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Re: [Qemu-devel] [PATCH v6 04/24] qcow2: Only return status from qcow2_g
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH v6 04/24] qcow2: Only return status from qcow2_get_refcount |
Date: |
Tue, 17 Feb 2015 11:19:52 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 10.02.2015 um 21:28 hat Max Reitz geschrieben:
> Refcounts can theoretically be of type uint64_t; in order to be able to
> represent the full range, qcow2_get_refcount() cannot use a single
> variable to represent both all refcount values and also keep some values
> reserved for errors.
>
> One solution would be to add an Error pointer parameter to
> qcow2_get_refcount(); however, no caller could (currently) pass that
> error message, so it would have to be emitted immediately and be
> passed to the next caller by returning -EIO or something similar.
> Therefore, an Error parameter does not offer any advantages here.
>
> The solution applied by this patch is simpler to use. Because no caller
> would be able to pass the error message, they would have to print it and
> free it, whereas with this patch the caller only needs to pass the
> returned integer (which is often a no-op from the code perspective,
> because that integer will be stored in a variable "ret" which will be
> returned by the fail path of many callers).
>
> Signed-off-by: Max Reitz <address@hidden>
> @@ -1646,13 +1653,14 @@ static void compare_refcounts(BlockDriverState *bs,
> BdrvCheckResult *res,
> {
> BDRVQcowState *s = bs->opaque;
> int64_t i;
> - int refcount1, refcount2, ret;
> + uint16_t refcount1, refcount2;
> + int ret;
>
> for (i = 0, *highest_cluster = 0; i < nb_clusters; i++) {
> - refcount1 = qcow2_get_refcount(bs, i);
> - if (refcount1 < 0) {
> + ret = qcow2_get_refcount(bs, i, &refcount1);
> + if (ret < 0) {
> fprintf(stderr, "Can't get refcount for cluster %" PRId64 ":
> %s\n",
> - i, strerror(-refcount1));
> + i, strerror(-ret));
> res->check_errors++;
> continue;
> }
> @@ -1682,7 +1690,7 @@ static void compare_refcounts(BlockDriverState *bs,
> BdrvCheckResult *res,
>
> if (num_fixed) {
> ret = update_refcount(bs, i << s->cluster_bits, 1,
> - refcount2 - refcount1,
> + (int)refcount2 - (int)refcount1,
> QCOW2_DISCARD_ALWAYS);
> if (ret >= 0) {
> (*num_fixed)++;
Wouldn't both refcounts be promoted to int anyway, even without a cast?
But then, being explicit probably can't hurt either.
Kevin
- [Qemu-devel] [PATCH v6 00/24] qcow2: Support refcount orders != 4, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 01/24] qcow2: Add two new fields to BDRVQcowState, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 03/24] qcow2: Do not return new value after refcount update, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 02/24] qcow2: Add refcount_bits to format-specific info, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 04/24] qcow2: Only return status from qcow2_get_refcount, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 05/24] qcow2: Use unsigned addend for update_refcount(), Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 06/24] qcow2: Use 64 bits for refcount values, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 10/24] qcow2: Open images with refcount order != 4, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 08/24] qcow2: Helper function for refcount modification, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 12/24] qcow2: Use symbolic macros in qcow2_amend_options, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 07/24] qcow2: Helper for refcount array reallocation, Max Reitz, 2015/02/10