ext2: Fix data integrity writeout issues

ext2: Fix data integrity writeout issues

Ext2 could fail to properly write out inode on fsync(2) due to races
with WB_SYNC_NONE writeback. Several racing fsyncs could also result in
some fsync returning earlier than all metadata buffers were properly
persisted. Finally DIRSYNC handling was not properly persisting all
inode related metadata.

Fix all these issues by using new .sync_inode_metadata method which
makes sure all inode related metadata is written to disk during any
WB_SYNC_ALL writeback.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260727104923.3828017-29-jack@suse.cz
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>