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From: | Stefan Weil |
Subject: | Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks |
Date: | Thu, 27 Oct 2011 18:12:00 +0200 |
User-agent: | Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.23) 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
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. Cheers, Stefan
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