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block: clarify the meaning of BDRV_O_NOCACHE

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Change BDRV_O_NOCACHE to only imply bypassing the host OS file cache,
but no writeback semantics.  All existing callers are changed to also
specify BDRV_O_CACHE_WB to give them writeback semantics.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Christoph Hellwig 2011-05-17 18:04:06 +02:00 • committed by Kevin Wolf
parent 69c38b8fce
commit a659979328
7 changed files with 13 additions and 19 deletions
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8
block.c
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@ -439,13 +439,7 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename,
bs->drv = drv;
bs->opaque = qemu_mallocz(drv->instance_size);
/*
* Yes, BDRV_O_NOCACHE aka O_DIRECT means we have to present a
* write cache to the guest. We do need the fdatasync to flush
* out transactions for block allocations, and we maybe have a
* volatile write cache in our backing device to deal with.
*/
if (flags & (BDRV_O_CACHE_WB|BDRV_O_NOCACHE))
if (flags & BDRV_O_CACHE_WB)
bs->enable_write_cache = 1;
/*