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[Qemu-devel] [PATCH v22 03/10] Backup: export interfaces for extra seria
From: |
Wang WeiWei |
Subject: |
[Qemu-devel] [PATCH v22 03/10] Backup: export interfaces for extra serialization |
Date: |
Fri, 22 Jul 2016 18:16:00 +0800 |
From: Changlong Xie <address@hidden>
Normal backup(sync='none') workflow:
step 1. NBD peformance I/O write from client to server
qcow2_co_writev
bdrv_co_writev
...
bdrv_aligned_pwritev
notifier_with_return_list_notify -> backup_do_cow
bdrv_driver_pwritev // write new contents
step 2. drive-backup sync=none
backup_do_cow
{
wait_for_overlapping_requests
cow_request_begin
for(; start < end; start++) {
bdrv_co_readv_no_serialising //read old contents from Secondary disk
bdrv_co_writev // write old contents to hidden-disk
}
cow_request_end
}
step 3. Then roll back to "step 1" to write new contents to Secondary disk.
And for replication, we must make sure that we only read the old contents from
Secondary disk in order to keep contents consistent.
1) Replication workflow of Secondary
virtio-blk
^
-------> 1 NBD |
|| server 3 replication
|| ^ ^
|| | backing backing |
|| Secondary disk 6<-------- hidden-disk 5 <-------- active-disk 4
|| | ^
|| '-------------------------'
|| drive-backup sync=none 2
Hence, we need these interfaces to implement coarse-grained serialization
between
COW of Secondary disk and the read operation of replication.
Example codes about how to use them:
*#include "block/block_backup.h"
static coroutine_fn int xxx_co_readv()
{
CowRequest req;
BlockJob *job = secondary_disk->bs->job;
if (job) {
backup_wait_for_overlapping_requests(job, start, end);
backup_cow_request_begin(&req, job, start, end);
ret = bdrv_co_readv();
backup_cow_request_end(&req);
goto out;
}
ret = bdrv_co_readv();
out:
return ret;
}
Signed-off-by: Changlong Xie <address@hidden>
Signed-off-by: Wen Congyang <address@hidden>
Signed-off-by: Wang WeiWei <address@hidden>
---
block/backup.c | 41 ++++++++++++++++++++++++++++++++++-------
include/block/block_backup.h | 14 ++++++++++++++
2 files changed, 48 insertions(+), 7 deletions(-)
diff --git a/block/backup.c b/block/backup.c
index 3bce416..919b63a 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -28,13 +28,6 @@
#define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16)
#define SLICE_TIME 100000000ULL /* ns */
-typedef struct CowRequest {
- int64_t start;
- int64_t end;
- QLIST_ENTRY(CowRequest) list;
- CoQueue wait_queue; /* coroutines blocked on this request */
-} CowRequest;
-
typedef struct BackupBlockJob {
BlockJob common;
BlockBackend *target;
@@ -271,6 +264,40 @@ void backup_do_checkpoint(BlockJob *job, Error **errp)
bitmap_zero(backup_job->done_bitmap, len);
}
+void backup_wait_for_overlapping_requests(BlockJob *job, int64_t sector_num,
+ int nb_sectors)
+{
+ BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common);
+ int64_t sectors_per_cluster = cluster_size_sectors(backup_job);
+ int64_t start, end;
+
+ assert(job->driver->job_type == BLOCK_JOB_TYPE_BACKUP);
+
+ start = sector_num / sectors_per_cluster;
+ end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster);
+ wait_for_overlapping_requests(backup_job, start, end);
+}
+
+void backup_cow_request_begin(CowRequest *req, BlockJob *job,
+ int64_t sector_num,
+ int nb_sectors)
+{
+ BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common);
+ int64_t sectors_per_cluster = cluster_size_sectors(backup_job);
+ int64_t start, end;
+
+ assert(job->driver->job_type == BLOCK_JOB_TYPE_BACKUP);
+
+ start = sector_num / sectors_per_cluster;
+ end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster);
+ cow_request_begin(req, backup_job, start, end);
+}
+
+void backup_cow_request_end(CowRequest *req)
+{
+ cow_request_end(req);
+}
+
static const BlockJobDriver backup_job_driver = {
.instance_size = sizeof(BackupBlockJob),
.job_type = BLOCK_JOB_TYPE_BACKUP,
diff --git a/include/block/block_backup.h b/include/block/block_backup.h
index 3753bcb..e0e7ce6 100644
--- a/include/block/block_backup.h
+++ b/include/block/block_backup.h
@@ -1,3 +1,17 @@
#include "block/block_int.h"
+typedef struct CowRequest {
+ int64_t start;
+ int64_t end;
+ QLIST_ENTRY(CowRequest) list;
+ CoQueue wait_queue; /* coroutines blocked on this request */
+} CowRequest;
+
+void backup_wait_for_overlapping_requests(BlockJob *job, int64_t sector_num,
+ int nb_sectors);
+void backup_cow_request_begin(CowRequest *req, BlockJob *job,
+ int64_t sector_num,
+ int nb_sectors);
+void backup_cow_request_end(CowRequest *req);
+
void backup_do_checkpoint(BlockJob *job, Error **errp);
--
1.9.3
- [Qemu-devel] [PATCH v22 00/10] Block replication for continuous checkpoints, Wang WeiWei, 2016/07/22
- [Qemu-devel] [PATCH v22 01/10] unblock backup operations in backing file, Wang WeiWei, 2016/07/22
- [Qemu-devel] [PATCH v22 02/10] Backup: clear all bitmap when doing block checkpoint, Wang WeiWei, 2016/07/22
- [Qemu-devel] [PATCH v22 03/10] Backup: export interfaces for extra serialization,
Wang WeiWei <=
- [Qemu-devel] [PATCH v22 06/10] auto complete active commit, Wang WeiWei, 2016/07/22
- [Qemu-devel] [PATCH v22 04/10] Link backup into block core, Wang WeiWei, 2016/07/22
- [Qemu-devel] [PATCH v22 05/10] docs: block replication's description, Wang WeiWei, 2016/07/22
- [Qemu-devel] [PATCH v22 10/10] support replication driver in blockdev-add, Wang WeiWei, 2016/07/22
- [Qemu-devel] [PATCH v22 07/10] Introduce new APIs to do replication operation, Wang WeiWei, 2016/07/22