ext4: Track metadata bhs in fs-private inode part

Track metadata bhs for an inode in fs-private part of the inode. We need
the tracking only for nojournal mode so this is somewhat wasteful. We
can relatively easily make the mapping_metadata_bhs struct dynamically
allocated similarly to how we treat jbd2_inode but let's leave that for
ext4 specific series once the dust settles a bit.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260326095354.16340-82-jack@suse.cz
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: jankara

fs/ext4/ext4.h

@@ -1121,6 +1121,7 @@ struct ext4_inode_info {
 	struct rw_semaphore i_data_sem;
 	struct inode vfs_inode;
 	struct jbd2_inode *jinode;
+	struct mapping_metadata_bhs i_metadata_bhs;
 
 	/*
 	 * File creation time. Its function is same as that of

fs/ext4/ext4_jbd2.c

@@ -390,7 +390,8 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
 		}
 	} else {
 		if (inode)
-			mark_buffer_dirty_inode(bh, inode);
+			mmb_mark_buffer_dirty(bh,
+					      &EXT4_I(inode)->i_metadata_bhs);
 		else
 			mark_buffer_dirty(bh);
 		if (inode && inode_needs_sync(inode)) {

fs/ext4/fsync.c

@@ -68,7 +68,7 @@ static int ext4_sync_parent(struct inode *inode)
 		 * through ext4_evict_inode()) and so we are safe to flush
 		 * metadata blocks and the inode.
 		 */
-		ret = sync_mapping_buffers(inode->i_mapping);
+		ret = mmb_sync(&EXT4_I(inode)->i_metadata_bhs);
 		if (ret)
 			break;
 		ret = sync_inode_metadata(inode, 1);
@@ -85,7 +85,8 @@ static int ext4_fsync_nojournal(struct file *file, loff_t start, loff_t end,
 	struct inode *inode = file->f_inode;
 	int ret;
 
-	ret = generic_buffers_fsync_noflush(file, start, end, datasync);
+	ret = mmb_fsync_noflush(file, &EXT4_I(inode)->i_metadata_bhs,
+				start, end, datasync);
 	if (!ret)
 		ret = ext4_sync_parent(inode);
 	if (test_opt(inode->i_sb, BARRIER))

fs/ext4/inode.c

@@ -187,7 +187,7 @@ void ext4_evict_inode(struct inode *inode)
 		truncate_inode_pages_final(&inode->i_data);
 		/* Avoid mballoc special inode which has no proper iops */
 		if (!EXT4_SB(inode->i_sb)->s_journal)
-			sync_mapping_buffers(&inode->i_data);
+			mmb_sync(&EXT4_I(inode)->i_metadata_bhs);
 		goto no_delete;
 	}
 
@@ -3436,7 +3436,7 @@ static bool ext4_inode_datasync_dirty(struct inode *inode)
 	}
 
 	/* Any metadata buffers to write? */
-	if (mmb_has_buffers(&inode->i_mapping->i_metadata_bhs))
+	if (mmb_has_buffers(&EXT4_I(inode)->i_metadata_bhs))
 		return true;
 	return inode_state_read_once(inode) & I_DIRTY_DATASYNC;
 }

fs/ext4/super.c

@@ -1428,6 +1428,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 	INIT_WORK(&ei->i_rsv_conversion_work, ext4_end_io_rsv_work);
 	ext4_fc_init_inode(&ei->vfs_inode);
 	spin_lock_init(&ei->i_fc_lock);
+	mmb_init(&ei->i_metadata_bhs, &ei->vfs_inode.i_data);
 	return &ei->vfs_inode;
 }
 
@@ -1525,7 +1526,7 @@ void ext4_clear_inode(struct inode *inode)
 {
 	ext4_fc_del(inode);
 	if (!EXT4_SB(inode->i_sb)->s_journal)
-		invalidate_inode_buffers(inode);
+		mmb_invalidate(&EXT4_I(inode)->i_metadata_bhs);
 	clear_inode(inode);
 	ext4_discard_preallocations(inode);
 	ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS);