khugepaged: remove hpage from collapse_file()

Use new_folio throughout where we had been using hpage.

Link: https://lkml.kernel.org/r/20240403171838.1445826-6-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/trace/events/huge_memory.h

@@ -207,10 +207,10 @@ TRACE_EVENT(mm_khugepaged_scan_file,
 );
 
 TRACE_EVENT(mm_khugepaged_collapse_file,
-	TP_PROTO(struct mm_struct *mm, struct page *hpage, pgoff_t index,
+	TP_PROTO(struct mm_struct *mm, struct folio *new_folio, pgoff_t index,
 			bool is_shmem, unsigned long addr, struct file *file,
 			int nr, int result),
-	TP_ARGS(mm, hpage, index, addr, is_shmem, file, nr, result),
+	TP_ARGS(mm, new_folio, index, addr, is_shmem, file, nr, result),
 	TP_STRUCT__entry(
 		__field(struct mm_struct *, mm)
 		__field(unsigned long, hpfn)
@@ -224,7 +224,7 @@ TRACE_EVENT(mm_khugepaged_collapse_file,
 
 	TP_fast_assign(
 		__entry->mm = mm;
-		__entry->hpfn = hpage ? page_to_pfn(hpage) : -1;
+		__entry->hpfn = new_folio ? folio_pfn(new_folio) : -1;
 		__entry->index = index;
 		__entry->addr = addr;
 		__entry->is_shmem = is_shmem;

mm/khugepaged.c

@@ -1780,30 +1780,27 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 			 struct collapse_control *cc)
 {
 	struct address_space *mapping = file->f_mapping;
-	struct page *hpage;
 	struct page *page;
-	struct page *tmp;
+	struct page *tmp, *dst;
 	struct folio *folio, *new_folio;
 	pgoff_t index = 0, end = start + HPAGE_PMD_NR;
 	LIST_HEAD(pagelist);
 	XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
 	int nr_none = 0, result = SCAN_SUCCEED;
 	bool is_shmem = shmem_file(file);
-	int nr = 0;
 
 	VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
 	VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
 
 	result = alloc_charge_folio(&new_folio, mm, cc);
-	hpage = &new_folio->page;
 	if (result != SCAN_SUCCEED)
 		goto out;
 
-	__SetPageLocked(hpage);
+	__folio_set_locked(new_folio);
 	if (is_shmem)
-		__SetPageSwapBacked(hpage);
-	hpage->index = start;
-	hpage->mapping = mapping;
+		__folio_set_swapbacked(new_folio);
+	new_folio->index = start;
+	new_folio->mapping = mapping;
 
 	/*
 	 * Ensure we have slots for all the pages in the range.  This is
@@ -2036,20 +2033,24 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 	 * The old pages are locked, so they won't change anymore.
 	 */
 	index = start;
+	dst = folio_page(new_folio, 0);
 	list_for_each_entry(page, &pagelist, lru) {
 		while (index < page->index) {
-			clear_highpage(hpage + (index % HPAGE_PMD_NR));
+			clear_highpage(dst);
 			index++;
+			dst++;
 		}
-		if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR), page) > 0) {
+		if (copy_mc_highpage(dst, page) > 0) {
 			result = SCAN_COPY_MC;
 			goto rollback;
 		}
 		index++;
+		dst++;
 	}
 	while (index < end) {
-		clear_highpage(hpage + (index % HPAGE_PMD_NR));
+		clear_highpage(dst);
 		index++;
+		dst++;
 	}
 
 	if (nr_none) {
@@ -2077,16 +2078,17 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 		}
 
 		/*
-		 * If userspace observed a missing page in a VMA with a MODE_MISSING
-		 * userfaultfd, then it might expect a UFFD_EVENT_PAGEFAULT for that
-		 * page. If so, we need to roll back to avoid suppressing such an
-		 * event. Since wp/minor userfaultfds don't give userspace any
-		 * guarantees that the kernel doesn't fill a missing page with a zero
-		 * page, so they don't matter here.
+		 * If userspace observed a missing page in a VMA with
+		 * a MODE_MISSING userfaultfd, then it might expect a
+		 * UFFD_EVENT_PAGEFAULT for that page. If so, we need to
+		 * roll back to avoid suppressing such an event. Since
+		 * wp/minor userfaultfds don't give userspace any
+		 * guarantees that the kernel doesn't fill a missing
+		 * page with a zero page, so they don't matter here.
 		 *
-		 * Any userfaultfds registered after this point will not be able to
-		 * observe any missing pages due to the previously inserted retry
-		 * entries.
+		 * Any userfaultfds registered after this point will
+		 * not be able to observe any missing pages due to the
+		 * previously inserted retry entries.
 		 */
 		vma_interval_tree_foreach(vma, &mapping->i_mmap, start, end) {
 			if (userfaultfd_missing(vma)) {
@@ -2111,33 +2113,32 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 		xas_lock_irq(&xas);
 	}
 
-	folio = page_folio(hpage);
-	nr = folio_nr_pages(folio);
 	if (is_shmem)
-		__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
+		__lruvec_stat_mod_folio(new_folio, NR_SHMEM_THPS, HPAGE_PMD_NR);
 	else
-		__lruvec_stat_mod_folio(folio, NR_FILE_THPS, nr);
+		__lruvec_stat_mod_folio(new_folio, NR_FILE_THPS, HPAGE_PMD_NR);
 
 	if (nr_none) {
-		__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr_none);
+		__lruvec_stat_mod_folio(new_folio, NR_FILE_PAGES, nr_none);
 		/* nr_none is always 0 for non-shmem. */
-		__lruvec_stat_mod_folio(folio, NR_SHMEM, nr_none);
+		__lruvec_stat_mod_folio(new_folio, NR_SHMEM, nr_none);
 	}
 
 	/*
-	 * Mark hpage as uptodate before inserting it into the page cache so
-	 * that it isn't mistaken for an fallocated but unwritten page.
+	 * Mark new_folio as uptodate before inserting it into the
+	 * page cache so that it isn't mistaken for an fallocated but
+	 * unwritten page.
 	 */
-	folio_mark_uptodate(folio);
-	folio_ref_add(folio, HPAGE_PMD_NR - 1);
+	folio_mark_uptodate(new_folio);
+	folio_ref_add(new_folio, HPAGE_PMD_NR - 1);
 
 	if (is_shmem)
-		folio_mark_dirty(folio);
-	folio_add_lru(folio);
+		folio_mark_dirty(new_folio);
+	folio_add_lru(new_folio);
 
 	/* Join all the small entries into a single multi-index entry. */
 	xas_set_order(&xas, start, HPAGE_PMD_ORDER);
-	xas_store(&xas, folio);
+	xas_store(&xas, new_folio);
 	WARN_ON_ONCE(xas_error(&xas));
 	xas_unlock_irq(&xas);
 
@@ -2148,7 +2149,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 	retract_page_tables(mapping, start);
 	if (cc && !cc->is_khugepaged)
 		result = SCAN_PTE_MAPPED_HUGEPAGE;
-	folio_unlock(folio);
+	folio_unlock(new_folio);
 
 	/*
 	 * The collapse has succeeded, so free the old pages.
@@ -2193,13 +2194,13 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 		smp_mb();
 	}
 
-	hpage->mapping = NULL;
+	new_folio->mapping = NULL;
 
-	unlock_page(hpage);
-	put_page(hpage);
+	folio_unlock(new_folio);
+	folio_put(new_folio);
 out:
 	VM_BUG_ON(!list_empty(&pagelist));
-	trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result);
+	trace_mm_khugepaged_collapse_file(mm, new_folio, index, is_shmem, addr, file, HPAGE_PMD_NR, result);
 	return result;
 }