On 30.07.19 20:40, John Snow wrote:
>
>
> On 7/30/19 12:32 PM, Vladimir Sementsov-Ogievskiy wrote:
>> We have detect_zeroes option, so at least for blockdev-backup user
>> should define it if zero-detection is needed. For drive-backup leave
>> detection enabled by default but do it through existing option instead
>> of open-coding.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
>> ---
>> block/backup.c | 15 ++++++---------
>> blockdev.c | 8 ++++----
>> 2 files changed, 10 insertions(+), 13 deletions(-)
>>
>> diff --git a/block/backup.c b/block/backup.c
>> index 715e1d3be8..f4aaf08df3 100644
>> --- a/block/backup.c
>> +++ b/block/backup.c
>> @@ -110,7 +110,10 @@ static int coroutine_fn
>> backup_cow_with_bounce_buffer(BackupBlockJob *job,
>> BlockBackend *blk = job->common.blk;
>> int nbytes;
>> int read_flags = is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0;
>> - int write_flags = job->serialize_target_writes ? BDRV_REQ_SERIALISING :
>> 0;
>> + int write_flags =
>> + (job->serialize_target_writes ? BDRV_REQ_SERIALISING : 0) |
>> + (job->compress ? BDRV_REQ_WRITE_COMPRESSED : 0);
>> +
>>
>> assert(QEMU_IS_ALIGNED(start, job->cluster_size));
>> hbitmap_reset(job->copy_bitmap, start, job->cluster_size);
>> @@ -128,14 +131,8 @@ static int coroutine_fn
>> backup_cow_with_bounce_buffer(BackupBlockJob *job,
>> goto fail;
>> }
>>
>> - if (buffer_is_zero(*bounce_buffer, nbytes)) {
>> - ret = blk_co_pwrite_zeroes(job->target, start,
>> - nbytes, write_flags |
>> BDRV_REQ_MAY_UNMAP);
>> - } else {
>> - ret = blk_co_pwrite(job->target, start,
>> - nbytes, *bounce_buffer, write_flags |
>> - (job->compress ? BDRV_REQ_WRITE_COMPRESSED :
>> 0));
>> - }
>> + ret = blk_co_pwrite(job->target, start, nbytes, *bounce_buffer,
>> + write_flags);
>> if (ret < 0) {
>> trace_backup_do_cow_write_fail(job, start, ret);
>> if (error_is_read) {
>> diff --git a/blockdev.c b/blockdev.c
>> index 4d141e9a1f..a94d754504 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -3434,7 +3434,7 @@ static BlockJob *do_drive_backup(DriveBackup *backup,
>> JobTxn *txn,
>> BlockJob *job = NULL;
>> BdrvDirtyBitmap *bmap = NULL;
>> AioContext *aio_context;
>> - QDict *options = NULL;
>> + QDict *options;
>> Error *local_err = NULL;
>> int flags, job_flags = JOB_DEFAULT;
>> int64_t size;
>> @@ -3529,10 +3529,10 @@ static BlockJob *do_drive_backup(DriveBackup
>> *backup, JobTxn *txn,
>> goto out;
>> }
>>
>> + options = qdict_new();
>> + qdict_put_str(options, "discard", "unmap");
>> + qdict_put_str(options, "detect-zeroes", "unmap");
>> if (backup->format) {
>> - if (!options) {
>> - options = qdict_new();
>> - }
>> qdict_put_str(options, "driver", backup->format);
>> }
>>
>>
>
> I'm less sure of this one personally. Is it right to always try to set
> unmap on the target?
>
> I like the idea of removing special cases and handling things more
> centrally though, but I'll want Max (or Kevin) to take a peek.I don’t quite know why, because this is just a block job specific question and doesn’t have much to do with the rest of the block layer, but OK. :-) drive-backup always set BDRV_REQ_MAY_UNMAP, as you can see. Maybe that didn’t do anything because the target wasn’t opened with discard=unmap. But to me, it’s clear that the intention was to indeed unmap the areas in the target (it isn’t like the user had a choice of opening the target with discard=unmap or not). Max
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