| Message ID | 20100112181306.GA1849@lst.de |
|---|---|
| State | New |
| Headers | show |
Am 12.01.2010 19:13, schrieb Christoph Hellwig: > 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. > > Also flush the frontend image if we have a make_empty method that > possibly writes to it. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > > Index: qemu/block.c > =================================================================== > --- qemu.orig/block.c 2010-01-12 19:08:07.363003775 +0100 > +++ qemu/block.c 2010-01-12 19:09:10.836255948 +0100 > @@ -589,6 +589,7 @@ int bdrv_commit(BlockDriverState *bs) > BlockDriver *drv = bs->drv; > int64_t i, total_sectors; > int n, j; > + int ret = 0; > unsigned char sector[512]; > > if (!drv) > @@ -620,10 +621,18 @@ int bdrv_commit(BlockDriverState *bs) > } > } > > - if (drv->bdrv_make_empty) > - return drv->bdrv_make_empty(bs); > + if (drv->bdrv_make_empty) { > + ret = drv->bdrv_make_empty(bs); > + bdrv_flush(bs); > + } Indentation is off here (but it already was before the patch). The logic looks good to me now. Kevin
Index: qemu/block.c =================================================================== --- qemu.orig/block.c 2010-01-12 19:08:07.363003775 +0100 +++ qemu/block.c 2010-01-12 19:09:10.836255948 +0100 @@ -589,6 +589,7 @@ int bdrv_commit(BlockDriverState *bs) BlockDriver *drv = bs->drv; int64_t i, total_sectors; int n, j; + int ret = 0; unsigned char sector[512]; if (!drv) @@ -620,10 +621,18 @@ int bdrv_commit(BlockDriverState *bs) } } - if (drv->bdrv_make_empty) - return drv->bdrv_make_empty(bs); + if (drv->bdrv_make_empty) { + ret = drv->bdrv_make_empty(bs); + bdrv_flush(bs); + } - return 0; + /* + * 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 ret; } static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset, @@ -1124,12 +1133,8 @@ const char *bdrv_get_device_name(BlockDr 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) @@ -1806,11 +1811,6 @@ BlockDriverAIOCB *bdrv_aio_flush(BlockDr 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); }
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. Also flush the frontend image if we have a make_empty method that possibly writes to it. Signed-off-by: Christoph Hellwig <hch@lst.de>