[PATCH 2/6] mm: Convert __do_fault() to use a folio

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Convert vmf->page to a folio as soon as we're going to use it.  This fixes
a bug if the fault handler returns a tail page with hardware poison;
tail pages have an invalid page->index, so we would fail to unmap the
page from the page tables.  We actually have to unmap the entire folio (or
mapping_evict_folio() will fail), so use unmap_mapping_folio() instead.

This also saves various calls to compound_head() hidden in lock_page(),
put_page(), etc.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Fixes: 793917d997df ("mm/readahead: Add large folio readahead")
Cc: stable@vger.kernel.org
---
 mm/memory.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 1f18ed4a5497..c2ee303ba6b3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4239,6 +4239,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 static vm_fault_t __do_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
+	struct folio *folio;
 	vm_fault_t ret;
 
 	/*
@@ -4267,27 +4268,26 @@ static vm_fault_t __do_fault(struct vm_fault *vmf)
 			    VM_FAULT_DONE_COW)))
 		return ret;
 
+	folio = page_folio(vmf->page);
 	if (unlikely(PageHWPoison(vmf->page))) {
-		struct page *page = vmf->page;
 		vm_fault_t poisonret = VM_FAULT_HWPOISON;
 		if (ret & VM_FAULT_LOCKED) {
-			if (page_mapped(page))
-				unmap_mapping_pages(page_mapping(page),
-						    page->index, 1, false);
-			/* Retry if a clean page was removed from the cache. */
-			if (invalidate_inode_page(page))
+			if (page_mapped(vmf->page))
+				unmap_mapping_folio(folio);
+			/* Retry if a clean folio was removed from the cache. */
+			if (mapping_evict_folio(folio->mapping, folio))
 				poisonret = VM_FAULT_NOPAGE;
-			unlock_page(page);
+			folio_unlock(folio);
 		}
-		put_page(page);
+		folio_put(folio);
 		vmf->page = NULL;
 		return poisonret;
 	}
 
 	if (unlikely(!(ret & VM_FAULT_LOCKED)))
-		lock_page(vmf->page);
+		folio_lock(folio);
 	else
-		VM_BUG_ON_PAGE(!PageLocked(vmf->page), vmf->page);
+		VM_BUG_ON_PAGE(!folio_test_locked(folio), vmf->page);
 
 	return ret;
 }
-- 
2.42.0