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Re: [Qemu-trivial] [Qemu-devel] [PATCH] Teach block/vdi about "discarded
Re: [Qemu-trivial] [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks
Thu, 27 Oct 2011 18:12:00 +0200
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:220.127.116.11) Gecko/20110921 Thunderbird/3.1.15
Am 27.10.2011 10:53, schrieb Kevin Wolf:
Am 26.10.2011 21:51, schrieb Eric Sunshine:
An entry in the VDI block map will hold an offset to the actual block if
the block is allocated, or one of two specially-interpreted values if
not allocated. Using VirtualBox terminology, value VDI_IMAGE_BLOCK_FREE
(0xffffffff) represents a never-allocated block (semantically arbitrary
content). VDI_IMAGE_BLOCK_ZERO (0xfffffffe) represents a "discarded"
block (semantically zero-filled). block/vdi knows only about
VDI_IMAGE_BLOCK_FREE. Teach it about VDI_IMAGE_BLOCK_ZERO.
Signed-off-by: Eric Sunshine <address@hidden>
Thanks, applied to the block branch.
Kevin, I don't want to block improvements. Nevertheless
I'd like to see a small modification in this patch:
both #defines should be implemented without a type cast.
Please change them or wait until Eric sends an update.
My favorite is this:
#define VDI_UNALLOCATED UINT32_MAX
#define VDI_DISCARD (VDI_UNALLOCATED - 1)
This would also be ok:
#define VDI_UNALLOCATED 0xffffffffU
#define VDI_DISCARD 0xfffffffeU
Using the macro names and the definitions (with type cast)
from the original VirtualBox code would also be ok.