reiserfs: convert writepage to use a folio

Convert the incoming page to a folio and then use it throughout the
writeback path.  This definitely isn't enough to support large folios, but
I don't expect reiserfs to gain support for those before it is removed.

Link: https://lkml.kernel.org/r/20231016201114.1928083-23-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/reiserfs/inode.c

@@ -2507,10 +2507,10 @@ static int map_block_for_writepage(struct inode *inode,
  * start/recovery path as __block_write_full_folio, along with special
  * code to handle reiserfs tails.
  */
-static int reiserfs_write_full_page(struct page *page,
+static int reiserfs_write_full_folio(struct folio *folio,
 				    struct writeback_control *wbc)
 {
-	struct inode *inode = page->mapping->host;
+	struct inode *inode = folio->mapping->host;
 	unsigned long end_index = inode->i_size >> PAGE_SHIFT;
 	int error = 0;
 	unsigned long block;
@@ -2518,7 +2518,7 @@ static int reiserfs_write_full_page(struct page *page,
 	struct buffer_head *head, *bh;
 	int partial = 0;
 	int nr = 0;
-	int checked = PageChecked(page);
+	int checked = folio_test_checked(folio);
 	struct reiserfs_transaction_handle th;
 	struct super_block *s = inode->i_sb;
 	int bh_per_page = PAGE_SIZE / s->s_blocksize;
@@ -2526,47 +2526,46 @@ static int reiserfs_write_full_page(struct page *page,
 
 	/* no logging allowed when nonblocking or from PF_MEMALLOC */
 	if (checked && (current->flags & PF_MEMALLOC)) {
-		redirty_page_for_writepage(wbc, page);
-		unlock_page(page);
+		folio_redirty_for_writepage(wbc, folio);
+		folio_unlock(folio);
 		return 0;
 	}
 
 	/*
-	 * The page dirty bit is cleared before writepage is called, which
+	 * The folio dirty bit is cleared before writepage is called, which
 	 * means we have to tell create_empty_buffers to make dirty buffers
-	 * The page really should be up to date at this point, so tossing
+	 * The folio really should be up to date at this point, so tossing
 	 * in the BH_Uptodate is just a sanity check.
 	 */
-	if (!page_has_buffers(page)) {
-		create_empty_buffers(page, s->s_blocksize,
+	head = folio_buffers(folio);
+	if (!head)
+		head = folio_create_empty_buffers(folio, s->s_blocksize,
 				     (1 << BH_Dirty) | (1 << BH_Uptodate));
-	}
-	head = page_buffers(page);
 
 	/*
-	 * last page in the file, zero out any contents past the
+	 * last folio in the file, zero out any contents past the
 	 * last byte in the file
 	 */
-	if (page->index >= end_index) {
+	if (folio->index >= end_index) {
 		unsigned last_offset;
 
 		last_offset = inode->i_size & (PAGE_SIZE - 1);
-		/* no file contents in this page */
-		if (page->index >= end_index + 1 || !last_offset) {
-			unlock_page(page);
+		/* no file contents in this folio */
+		if (folio->index >= end_index + 1 || !last_offset) {
+			folio_unlock(folio);
 			return 0;
 		}
-		zero_user_segment(page, last_offset, PAGE_SIZE);
+		folio_zero_segment(folio, last_offset, folio_size(folio));
 	}
 	bh = head;
-	block = page->index << (PAGE_SHIFT - s->s_blocksize_bits);
+	block = folio->index << (PAGE_SHIFT - s->s_blocksize_bits);
 	last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
 	/* first map all the buffers, logging any direct items we find */
 	do {
 		if (block > last_block) {
 			/*
 			 * This can happen when the block size is less than
-			 * the page size.  The corresponding bytes in the page
+			 * the folio size.  The corresponding bytes in the folio
 			 * were zero filled above
 			 */
 			clear_buffer_dirty(bh);
@@ -2593,7 +2592,7 @@ static int reiserfs_write_full_page(struct page *page,
 	 * blocks we're going to log
 	 */
 	if (checked) {
-		ClearPageChecked(page);
+		folio_clear_checked(folio);
 		reiserfs_write_lock(s);
 		error = journal_begin(&th, s, bh_per_page + 1);
 		if (error) {
@@ -2602,7 +2601,7 @@ static int reiserfs_write_full_page(struct page *page,
 		}
 		reiserfs_update_inode_transaction(inode);
 	}
-	/* now go through and lock any dirty buffers on the page */
+	/* now go through and lock any dirty buffers on the folio */
 	do {
 		get_bh(bh);
 		if (!buffer_mapped(bh))
@@ -2623,7 +2622,7 @@ static int reiserfs_write_full_page(struct page *page,
 			lock_buffer(bh);
 		} else {
 			if (!trylock_buffer(bh)) {
-				redirty_page_for_writepage(wbc, page);
+				folio_redirty_for_writepage(wbc, folio);
 				continue;
 			}
 		}
@@ -2640,13 +2639,13 @@ static int reiserfs_write_full_page(struct page *page,
 		if (error)
 			goto fail;
 	}
-	BUG_ON(PageWriteback(page));
-	set_page_writeback(page);
-	unlock_page(page);
+	BUG_ON(folio_test_writeback(folio));
+	folio_start_writeback(folio);
+	folio_unlock(folio);
 
 	/*
-	 * since any buffer might be the only dirty buffer on the page,
-	 * the first submit_bh can bring the page out of writeback.
+	 * since any buffer might be the only dirty buffer on the folio,
+	 * the first submit_bh can bring the folio out of writeback.
 	 * be careful with the buffers.
 	 */
 	do {
@@ -2663,10 +2662,10 @@ static int reiserfs_write_full_page(struct page *page,
 done:
 	if (nr == 0) {
 		/*
-		 * if this page only had a direct item, it is very possible for
+		 * if this folio only had a direct item, it is very possible for
 		 * no io to be required without there being an error.  Or,
 		 * someone else could have locked them and sent them down the
-		 * pipe without locking the page
+		 * pipe without locking the folio
 		 */
 		bh = head;
 		do {
@@ -2677,18 +2676,18 @@ static int reiserfs_write_full_page(struct page *page,
 			bh = bh->b_this_page;
 		} while (bh != head);
 		if (!partial)
-			SetPageUptodate(page);
-		end_page_writeback(page);
+			folio_mark_uptodate(folio);
+		folio_end_writeback(folio);
 	}
 	return error;
 
 fail:
 	/*
 	 * catches various errors, we need to make sure any valid dirty blocks
-	 * get to the media.  The page is currently locked and not marked for
+	 * get to the media.  The folio is currently locked and not marked for
 	 * writeback
 	 */
-	ClearPageUptodate(page);
+	folio_clear_uptodate(folio);
 	bh = head;
 	do {
 		get_bh(bh);
@@ -2698,16 +2697,16 @@ static int reiserfs_write_full_page(struct page *page,
 		} else {
 			/*
 			 * clear any dirty bits that might have come from
-			 * getting attached to a dirty page
+			 * getting attached to a dirty folio
 			 */
 			clear_buffer_dirty(bh);
 		}
 		bh = bh->b_this_page;
 	} while (bh != head);
-	SetPageError(page);
-	BUG_ON(PageWriteback(page));
-	set_page_writeback(page);
-	unlock_page(page);
+	folio_set_error(folio);
+	BUG_ON(folio_test_writeback(folio));
+	folio_start_writeback(folio);
+	folio_unlock(folio);
 	do {
 		struct buffer_head *next = bh->b_this_page;
 		if (buffer_async_write(bh)) {
@@ -2728,9 +2727,10 @@ static int reiserfs_read_folio(struct file *f, struct folio *folio)
 
 static int reiserfs_writepage(struct page *page, struct writeback_control *wbc)
 {
-	struct inode *inode = page->mapping->host;
+	struct folio *folio = page_folio(page);
+	struct inode *inode = folio->mapping->host;
 	reiserfs_wait_on_write_block(inode->i_sb);
-	return reiserfs_write_full_page(page, wbc);
+	return reiserfs_write_full_folio(folio, wbc);
 }
 
 static void reiserfs_truncate_failed_write(struct inode *inode)