Does syncfs wait until disc write finished?

Question

Does the new syncfs system call wait for disc write completion before returning, like in case of fsync? Also, if after modifying file, is calling syncfs for this file descriptor also update the containing directoy entry?

Answer 1

syncfs writes out all dirty pages from the superblock on down. Disks may have write caching, so this does not guarantee that all data has been saved. You could, for example, turn off power without still calling shutdown.