| Message ID | 1409696709-27623-3-git-send-email-mreitz@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 09/02/2014 04:25 PM, Max Reitz wrote: > A refblock entry may have a different size than 16 bits, it may even be > smaller than a byte. Correct the refcount_block_entries calculation > accordingly. > > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > docs/specs/qcow2.txt | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Eric Blake <eblake@redhat.com> > > diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt > index cfbc8b0..0a878aa 100644 > --- a/docs/specs/qcow2.txt > +++ b/docs/specs/qcow2.txt > @@ -183,7 +183,7 @@ blocks and are exactly one cluster in size. > Given a offset into the image file, the refcount of its cluster can be obtained > as follows: > > - refcount_block_entries = (cluster_size / sizeof(uint16_t)) > + refcount_block_entries = (cluster_size * 8 / refcount_bits) > > refcount_block_index = (offset / cluster_size) % refcount_block_entries > refcount_table_index = (offset / cluster_size) / refcount_block_entries >
On Wed, Sep 03, 2014 at 12:25:08AM +0200, Max Reitz wrote: > A refblock entry may have a different size than 16 bits, it may even be > smaller than a byte. Correct the refcount_block_entries calculation > accordingly. > > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > docs/specs/qcow2.txt | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt index cfbc8b0..0a878aa 100644 --- a/docs/specs/qcow2.txt +++ b/docs/specs/qcow2.txt @@ -183,7 +183,7 @@ blocks and are exactly one cluster in size. Given a offset into the image file, the refcount of its cluster can be obtained as follows: - refcount_block_entries = (cluster_size / sizeof(uint16_t)) + refcount_block_entries = (cluster_size * 8 / refcount_bits) refcount_block_index = (offset / cluster_size) % refcount_block_entries refcount_table_index = (offset / cluster_size) / refcount_block_entries
A refblock entry may have a different size than 16 bits, it may even be smaller than a byte. Correct the refcount_block_entries calculation accordingly. Signed-off-by: Max Reitz <mreitz@redhat.com> --- docs/specs/qcow2.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)