nilfs2: do not call inode_attach_wb() directly

Call mark_buffer_dirty() for segment summary and super root block buffers
on the backing device's page cache, thereby indirectly calling
inode_attach_wb().

Then remove the no longer needed call to inode_attach_wb() in
nilfs_attach_log_writer(), resolving the concern about its layer-violating
use.

Link: https://lkml.kernel.org/r/20240610160029.7673-3-konishi.ryusuke@gmail.comSigned-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/segment.c

@@ -1678,6 +1678,7 @@ static void nilfs_prepare_write_logs(struct list_head *logs, u32 seed)
 	list_for_each_entry(segbuf, logs, sb_list) {
 		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
 				    b_assoc_buffers) {
+			mark_buffer_dirty(bh);
 			if (bh->b_folio == bd_folio)
 				continue;
 			if (bd_folio) {
@@ -1694,6 +1695,7 @@ static void nilfs_prepare_write_logs(struct list_head *logs, u32 seed)
 	/* Prepare to write super root block */
 	bh = NILFS_LAST_SEGBUF(logs)->sb_super_root;
 	if (bh) {
+		mark_buffer_dirty(bh);
 		if (bh->b_folio != bd_folio) {
 			folio_lock(bd_folio);
 			folio_wait_writeback(bd_folio);
@@ -2843,8 +2845,6 @@ int nilfs_attach_log_writer(struct super_block *sb, struct nilfs_root *root)
 	if (!nilfs->ns_writer)
 		return -ENOMEM;
 
-	inode_attach_wb(nilfs->ns_bdev->bd_mapping->host, NULL);
-
 	err = nilfs_segctor_start_thread(nilfs->ns_writer);
 	if (unlikely(err))
 		nilfs_detach_log_writer(sb);