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From: | Max Reitz |
Subject: | Re: [Qemu-devel] [PATCH v5 01/11] qcow2: Calculate refcount block entry count |
Date: | Sat, 11 Oct 2014 12:27:51 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.0 |
Am 10.10.2014 um 14:29 schrieb Benoît Canet:
On Fri, Aug 29, 2014 at 11:40:53PM +0200, Max Reitz wrote:The size of a refblock entry is (in theory) variable; calculate therefore the number of entries per refblock and the according bit shift (1 << x == entry count) when opening an image. Signed-off-by: Max Reitz <address@hidden> --- block/qcow2.c | 2 ++ block/qcow2.h | 2 ++ 2 files changed, 4 insertions(+) diff --git a/block/qcow2.c b/block/qcow2.c index f9e045f..172ad00 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -689,6 +689,8 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */s->l2_size = 1 << s->l2_bits; + s->refcount_block_bits = s->cluster_bits - (s->refcount_order - 3);After carefull examination (s->refcount_order - 3) == REFCOUNT_SHIFT. Why not also creating s->refcount_shift and make use of it in order to avoid torturing the mind of the next reader.
I'm sorry. *g*Well, I'm against creating s->refcount_shift, because that name implies you could use it for shifts. But you shouldn't do that, because it may be both negative and positive.
Or simply recall in a comment that there is 2^3 bits in a byte.
I like this more. :-) Max
Best regards Benoît+ s->refcount_block_size = 1 << s->refcount_block_bits; bs->total_sectors = header.size / 512; s->csize_shift = (62 - (s->cluster_bits - 8)); s->csize_mask = (1 << (s->cluster_bits - 8)) - 1; diff --git a/block/qcow2.h b/block/qcow2.h index 6aeb7ea..7c01fb7 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -222,6 +222,8 @@ typedef struct BDRVQcowState { int l2_size; int l1_size; int l1_vm_state_index; + int refcount_block_bits; + int refcount_block_size; int csize_shift; int csize_mask; uint64_t cluster_offset_mask; -- 2.1.0
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