[Qemu-devel] [PATCH 2/4] block: use fdatasync instead of fsync

[Christoph Hellwig <hch@lst.de>]

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 use fdatasync instead of fsync to implement
the flush operations.


Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: qemu/block/cow.c
===================================================================
--- qemu.orig/block/cow.c	2009-06-07 16:18:21.942938914 -0300
+++ qemu/block/cow.c	2009-08-31 16:49:55.509043084 -0300
@@ -258,7 +258,7 @@ static int cow_create(const char *filena
 static void cow_flush(BlockDriverState *bs)
 {
     BDRVCowState *s = bs->opaque;
-    fsync(s->fd);
+    fdatasync(s->fd);
 }
 
 static QEMUOptionParameter cow_create_options[] = {
Index: qemu/block/raw-posix.c
===================================================================
--- qemu.orig/block/raw-posix.c	2009-08-29 14:17:23.039370199 -0300
+++ qemu/block/raw-posix.c	2009-08-31 16:49:55.513071598 -0300
@@ -723,7 +723,7 @@ static int raw_create(const char *filena
 static void raw_flush(BlockDriverState *bs)
 {
     BDRVRawState *s = bs->opaque;
-    fsync(s->fd);
+    fdatasync(s->fd);
 }