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Re: [Qemu-devel] [PATCH v3 2/3] block/backup: avoid copying less than fu
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/3] block/backup: avoid copying less than full target clusters |
Date: |
Tue, 23 Feb 2016 17:45:44 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 |
On 02/23/2016 05:27 PM, Fam Zheng wrote:
> On Tue, 02/23 19:17, John Snow wrote:
>> During incremental backups, if the target has a cluster size that is
>> larger than the backup cluster size and we are backing up to a target
>> that cannot (for whichever reason) pull clusters up from a backing image,
>> we may inadvertantly create unusable incremental backup images.
>>
>> + /* If there is no backing file on the target, we cannot rely on COW if
>> our
>> + * backup cluster size is smaller than the target cluster size. Even for
>> + * targets with a backing file, try to avoid COW if possible. */
>> + ret = bdrv_get_info(job->target, &bdi);
>> + if (ret < 0 && !target->backing) {
>> + error_setg_errno(errp, -ret,
>> + "Can't determine cluster size of target that has no backing
>> file. "
>> + "This may create an unusable destination image. Aborting.");
>
> Most error messages don't end with a period, but that's not a hard rule
> AFAICT.
Ah, but it is:
include/qapi/error.h:
* The resulting message should be a single phrase, with no newline or
* trailing punctuation.
* Please don't error_setg(&error_fatal, ...), use error_report() and
* exit(), because that's more obvious.
* Likewise, don't error_setg(&error_abort, ...), use assert().
*/
#define error_setg(errp, fmt, ...) \
The error message should be "Can't determine cluster size of target
without backing file"; everything else should be done with
error_append_hint(&errp, "Aborting, since this may create an unusable
destination image\n")
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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[Qemu-devel] [PATCH v3 3/3] iotests/124: Add cluster_size mismatch test, John Snow, 2016/02/23
[Qemu-devel] [PATCH v3 1/3] block/backup: make backup cluster size configurable, John Snow, 2016/02/23