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block-copy: move detecting fleecing scheme to block-copy
We want to simplify initialization interface of copy-before-write filter as we are going to make it public. So, let's detect fleecing scheme exactly in block-copy code, to not pass this information through extra levels. Why not just set BDRV_REQ_SERIALISING unconditionally: because we are going to implement new more efficient fleecing scheme which will not rely on backing feature. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Message-Id: <20210824083856.17408-7-vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
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parent
d003e0aece
commit
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5 changed files with 26 additions and 28 deletions
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@ -407,7 +407,6 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
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int64_t len, target_len;
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BackupBlockJob *job = NULL;
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int64_t cluster_size;
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BdrvRequestFlags write_flags;
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BlockDriverState *cbw = NULL;
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BlockCopyState *bcs = NULL;
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@ -504,26 +503,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
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goto error;
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}
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/*
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* If source is in backing chain of target assume that target is going to be
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* used for "image fleecing", i.e. it should represent a kind of snapshot of
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* source at backup-start point in time. And target is going to be read by
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* somebody (for example, used as NBD export) during backup job.
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*
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* In this case, we need to add BDRV_REQ_SERIALISING write flag to avoid
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* intersection of backup writes and third party reads from target,
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* otherwise reading from target we may occasionally read already updated by
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* guest data.
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*
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* For more information see commit f8d59dfb40bb and test
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* tests/qemu-iotests/222
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*/
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write_flags = (bdrv_chain_contains(target, bs) ? BDRV_REQ_SERIALISING : 0) |
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(compress ? BDRV_REQ_WRITE_COMPRESSED : 0),
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cbw = bdrv_cbw_append(bs, target, filter_node_name,
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cluster_size, perf,
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write_flags, &bcs, errp);
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cluster_size, perf, compress, &bcs, errp);
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if (!cbw) {
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goto error;
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}
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