;
 
-		error = PTR_ERR(page);
-		page = NULL;
+		error = PTR_ERR(folio);
+		folio = NULL;
 		if (error != -ENOSPC)
 			goto unlock;
 		/*
@@ -1899,30 +1895,29 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 		goto unlock;
 	}
 
-	if (PageTransHuge(page))
+	if (folio_test_large(folio))
 		hindex = round_down(index, HPAGE_PMD_NR);
 	else
 		hindex = index;
 
 	if (sgp == SGP_WRITE)
-		__SetPageReferenced(page);
+		__folio_set_referenced(folio);
 
-	folio = page_folio(page);
 	error = shmem_add_to_page_cache(folio, mapping, hindex,
 					NULL, gfp & GFP_RECLAIM_MASK,
 					charge_mm);
 	if (error)
 		goto unacct;
-	lru_cache_add(page);
+	folio_add_lru(folio);
 
 	spin_lock_irq(&info->lock);
-	info->alloced += compound_nr(page);
-	inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
+	info->alloced += folio_nr_pages(folio);
+	inode->i_blocks += BLOCKS_PER_PAGE << folio_order(folio);
 	shmem_recalc_inode(inode);
 	spin_unlock_irq(&info->lock);
 	alloced = true;
 
-	if (PageTransHuge(page) &&
+	if (folio_test_large(folio) &&
 	    DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
 			hindex + HPAGE_PMD_NR - 1) {
 		/*
@@ -1953,22 +1948,21 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	 * but SGP_FALLOC on a page fallocated earlier must initialize
 	 * it now, lest undo on failure cancel our earlier guarantee.
 	 */
-	if (sgp != SGP_WRITE && !PageUptodate(page)) {
-		int i;
+	if (sgp != SGP_WRITE && !folio_test_uptodate(folio)) {
+		long i, n = folio_nr_pages(folio);
 
-		for (i = 0; i < compound_nr(page); i++) {
-			clear_highpage(page + i);
-			flush_dcache_page(page + i);
-		}
-		SetPageUptodate(page);
+		for (i = 0; i < n; i++)
+			clear_highpage(folio_page(folio, i));
+		flush_dcache_folio(folio);
+		folio_mark_uptodate(folio);
 	}
 
 	/* Perhaps the file has been truncated since we checked */
 	if (sgp <= SGP_CACHE &&
 	    ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
 		if (alloced) {
-			ClearPageDirty(page);
-			delete_from_page_cache(page);
+			folio_clear_dirty(folio);
+			filemap_remove_folio(folio);
 			spin_lock_irq(&info->lock);
 			shmem_recalc_inode(inode);
 			spin_unlock_irq(&info->lock);
@@ -1977,24 +1971,24 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 		goto unlock;
 	}
 out:
-	*pagep = page + index - hindex;
+	*pagep = folio_page(folio, index - hindex);
 	return 0;
 
 	/*
 	 * Error recovery.
 	 */
 unacct:
-	shmem_inode_unacct_blocks(inode, compound_nr(page));
+	shmem_inode_unacct_blocks(inode, folio_nr_pages(folio));
 
-	if (PageTransHuge(page)) {
-		unlock_page(page);
-		put_page(page);
+	if (folio_test_large(folio)) {
+		folio_unlock(folio);
+		folio_put(folio);
 		goto alloc_nohuge;
 	}
 unlock:
-	if (page) {
-		unlock_page(page);
-		put_page(page);
+	if (folio) {
+		folio_unlock(folio);
+		folio_put(folio);
 	}
 	if (error == -ENOSPC && !once++) {
 		spin_lock_irq(&info->lock);
-- 
2.34.1

[PATCH 21/21] mm/shmem: Convert shmem_swapin_page() to shmem_swapin_folio()

[Matthew Wilcox (Oracle)]

shmem_swapin_page() only brings in order-0 pages, which are folios
by definition.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 arch/arm64/include/asm/pgtable.h |   6 +-
 include/linux/pgtable.h          |   2 +-
 mm/shmem.c                       | 108 ++++++++++++++-----------------
 3 files changed, 54 insertions(+), 62 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index dff2b483ea50..27cb6a355fb0 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -964,10 +964,10 @@ static inline void arch_swap_invalidate_area(int type)
 }
 
 #define __HAVE_ARCH_SWAP_RESTORE
-static inline void arch_swap_restore(swp_entry_t entry, struct page *page)
+static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
 {
-	if (system_supports_mte() && mte_restore_tags(entry, page))
-		set_bit(PG_mte_tagged, &page->flags);
+	if (system_supports_mte() && mte_restore_tags(entry, &folio->page))
+		set_bit(PG_mte_tagged, &folio->flags);
 }
 
 #endif /* CONFIG_ARM64_MTE */
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index f4f4077b97aa..a1c44b015463 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -738,7 +738,7 @@ static inline void arch_swap_invalidate_area(int type)
 #endif
 
 #ifndef __HAVE_ARCH_SWAP_RESTORE
-static inline void arch_swap_restore(swp_entry_t entry, struct page *page)
+static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
 {
 }
 #endif
diff --git a/mm/shmem.c b/mm/shmem.c
index 7457f352cf9f..673a0e783496 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -134,8 +134,8 @@ static unsigned long shmem_default_max_inodes(void)
 }
 #endif
 
-static int shmem_swapin_page(struct inode *inode, pgoff_t index,
-			     struct page **pagep, enum sgp_type sgp,
+static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
+			     struct folio **foliop, enum sgp_type sgp,
 			     gfp_t gfp, struct vm_area_struct *vma,
 			     vm_fault_t *fault_type);
 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
@@ -1158,69 +1158,64 @@ static void shmem_evict_inode(struct inode *inode)
 }
 
 static int shmem_find_swap_entries(struct address_space *mapping,
-				   pgoff_t start, unsigned int nr_entries,
-				   struct page **entries, pgoff_t *indices,
-				   unsigned int type)
+				   pgoff_t start, struct folio_batch *fbatch,
+				   pgoff_t *indices, unsigned int type)
 {
 	XA_STATE(xas, &mapping->i_pages, start);
-	struct page *page;
+	struct folio *folio;
 	swp_entry_t entry;
 	unsigned int ret = 0;
 
-	if (!nr_entries)
-		return 0;
-
 	rcu_read_lock();
-	xas_for_each(&xas, page, ULONG_MAX) {
-		if (xas_retry(&xas, page))
+	xas_for_each(&xas, folio, ULONG_MAX) {
+		if (xas_retry(&xas, folio))
 			continue;
 
-		if (!xa_is_value(page))
+		if (!xa_is_value(folio))
 			continue;
 
-		entry = radix_to_swp_entry(page);
+		entry = radix_to_swp_entry(folio);
 		if (swp_type(entry) != type)
 			continue;
 
 		indices[ret] = xas.xa_index;
-		entries[ret] = page;
+		if (!folio_batch_add(fbatch, folio))
+			break;
 
 		if (need_resched()) {
 			xas_pause(&xas);
 			cond_resched_rcu();
 		}
-		if (++ret == nr_entries)
-			break;
 	}
 	rcu_read_unlock();
 
-	return ret;
+	return xas.xa_index;
 }
 
 /*
  * Move the swapped pages for an inode to page cache. Returns the count
  * of pages swapped in, or the error in case of failure.
  */
-static int shmem_unuse_swap_entries(struct inode *inode, struct pagevec pvec,
-				    pgoff_t *indices)
+static int shmem_unuse_swap_entries(struct inode *inode,
+		struct folio_batch *fbatch, pgoff_t *indices)
 {
 	int i = 0;
 	int ret = 0;
 	int error = 0;
 	struct address_space *mapping = inode->i_mapping;
 
-	for (i = 0; i < pvec.nr; i++) {
-		struct page *page = pvec.pages[i];
+	for (i = 0; i < folio_batch_count(fbatch); i++) {
+		struct folio *folio = fbatch->folios[i];
 
-		if (!xa_is_value(page))
+		if (!xa_is_value(folio))
 			continue;
-		error = shmem_swapin_page(inode, indices[i],
-					  &page, SGP_CACHE,
+		error = shmem_swapin_folio(inode, indices[i],
+					  &folio, SGP_CACHE,
 					  mapping_gfp_mask(mapping),
 					  NULL, NULL);
 		if (error == 0) {
-			unlock_page(page);
-			put_page(page);
+			folio_unlock(folio);
+			folio_put(folio);
 			ret++;
 		}
 		if (error == -ENOMEM)
@@ -1237,26 +1232,23 @@ static int shmem_unuse_inode(struct inode *inode, unsigned int type)
 {
 	struct address_space *mapping = inode->i_mapping;
 	pgoff_t start = 0;
-	struct pagevec pvec;
+	struct folio_batch fbatch;
 	pgoff_t indices[PAGEVEC_SIZE];
 	int ret = 0;
 
-	pagevec_init(&pvec);
 	do {
-		unsigned int nr_entries = PAGEVEC_SIZE;
-
-		pvec.nr = shmem_find_swap_entries(mapping, start, nr_entries,
-						  pvec.pages, indices, type);
-		if (pvec.nr == 0) {
+		folio_batch_init(&fbatch);
+		shmem_find_swap_entries(mapping, start, &fbatch, indices, type);
+		if (folio_batch_count(&fbatch) == 0) {
 			ret = 0;
 			break;
 		}
 
-		ret = shmem_unuse_swap_entries(inode, pvec, indices);
+		ret = shmem_unuse_swap_entries(inode, &fbatch, indices);
 		if (ret < 0)
 			break;
 
-		start = indices[pvec.nr - 1];
+		start = indices[folio_batch_count(&fbatch) - 1];
 	} while (true);
 
 	return ret;
@@ -1680,22 +1672,22 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
  * Returns 0 and the page in pagep if success. On failure, returns the
  * error code and NULL in *pagep.
  */
-static int shmem_swapin_page(struct inode *inode, pgoff_t index,
-			     struct page **pagep, enum sgp_type sgp,
+static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
+			     struct folio **foliop, enum sgp_type sgp,
 			     gfp_t gfp, struct vm_area_struct *vma,
 			     vm_fault_t *fault_type)
 {
 	struct address_space *mapping = inode->i_mapping;
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
-	struct page *page = NULL;
+	struct page *page;
 	struct folio *folio;
 	swp_entry_t swap;
 	int error;
 
-	VM_BUG_ON(!*pagep || !xa_is_value(*pagep));
-	swap = radix_to_swp_entry(*pagep);
-	*pagep = NULL;
+	VM_BUG_ON(!*foliop || !xa_is_value(*foliop));
+	swap = radix_to_swp_entry(*foliop);
+	*foliop = NULL;
 
 	/* Look it up and read it in.. */
 	page = lookup_swap_cache(swap, NULL, 0);
@@ -1713,27 +1705,28 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 			goto failed;
 		}
 	}
+	folio = page_folio(page);
 
 	/* We have to do this with page locked to prevent races */
-	lock_page(page);
-	if (!PageSwapCache(page) || page_private(page) != swap.val ||
+	folio_lock(folio);
+	if (!folio_test_swapcache(folio) ||
+	    folio_swap_entry(folio).val != swap.val ||
 	    !shmem_confirm_swap(mapping, index, swap)) {
 		error = -EEXIST;
 		goto unlock;
 	}
-	if (!PageUptodate(page)) {
+	if (!folio_test_uptodate(folio)) {
 		error = -EIO;
 		goto failed;
 	}
-	wait_on_page_writeback(page);
+	folio_wait_writeback(folio);
 
 	/*
 	 * Some architectures may have to restore extra metadata to the
-	 * physical page after reading from swap.
+	 * folio after reading from swap.
 	 */
-	arch_swap_restore(swap, page);
+	arch_swap_restore(swap, folio);
 
-	folio = page_folio(page);
 	if (shmem_should_replace_folio(folio, gfp)) {
 		error = shmem_replace_page(&page, gfp, info, index);
 		if (error)
@@ -1752,21 +1745,21 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	spin_unlock_irq(&info->lock);
 
 	if (sgp == SGP_WRITE)
-		mark_page_accessed(page);
+		folio_mark_accessed(folio);
 
-	delete_from_swap_cache(page);
-	set_page_dirty(page);
+	delete_from_swap_cache(&folio->page);
+	folio_mark_dirty(folio);
 	swap_free(swap);
 
-	*pagep = page;
+	*foliop = folio;
 	return 0;
 failed:
 	if (!shmem_confirm_swap(mapping, index, swap))
 		error = -EEXIST;
 unlock:
-	if (page) {
-		unlock_page(page);
-		put_page(page);
+	if (folio) {
+		folio_unlock(folio);
+		folio_put(folio);
 	}
 
 	return error;
@@ -1820,13 +1813,12 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	}
 
 	if (xa_is_value(folio)) {
-		struct page *page = &folio->page;
-		error = shmem_swapin_page(inode, index, &page,
+		error = shmem_swapin_folio(inode, index, &folio,
 					  sgp, gfp, vma, fault_type);
 		if (error == -EEXIST)
 			goto repeat;
 
-		*pagep = page;
+		*pagep = &folio->page;
 		return error;
 	}
 
-- 
2.34.1

Re: [PATCH 00/21] Folio patches for 5.19

[Nathan Chancellor]

On Fri, Apr 29, 2022 at 08:23:08PM +0100, Matthew Wilcox (Oracle) wrote:
> Andrew, do you want to include these patches in -mm?
> 
>  - Finish the conversion from alloc_pages_vma() to vma_alloc_folio()
>  - Finish converting shrink_page_list() to folios
>  - Start converting shmem from pages to folios (alas, not finished,
>    I have simply run out of time with all the debugging/fixing needed
>    for 5.18)
> 
> Matthew Wilcox (Oracle) (21):
>   shmem: Convert shmem_alloc_hugepage() to use vma_alloc_folio()
>   mm/huge_memory: Convert do_huge_pmd_anonymous_page() to use 
>     vma_alloc_folio()
>   mm: Remove alloc_pages_vma()
>   vmscan: Use folio_mapped() in shrink_page_list()
>   vmscan: Convert the writeback handling in shrink_page_list() to folios
>   swap: Turn get_swap_page() into folio_alloc_swap()
>   swap: Convert add_to_swap() to take a folio
>   vmscan: Convert dirty page handling to folios
>   vmscan: Convert page buffer handling to use folios
>   vmscan: Convert lazy freeing to folios
>   vmscan: Move initialisation of mapping down
>   vmscan: Convert the activate_locked portion of shrink_page_list to
>     folios
>   vmscan: Remove remaining uses of page in shrink_page_list
>   mm/shmem: Use a folio in shmem_unused_huge_shrink
>   mm/swap: Add folio_throttle_swaprate
>   mm/shmem: Convert shmem_add_to_page_cache to take a folio
>   mm/shmem: Turn shmem_should_replace_page into
>     shmem_should_replace_folio
>   mm/shmem: Turn shmem_alloc_page() into shmem_alloc_folio()
>   mm/shmem: Convert shmem_alloc_and_acct_page to use a folio
>   mm/shmem: Convert shmem_getpage_gfp to use a folio
>   mm/shmem: Convert shmem_swapin_page() to shmem_swapin_folio()

This series is now in next-20220503 and causes the following clang
warnings:

mm/shmem.c:1704:7: error: variable 'folio' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
                if (!page) {
                    ^~~~~
mm/shmem.c:1761:6: note: uninitialized use occurs here
        if (folio) {
            ^~~~~
mm/shmem.c:1704:3: note: remove the 'if' if its condition is always false
                if (!page) {
                ^~~~~~~~~~~~
mm/shmem.c:1685:21: note: initialize the variable 'folio' to silence this warning
        struct folio *folio;
                           ^
                            = NULL
mm/shmem.c:2340:8: error: variable 'page' is uninitialized when used here [-Werror,-Wuninitialized]
                if (!page)
                     ^~~~
mm/shmem.c:2321:19: note: initialize the variable 'page' to silence this warning
        struct page *page;
                         ^
                          = NULL
2 errors generated.

The first warning is pretty simple as far as I can tell:

diff --git a/mm/shmem.c b/mm/shmem.c
index 820fde6c2ef6..6a18641a90ff 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1682,7 +1682,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
 	struct page *page;
-	struct folio *folio;
+	struct folio *folio = NULL;
 	swp_entry_t swap;
 	int error;
 

However, I am not sure about the second one. It appears to be caused by
patch 18 in this series. Should it have actually been:

diff --git a/mm/shmem.c b/mm/shmem.c
index 820fde6c2ef6..9e0bd0cffe30 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2337,6 +2337,7 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 
 	if (!*pagep) {
 		ret = -ENOMEM;
+		page = &shmem_alloc_folio(gfp, info, pgoff)->page;
 		if (!page)
 			goto out_unacct_blocks;
 

?

Cheers,
Nathan