fsync() causes all modified data and attributes of
fd to be moved to a permanent storage device. This normally results in all in-core modified copies of buffers for the associated file to be written to a disk.
fsync() should be used by programs that require a file to be in a known state, for example, in building a simple transaction facility.
fsync_range() causes all modified data starting at
start for length
length of
fd to be written to permanent storage. Note that
fsync_range() requires that the file
fd must be open for writing.
fsync_range() may flush the file data in one of two manners:
FDATASYNC
Synchronize the file data and sufficient meta-data to retrieve the data for the specified range.
FFILESYNC
Synchronize all modified file data and meta-data for the specified range.
By default,
fsync_range() does not flush disk caches, assuming that storage media are able to ensure completed writes are transfered to media. The
FDISKSYNC flag may be included in the
how parameter to trigger flushing of all disk caches for the file.
If the
length parameter is zero,
fsync_range() will synchronize all of the file data.