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block: flush backing_hd in the right place

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The backing device is only modified from bdrv_commit.  So instead of
flushing it every time bdrv_flush is called for the front-end device
only flush it after we're written data to it in bdrv_commit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Christoph Hellwig 2010-01-12 13:49:23 +01:00 committed by Anthony Liguori
parent 2da69c8d12
commit 3f5075ae63
1 changed files with 7 additions and 10 deletions
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17
block.c
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@ -594,6 +594,12 @@ int bdrv_commit(BlockDriverState *bs)
if (drv->bdrv_make_empty)
return drv->bdrv_make_empty(bs);
/*
* Make sure all data we wrote to the backing device is actually
* stable on disk.
*/
if (bs->backing_hd)
bdrv_flush(bs->backing_hd);
return 0;
}
@ -1115,12 +1121,8 @@ const char *bdrv_get_device_name(BlockDriverState *bs)
void bdrv_flush(BlockDriverState *bs)
{
if (!bs->drv)
return;
if (bs->drv->bdrv_flush)
if (bs->drv && bs->drv->bdrv_flush)
bs->drv->bdrv_flush(bs);
if (bs->backing_hd)
bdrv_flush(bs->backing_hd);
}
void bdrv_flush_all(void)
@ -1797,11 +1799,6 @@ BlockDriverAIOCB *bdrv_aio_flush(BlockDriverState *bs,
if (!drv)
return NULL;
/*
* Note that unlike bdrv_flush the driver is reponsible for flushing a
* backing image if it exists.
*/
return drv->bdrv_aio_flush(bs, cb, opaque);
}