On Mon, 09/01 13:11, Benoît Canet wrote:
> The Monday 01 Sep 2014 à 18:52:48 (+0800), Jun Li wrote :
> > When every item of refcount block is NULL, free refcount block and reset the
> > corresponding item of refcount table with NULL.
> >
> > Signed-off-by: Jun Li <address@hidden>
> > ---
> >
> > The v2 do following change to modify some potential issue.
> >
> > +------- Here should start from "0".
> > |
> > for (k = 0; k < refcount_block_entries; k++) {
> > if (refcount_block[k] != cpu_to_be16(0)) {
> > ... | |
> > } | |
> > } | +---- Using "0" is more safe.
> > |
> > +-------- This should be "k" not "++k".
> > ---
> > block/qcow2-refcount.c | 31 +++++++++++++++++++++++++++++++
> > 1 file changed, 31 insertions(+)
> >
> > diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> > index 43665b8..63f36e6 100644
> > --- a/block/qcow2-refcount.c
> > +++ b/block/qcow2-refcount.c
> > @@ -586,6 +586,37 @@ static int QEMU_WARN_UNUSED_RESULT
> > update_refcount(BlockDriverState *bs,
> > if (refcount == 0 && s->discard_passthrough[type]) {
> > update_refcount_discard(bs, cluster_offset, s->cluster_size);
> > }
> > +
> > + /* When refcount block is NULL, update refcount table */
> > + if (block_index == 0) {
> > + int k = block_index;
> > + int refcount_block_entries = s->cluster_size /
> > sizeof(uint16_t);
> > + for (k = 0; k < refcount_block_entries; k++) {
> > + if (refcount_block[k] != cpu_to_be16(0)) {
> > + break;
> > + }
> > + }
> > +
> > + if (k == refcount_block_entries) {
> > + qemu_vfree(refcount_block);
> > + /* update refcount table */
> > + unsigned int refcount_table_index;
> > + uint64_t data64 = cpu_to_be64(0);
> > + refcount_table_index = cluster_index >> (s->cluster_bits -
> > + REFCOUNT_SHIFT);
> > + ret = bdrv_pwrite_sync(bs->file,
> > + s->refcount_table_offset +
> > + refcount_table_index *
> > + sizeof(uint64_t),
> > + &data64, sizeof(data64));
> > + if (ret < 0) {
> > + goto fail;
> > + }
> > +
>
> > + s->refcount_table[refcount_table_index] = data64;
>
> Shouldn't the in memory version be be in cpu order ? like
> s->refcount_table[refcount_table_index] = 0;
I don't think so. See following:
(gdb) p sizeof(s->refcount_table[0])
$5 = 8
(gdb) p sizeof(s->refcount_table[1])
$6 = 8
(gdb) p sizeof(0)
$7 = 4
So I think here is right. Thank you for sharing Max's patch(qcow2: Drop
REFCOUNT_SHIFT) with me. I find this patch has been reviewed, but it has not
been merged. Maybe I will modify my realization after this patch merged.
Thanks again.
Jun Li
>
> Best regards
>
> Benoît
> > +
> > + }
> > + }
> > }
> >
> > ret = 0;
> > --
> > 1.9.3
> >
> >
