ext4: handle redirtying in ext4_bio_write_page()

Since we want to transition transaction commits to use ext4_writepages()
for writing back ordered, add handling of page redirtying into
ext4_bio_write_page(). Also move buffer dirty bit clearing into the same
place other buffer state handling.

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221207112722.22220-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/page-io.c

@@ -482,13 +482,21 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
 			/* A hole? We can safely clear the dirty bit */
 			if (!buffer_mapped(bh))
 				clear_buffer_dirty(bh);
+			/*
+			 * Keeping dirty some buffer we cannot write? Make
+			 * sure to redirty the page. This happens e.g. when
+			 * doing writeout for transaction commit.
+			 */
+			if (buffer_dirty(bh) && !PageDirty(page))
+				redirty_page_for_writepage(wbc, page);
 			if (io->io_bio)
 				ext4_io_submit(io);
 			continue;
 		}
 		if (buffer_new(bh))
 			clear_buffer_new(bh);
 		set_buffer_async_write(bh);
+		clear_buffer_dirty(bh);
 		nr_to_submit++;
 	} while ((bh = bh->b_this_page) != head);
 
@@ -532,7 +540,10 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
 			printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
 			redirty_page_for_writepage(wbc, page);
 			do {
-				clear_buffer_async_write(bh);
+				if (buffer_async_write(bh)) {
+					clear_buffer_async_write(bh);
+					set_buffer_dirty(bh);
+				}
 				bh = bh->b_this_page;
 			} while (bh != head);
 			goto unlock;
@@ -546,7 +557,6 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
 		io_submit_add_bh(io, inode,
 				 bounce_page ? bounce_page : page, bh);
 		nr_submitted++;
-		clear_buffer_dirty(bh);
 	} while ((bh = bh->b_this_page) != head);
 
 unlock: