Description by Jan Kara:
"A lot of older filesystems don't properly flush volatile disk caches
on fsync(2) which can lead to loss of fsynced data after power failure.
This patch makes generic_file_fsync() issue proper cache flush to fix the
problem. Sysadmin can use /sys/devices/.../cache_type to tell the system
it should not send the cache flush."
Signed-off-by: Fabian Frederick <fabf@skynet.be> Suggested-by: Jan Kara <jack@suse.cz> Suggested-by: Christoph Hellwig <hch@infradead.org> Cc: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@infradead.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>