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[Qemu-devel] [PATCH] specs/qcow2: Fix documentation of the compressed cl
From: |
Alberto Garcia |
Subject: |
[Qemu-devel] [PATCH] specs/qcow2: Fix documentation of the compressed cluster descriptor |
Date: |
Tue, 20 Feb 2018 16:15:31 +0200 |
The documentation claims that the cluster descriptor contains the
number of sectors used to store the compressed data, but what it
actually contains is the number of sectors *minus one*.
That can be easily seen in qcow2_decompress_cluster(), that adds one
to the value stored in that field:
nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask) + 1;
Signed-off-by: Alberto Garcia <address@hidden>
---
docs/interop/qcow2.txt | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt
index d7fdb1fee3..b12972be82 100644
--- a/docs/interop/qcow2.txt
+++ b/docs/interop/qcow2.txt
@@ -429,7 +429,8 @@ Compressed Clusters Descriptor (x = 62 - (cluster_bits -
8)):
Bit 0 - x: Host cluster offset. This is usually _not_ aligned to a
cluster boundary!
- x+1 - 61: Compressed size of the images in sectors of 512 bytes
+ x+1 - 61: Size of the compressed data in sectors of 512 bytes,
+ minus one (that is, a value of n here means n+1 sectors).
If a cluster is unallocated, read requests shall read the data from the backing
file (except if bit 0 in the Standard Cluster Descriptor is set). If there is
--
2.11.0
- [Qemu-devel] [PATCH] specs/qcow2: Fix documentation of the compressed cluster descriptor,
Alberto Garcia <=