From: Greg Kurz <gkurz@linux.vnet.ibm.com>
To: Jun Li <junmuzi@gmail.com>
Cc: kwolf@redhat.com, juli@redhat.com, famz@redhat.com,
qemu-devel@nongnu.org, stefanha@redhat.com
Subject: Re: [Qemu-devel] [PATCH v2] qcow2: add update refcount table realization for update_refcount
Date: Tue, 2 Sep 2014 19:12:27 +0200 [thread overview]
Message-ID: <20140902191227.7f07b4f0@bahia.local> (raw)
In-Reply-To: <1409568798-2292-1-git-send-email-junmuzi@gmail.com>
On Mon, 1 Sep 2014 18:52:48 +0800
Jun Li <junmuzi@gmail.com> 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;
Hi,
k = 0 is also done in the for block below...
> + int refcount_block_entries = s->cluster_size / sizeof(uint16_t);
It's better for maintainance to count elements in an array this way:
int refcount_block_entries = s->cluster_size / sizeof(refcount_block[0]);
> + 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;
> +
> + }
> + }
> }
>
> ret = 0;
Cheers.
--
Gregory Kurz kurzgreg@fr.ibm.com
gkurz@linux.vnet.ibm.com
Software Engineer @ IBM/Meiosys http://www.ibm.com
Tel +33 (0)562 165 496
"Anarchy is about taking complete responsibility for yourself."
Alan Moore.
next prev parent reply other threads:[~2014-09-02 17:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-01 10:52 [Qemu-devel] [PATCH v2] qcow2: add update refcount table realization for update_refcount Jun Li
2014-09-01 11:11 ` Benoît Canet
2014-09-01 16:04 ` Jun Li
2014-09-02 13:38 ` Benoît Canet
2014-09-02 17:12 ` Greg Kurz [this message]
2014-09-22 1:45 ` jun muzi
2014-09-05 10:21 ` Kevin Wolf
2014-09-09 2:52 ` Jun Li
2014-09-09 8:21 ` Kevin Wolf
2014-09-09 14:04 ` Jun Li
2014-09-05 15:33 ` Stefan Hajnoczi
2014-09-13 15:53 ` Jun Li
2014-09-15 9:27 ` Stefan Hajnoczi
2014-09-05 15:34 ` Stefan Hajnoczi
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