iomap: Convert iomap_write_begin and iomap_write_end to folios

These functions still only work in PAGE_SIZE chunks, but there are
fewer conversions from head to tail pages as a result of this patch.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

fs/iomap/buffered-io.c

@@ -541,9 +541,8 @@ static int iomap_read_folio_sync(loff_t block_start, struct folio *folio,
 
 static int
 __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
-		struct page *page, struct iomap *srcmap)
+		struct folio *folio, struct iomap *srcmap)
 {
-	struct folio *folio = page_folio(page);
 	struct iomap_page *iop = iomap_page_create(inode, folio);
 	loff_t block_size = i_blocksize(inode);
 	loff_t block_start = round_down(pos, block_size);
@@ -583,12 +582,14 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
 	return 0;
 }
 
-static int
-iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
-		struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
+static int iomap_write_begin(struct inode *inode, loff_t pos, size_t len,
+		unsigned flags, struct folio **foliop, struct iomap *iomap,
+		struct iomap *srcmap)
 {
 	const struct iomap_page_ops *page_ops = iomap->page_ops;
+	struct folio *folio;
 	struct page *page;
+	unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
 	int status = 0;
 
 	BUG_ON(pos + len > iomap->offset + iomap->length);
@@ -604,30 +605,31 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
 			return status;
 	}
 
-	page = grab_cache_page_write_begin(inode->i_mapping, pos >> PAGE_SHIFT,
-			AOP_FLAG_NOFS);
-	if (!page) {
+	folio = __filemap_get_folio(inode->i_mapping, pos >> PAGE_SHIFT, fgp,
+			mapping_gfp_mask(inode->i_mapping));
+	if (!folio) {
 		status = -ENOMEM;
 		goto out_no_page;
 	}
 
+	page = folio_file_page(folio, pos >> PAGE_SHIFT);
 	if (srcmap->type == IOMAP_INLINE)
 		iomap_read_inline_data(inode, page, srcmap);
 	else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
 		status = __block_write_begin_int(page, pos, len, NULL, srcmap);
 	else
-		status = __iomap_write_begin(inode, pos, len, flags, page,
+		status = __iomap_write_begin(inode, pos, len, flags, folio,
 				srcmap);
 
 	if (unlikely(status))
 		goto out_unlock;
 
-	*pagep = page;
+	*foliop = folio;
 	return 0;
 
 out_unlock:
-	unlock_page(page);
-	put_page(page);
+	folio_unlock(folio);
+	folio_put(folio);
 	iomap_write_failed(inode, pos, len);
 
 out_no_page:
@@ -637,11 +639,10 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
 }
 
 static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
-		size_t copied, struct page *page)
+		size_t copied, struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	struct iomap_page *iop = to_iomap_page(folio);
-	flush_dcache_page(page);
+	flush_dcache_folio(folio);
 
 	/*
 	 * The blocks that were entirely written will now be uptodate, so we
@@ -654,10 +655,10 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 	 * uptodate page as a zero-length write, and force the caller to redo
 	 * the whole thing.
 	 */
-	if (unlikely(copied < len && !PageUptodate(page)))
+	if (unlikely(copied < len && !folio_test_uptodate(folio)))
 		return 0;
 	iomap_set_range_uptodate(folio, iop, offset_in_folio(folio, pos), len);
-	__set_page_dirty_nobuffers(page);
+	filemap_dirty_folio(inode->i_mapping, folio);
 	return copied;
 }
 
@@ -680,9 +681,10 @@ static size_t iomap_write_end_inline(struct inode *inode, struct page *page,
 
 /* Returns the number of bytes copied.  May be 0.  Cannot be an errno. */
 static size_t iomap_write_end(struct inode *inode, loff_t pos, size_t len,
-		size_t copied, struct page *page, struct iomap *iomap,
+		size_t copied, struct folio *folio, struct iomap *iomap,
 		struct iomap *srcmap)
 {
+	struct page *page = folio_file_page(folio, pos / PAGE_SIZE);
 	const struct iomap_page_ops *page_ops = iomap->page_ops;
 	loff_t old_size = inode->i_size;
 	size_t ret;
@@ -693,7 +695,7 @@ static size_t iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 		ret = block_write_end(NULL, inode->i_mapping, pos, len, copied,
 				page, NULL);
 	} else {
-		ret = __iomap_write_end(inode, pos, len, copied, page);
+		ret = __iomap_write_end(inode, pos, len, copied, folio);
 	}
 
 	/*
@@ -705,13 +707,13 @@ static size_t iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 		i_size_write(inode, pos + ret);
 		iomap->flags |= IOMAP_F_SIZE_CHANGED;
 	}
-	unlock_page(page);
+	folio_unlock(folio);
 
 	if (old_size < pos)
 		pagecache_isize_extended(inode, old_size, pos);
 	if (page_ops && page_ops->page_done)
 		page_ops->page_done(inode, pos, ret, page, iomap);
-	put_page(page);
+	folio_put(folio);
 
 	if (ret < len)
 		iomap_write_failed(inode, pos, len);
@@ -727,6 +729,7 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 	ssize_t written = 0;
 
 	do {
+		struct folio *folio;
 		struct page *page;
 		unsigned long offset;	/* Offset into pagecache page */
 		unsigned long bytes;	/* Bytes to write to page */
@@ -750,18 +753,19 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 			break;
 		}
 
-		status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap,
+		status = iomap_write_begin(inode, pos, bytes, 0, &folio, iomap,
 				srcmap);
 		if (unlikely(status))
 			break;
 
+		page = folio_file_page(folio, pos / PAGE_SIZE);
 		if (mapping_writably_mapped(inode->i_mapping))
 			flush_dcache_page(page);
 
 		copied = copy_page_from_iter_atomic(page, offset, bytes, i);
 
-		status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
-				srcmap);
+		status = iomap_write_end(inode, pos, bytes, copied, folio,
+				iomap, srcmap);
 
 		if (unlikely(copied != status))
 			iov_iter_revert(i, copied - status);
@@ -825,14 +829,14 @@ iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 	do {
 		unsigned long offset = offset_in_page(pos);
 		unsigned long bytes = min_t(loff_t, PAGE_SIZE - offset, length);
-		struct page *page;
+		struct folio *folio;
 
 		status = iomap_write_begin(inode, pos, bytes,
-				IOMAP_WRITE_F_UNSHARE, &page, iomap, srcmap);
+				IOMAP_WRITE_F_UNSHARE, &folio, iomap, srcmap);
 		if (unlikely(status))
 			return status;
 
-		status = iomap_write_end(inode, pos, bytes, bytes, page, iomap,
+		status = iomap_write_end(inode, pos, bytes, bytes, folio, iomap,
 				srcmap);
 		if (WARN_ON_ONCE(status == 0))
 			return -EIO;
@@ -871,19 +875,19 @@ EXPORT_SYMBOL_GPL(iomap_file_unshare);
 static s64 iomap_zero(struct inode *inode, loff_t pos, u64 length,
 		struct iomap *iomap, struct iomap *srcmap)
 {
-	struct page *page;
+	struct folio *folio;
 	int status;
 	unsigned offset = offset_in_page(pos);
 	unsigned bytes = min_t(u64, PAGE_SIZE - offset, length);
 
-	status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap, srcmap);
+	status = iomap_write_begin(inode, pos, bytes, 0, &folio, iomap, srcmap);
 	if (status)
 		return status;
 
-	zero_user(page, offset, bytes);
-	mark_page_accessed(page);
+	zero_user(folio_file_page(folio, pos / PAGE_SIZE), offset, bytes);
+	folio_mark_accessed(folio);
 
-	return iomap_write_end(inode, pos, bytes, bytes, page, iomap, srcmap);
+	return iomap_write_end(inode, pos, bytes, bytes, folio, iomap, srcmap);
 }
 
 static loff_t iomap_zero_range_actor(struct inode *inode, loff_t pos,