From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Hanna Reitz <hreitz@redhat.com>, qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, kwolf@redhat.com, nsoffer@redhat.com,
eblake@redhat.com, jsnow@redhat.com, den@openvz.org,
nikita.lapshin@virtuozzo.com
Subject: Re: [PATCH v2 2/4] qemu-img: make --block-size optional for compare --stat
Date: Thu, 28 Oct 2021 13:04:24 +0300 [thread overview]
Message-ID: <d1f58c9e-f578-7017-282a-26deda1644c4@virtuozzo.com> (raw)
In-Reply-To: <3afe188c-e6de-e956-b068-af6ae1f988da@redhat.com>
26.10.2021 11:07, Hanna Reitz wrote:
> On 21.10.21 12:12, Vladimir Sementsov-Ogievskiy wrote:
>> Let's detect block-size automatically if not specified by user:
>>
>> If both files define cluster-size, use minimum to be more precise.
>> If both files don't specify cluster-size, use default of 64K
>> If only one file specify cluster-size, just use it.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>> docs/tools/qemu-img.rst | 7 +++-
>> qemu-img.c | 71 ++++++++++++++++++++++++++++++++++++-----
>> qemu-img-cmds.hx | 4 +--
>> 3 files changed, 71 insertions(+), 11 deletions(-)
>
> Looks good, just grammar nits and a request for an assertion below.
>
>> diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
>> index 21164253d4..4b382ca2b0 100644
>> --- a/docs/tools/qemu-img.rst
>> +++ b/docs/tools/qemu-img.rst
>> @@ -170,6 +170,11 @@ Parameters to compare subcommand:
>> Block size for comparing with ``--stat``. This doesn't guarantee exact
>> size of comparing chunks, but that guarantee that data chunks being
>> compared will never cross aligned block-size boundary.
>> + When unspecified the following logic is used:
>> +
>> + - If both files define cluster-size, use minimum to be more precise.
>> + - If both files don't specify cluster-size, use default of 64K
>> + - If only one file specify cluster-size, just use it.
>
> s/specify/specifies/; and perhaps s/it/that/
>
> [...]
>
>> diff --git a/qemu-img.c b/qemu-img.c
>> index 79a0589167..61e7f470bb 100644
>> --- a/qemu-img.c
>> +++ b/qemu-img.c
>> @@ -1407,6 +1407,61 @@ static void cmp_stat_print(ImgCmpStat *stat, int64_t total_bytes)
>> }
>> }
>> +/* Get default value for qemu-img compare --block-size option. */
>> +static int img_compare_block_size(BlockDriverState *bs1,
>> + BlockDriverState *bs2,
>> + bool quiet)
>> +{
>> + const int default_block_size = 64 * 1024; /* 64K */
>> +
>> + int ret;
>> + BlockDriverInfo bdi;
>> + int cluster_size1, cluster_size2, block_size;
>> + const char *note = "Note: to alter it, set --block-size option.";
>> + const char *fname1 = bs1->filename;
>> + const char *fname2 = bs2->filename;
>> +
>> + ret = bdrv_get_info(bs1, &bdi);
>> + if (ret < 0 && ret != -ENOTSUP) {
>> + error_report("Failed to get info of %s: %s", fname1, strerror(-ret));
>> + return ret;
>> + }
>> + cluster_size1 = ret < 0 ? 0 : bdi.cluster_size;
>> +
>> + ret = bdrv_get_info(bs2, &bdi);
>> + if (ret < 0 && ret != -ENOTSUP) {
>> + error_report("Failed to get info of %s: %s", fname2, strerror(-ret));
>> + return ret;
>> + }
>> + cluster_size2 = ret < 0 ? 0 : bdi.cluster_size;
>> +
>
> I’d feel better with an `assert(cluster_size1 >= 0 && cluster_size2 >= 0);` here.
Hmm.. But it seems obvious: bdi.cluster_size should not be <0 on success of bdrv_get_info.
>
>> + if (cluster_size1 > 0 && cluster_size2 > 0) {
>> + if (cluster_size1 == cluster_size2) {
>> + block_size = cluster_size1;
>> + } else {
>> + block_size = MIN(cluster_size1, cluster_size2);
>> + qprintf(quiet, "%s and %s has different cluster sizes: %d and %d "
>
> s/has/have/
>
>> + "correspondingly. Use minimum as block-size for "
>
> s/correspondingly/respectively/; s/Use/Using/ (“Use” sounds like an imperative)
>
>> + "accuracy: %d. %s\n",
>> + fname1, fname2, cluster_size1,
>> + cluster_size2, block_size, note);
>> + }
>> + } else if (cluster_size1 == 0 && cluster_size2 == 0) {
>> + block_size = default_block_size;
>> + qprintf(quiet, "Neither of %s and %s has explicit cluster size. Use "
>
> s/has/have an/; s/Use/Using/
>
>> + "default of %d bytes. %s\n", fname1, fname2, block_size, note);
>> + } else {
>> + block_size = MAX(cluster_size1, cluster_size2);
>> + qprintf(quiet, "%s has explicit cluster size of %d and %s "
>
> s/has/has an/
>
>> + "doesn't have one. Use %d as block-size. %s\n",
>
> s/Use/Using/
>
> Hanna
>
>> + cluster_size1 ? fname1 : fname2, block_size,
>> + cluster_size1 ? fname2 : fname1,
>> + block_size, note);
>> + }
>> +
>> + return block_size;
>> +}
>> +
>> /*
>> * Compares two images. Exit codes:
>> *
>
--
Best regards,
Vladimir
next prev parent reply other threads:[~2021-10-28 10:06 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-21 10:12 [PATCH v2 0/4] qemu-img compare --stat Vladimir Sementsov-Ogievskiy
2021-10-21 10:12 ` [PATCH v2 1/4] qemu-img: implement " Vladimir Sementsov-Ogievskiy
2021-10-25 16:40 ` Hanna Reitz
2021-10-26 7:53 ` Vladimir Sementsov-Ogievskiy
2021-10-26 8:47 ` Hanna Reitz
2021-10-26 9:18 ` Vladimir Sementsov-Ogievskiy
2021-10-27 8:35 ` Hanna Reitz
2021-10-21 10:12 ` [PATCH v2 2/4] qemu-img: make --block-size optional for " Vladimir Sementsov-Ogievskiy
2021-10-26 8:07 ` Hanna Reitz
2021-10-28 10:04 ` Vladimir Sementsov-Ogievskiy [this message]
2021-10-21 10:12 ` [PATCH v2 3/4] qemu-img: add --shallow option for qemu-img compare Vladimir Sementsov-Ogievskiy
2021-10-26 8:11 ` Hanna Reitz
2021-10-21 10:12 ` [PATCH v2 4/4] iotests: add qemu-img-compare-stat test Vladimir Sementsov-Ogievskiy
2021-10-26 8:26 ` Hanna Reitz
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