truncate,shmem: Add truncate_inode_folio()

Convert all callers of truncate_inode_page() to call
truncate_inode_folio() instead, and move the declaration to mm/internal.h.
Move the assertion that the caller is not passing in a tail page to
generic_error_remove_page().  We can't entirely remove the struct page
from the callers yet because the page pointer in the pvec might be a
shadow/dax/swap entry instead of actually a page.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

include/linux/mm.h

@@ -1859,7 +1859,6 @@ extern void truncate_pagecache(struct inode *inode, loff_t new);
 extern void truncate_setsize(struct inode *inode, loff_t newsize);
 void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to);
 void truncate_pagecache_range(struct inode *inode, loff_t offset, loff_t end);
-int truncate_inode_page(struct address_space *mapping, struct page *page);
 int generic_error_remove_page(struct address_space *mapping, struct page *page);
 int invalidate_inode_page(struct page *page);
 

mm/internal.h

@@ -92,6 +92,7 @@ static inline void force_page_cache_readahead(struct address_space *mapping,
 
 unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
 		pgoff_t end, struct pagevec *pvec, pgoff_t *indices);
+int truncate_inode_folio(struct address_space *mapping, struct folio *folio);
 
 /**
  * folio_evictable - Test whether a folio is evictable.

mm/shmem.c

@@ -950,7 +950,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 			index += folio_nr_pages(folio) - 1;
 
 			if (!unfalloc || !folio_test_uptodate(folio))
-				truncate_inode_page(mapping, &folio->page);
+				truncate_inode_folio(mapping, folio);
 			folio_unlock(folio);
 		}
 		pagevec_remove_exceptionals(&pvec);
@@ -1027,7 +1027,8 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 				}
 				VM_BUG_ON_PAGE(PageWriteback(page), page);
 				if (shmem_punch_compound(page, start, end))
-					truncate_inode_page(mapping, page);
+					truncate_inode_folio(mapping,
+							     page_folio(page));
 				else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 					/* Wipe the page and don't get stuck */
 					clear_highpage(page);

mm/truncate.c

@@ -218,12 +218,9 @@ invalidate_complete_page(struct address_space *mapping, struct page *page)
 	return ret;
 }
 
-int truncate_inode_page(struct address_space *mapping, struct page *page)
+int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
-	VM_BUG_ON_PAGE(PageTail(page), page);
-
-	if (page->mapping != mapping)
+	if (folio->mapping != mapping)
 		return -EIO;
 
 	truncate_cleanup_folio(folio);
@@ -236,6 +233,8 @@ int truncate_inode_page(struct address_space *mapping, struct page *page)
  */
 int generic_error_remove_page(struct address_space *mapping, struct page *page)
 {
+	VM_BUG_ON_PAGE(PageTail(page), page);
+
 	if (!mapping)
 		return -EINVAL;
 	/*
@@ -244,7 +243,7 @@ int generic_error_remove_page(struct address_space *mapping, struct page *page)
 	 */
 	if (!S_ISREG(mapping->host->i_mode))
 		return -EIO;
-	return truncate_inode_page(mapping, page);
+	return truncate_inode_folio(mapping, page_folio(page));
 }
 EXPORT_SYMBOL(generic_error_remove_page);
 
@@ -395,18 +394,20 @@ void truncate_inode_pages_range(struct address_space *mapping,
 
 		for (i = 0; i < pagevec_count(&pvec); i++) {
 			struct page *page = pvec.pages[i];
+			struct folio *folio;
 
 			/* We rely upon deletion not changing page->index */
 			index = indices[i];
 
 			if (xa_is_value(page))
 				continue;
+			folio = page_folio(page);
 
-			lock_page(page);
-			WARN_ON(page_to_index(page) != index);
-			wait_on_page_writeback(page);
-			truncate_inode_page(mapping, page);
-			unlock_page(page);
+			folio_lock(folio);
+			VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
+			folio_wait_writeback(folio);
+			truncate_inode_folio(mapping, folio);
+			folio_unlock(folio);
 		}
 		truncate_exceptional_pvec_entries(mapping, &pvec, indices);
 		pagevec_release(&pvec);