tree 522dacdca726cc3b8bc321e70791d03a3b543e72
parent e900a7b748316b5b5a98e41dde36a0cb8e15be5f
author Christoph Hellwig <hch@lst.de> 1252083692 +0200
committer Anthony Liguori <aliguori@us.ibm.com> 1252682386 -0500

block: use fdatasync instead of fsync if possible

If we are flushing the caches for our image files we only care about the
data (including the metadata required for accessing it) but not things
like timestamp updates.  So try to use fdatasync instead of fsync to
implement the flush operations.

Unfortunately many operating systems still do not support fdatasync,
so we add a qemu_fdatasync wrapper that uses fdatasync if available
as per the _POSIX_SYNCHRONIZED_IO feature macro or fsync otherwise.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>