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[PATCH 09/11] block/copy-before-write: add cbw_snapshot_read_{lock, unlo
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[PATCH 09/11] block/copy-before-write: add cbw_snapshot_read_{lock, unlock}() |
Date: |
Wed, 4 Aug 2021 16:17:48 +0300 |
Add interface which help to do fleecing read. To be used in the next
commit.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
block/copy-before-write.h | 5 ++
block/copy-before-write.c | 103 +++++++++++++++++++++++++++++++++++++-
2 files changed, 106 insertions(+), 2 deletions(-)
diff --git a/block/copy-before-write.h b/block/copy-before-write.h
index 51847e711a..a7e286620c 100644
--- a/block/copy-before-write.h
+++ b/block/copy-before-write.h
@@ -28,6 +28,7 @@
#include "block/block_int.h"
#include "block/block-copy.h"
+#include "block/reqlist.h"
BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
BlockDriverState *target,
@@ -36,4 +37,8 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
Error **errp);
void bdrv_cbw_drop(BlockDriverState *bs);
+int cbw_snapshot_read_lock(BlockDriverState *bs, int64_t offset,
+ int64_t bytes, const BlockReq **req, int64_t *pnum);
+void cbw_snapshot_read_unlock(BlockDriverState *bs, const BlockReq *req);
+
#endif /* COPY_BEFORE_WRITE_H */
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index b58a5e8b48..a96131358e 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -31,14 +31,78 @@
#include "block/block_int.h"
#include "block/qdict.h"
#include "block/block-copy.h"
+#include "block/reqlist.h"
#include "block/copy-before-write.h"
typedef struct BDRVCopyBeforeWriteState {
BlockCopyState *bcs;
BdrvChild *target;
+ CoMutex lock;
+
+ BdrvDirtyBitmap *access_bitmap;
+ BdrvDirtyBitmap *done_bitmap;
+
+ BlockReqList frozen_read_reqs;
} BDRVCopyBeforeWriteState;
+static BlockReq *add_read_req(BDRVCopyBeforeWriteState *s, uint64_t offset,
+ uint64_t bytes)
+{
+ BlockReq *req = g_new(BlockReq, 1);
+
+ reqlist_init_req(&s->frozen_read_reqs, req, offset, bytes);
+
+ return req;
+}
+
+static void drop_read_req(BDRVCopyBeforeWriteState *s, BlockReq *req)
+{
+ reqlist_remove_req(req);
+ g_free(req);
+}
+
+/*
+ * Convenient function for thous who want to do fleecing read.
+ *
+ * If requested region starts in "done" area, i.e. data is already copied to
+ * copy-before-write target node, req is set to NULL, pnum is set to available
+ * bytes to read from target. User is free to read @pnum bytes from target.
+ * Still, user is responsible for concurrent discards on target.
+ *
+ * If requests region starts in "not done" area, i.e. we have to read from
+ * source node directly, than @pnum bytes of source node are frozen and
+ * guaranteed not be rewritten until user calls cbw_snapshot_read_unlock().
+ */
+int cbw_snapshot_read_lock(BlockDriverState *bs, int64_t offset,
+ int64_t bytes, const BlockReq **req, int64_t *pnum)
+{
+ BDRVCopyBeforeWriteState *s = bs->opaque;
+ bool done;
+
+ QEMU_LOCK_GUARD(&s->lock);
+
+ if (bdrv_dirty_bitmap_next_zero(s->access_bitmap, offset, bytes) != -1) {
+ return -EACCES;
+ }
+
+ bdrv_dirty_bitmap_status(s->done_bitmap, offset, bytes, &done, pnum);
+ if (!done) {
+ *req = add_read_req(s, offset, *pnum);
+ }
+
+ return 0;
+}
+
+void cbw_snapshot_read_unlock(BlockDriverState *bs, const BlockReq *req)
+{
+ BDRVCopyBeforeWriteState *s = bs->opaque;
+
+ QEMU_LOCK_GUARD(&s->lock);
+
+ drop_read_req(s, (BlockReq *)req);
+}
+
static coroutine_fn int cbw_co_preadv(
BlockDriverState *bs, uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
@@ -50,6 +114,7 @@ static coroutine_fn int
cbw_do_copy_before_write(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, BdrvRequestFlags flags)
{
BDRVCopyBeforeWriteState *s = bs->opaque;
+ int ret;
uint64_t off, end;
int64_t cluster_size = block_copy_cluster_size(s->bcs);
@@ -60,7 +125,17 @@ static coroutine_fn int
cbw_do_copy_before_write(BlockDriverState *bs,
off = QEMU_ALIGN_DOWN(offset, cluster_size);
end = QEMU_ALIGN_UP(offset + bytes, cluster_size);
- return block_copy(s->bcs, off, end - off, true);
+ ret = block_copy(s->bcs, off, end - off, true);
+ if (ret < 0) {
+ return ret;
+ }
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ bdrv_set_dirty_bitmap(s->done_bitmap, off, end - off);
+ reqlist_wait_all(&s->frozen_read_reqs, off, end - off, &s->lock);
+ }
+
+ return 0;
}
static int coroutine_fn cbw_co_pdiscard(BlockDriverState *bs,
@@ -148,7 +223,11 @@ static int cbw_open(BlockDriverState *bs, QDict *options,
int flags,
Error **errp)
{
BDRVCopyBeforeWriteState *s = bs->opaque;
- BdrvDirtyBitmap *bitmap = NULL;
+ BdrvDirtyBitmap *bcs_bitmap, *bitmap = NULL;
+ bool ok;
+
+ qemu_co_mutex_init(&s->lock);
+ QLIST_INIT(&s->frozen_read_reqs);
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
@@ -202,6 +281,23 @@ static int cbw_open(BlockDriverState *bs, QDict *options,
int flags,
return -EINVAL;
}
+ bcs_bitmap = block_copy_dirty_bitmap(s->bcs);
+
+ /* done_bitmap starts empty */
+ s->done_bitmap =
+ bdrv_create_dirty_bitmap(bs, block_copy_cluster_size(s->bcs), NULL,
+ errp);
+ bdrv_disable_dirty_bitmap(s->done_bitmap);
+ /* access_bitmap starts equal to bcs_bitmap */
+ s->access_bitmap =
+ bdrv_create_dirty_bitmap(bs, block_copy_cluster_size(s->bcs), NULL,
+ errp);
+ bdrv_disable_dirty_bitmap(s->access_bitmap);
+ ok = bdrv_dirty_bitmap_merge_internal(s->access_bitmap, bcs_bitmap, NULL,
+ true);
+ /* Merge fails iff bitmaps has different size */
+ assert(ok);
+
return 0;
}
@@ -211,6 +307,9 @@ static void cbw_close(BlockDriverState *bs)
block_copy_state_free(s->bcs);
s->bcs = NULL;
+
+ bdrv_release_dirty_bitmap(s->access_bitmap);
+ bdrv_release_dirty_bitmap(s->done_bitmap);
}
BlockDriver bdrv_cbw_filter = {
--
2.29.2
- [PATCH RFC DRAFT 00/11] Make image fleecing more usable, Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 01/11] block/block-copy: move copy_bitmap initialization to block_copy_state_new(), Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 02/11] block/dirty-bitmap: bdrv_merge_dirty_bitmap(): add return value, Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 04/11] block/copy-before-write: add bitmap open parameter, Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 03/11] block/block-copy: block_copy_state_new(): add bitmap parameter, Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 05/11] block/block-copy: add block_copy_reset(), Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 06/11] block: intoduce reqlist, Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 07/11] block/dirty-bitmap: introduce bdrv_dirty_bitmap_status(), Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 08/11] block/reqlist: add reqlist_wait_all(), Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 09/11] block/copy-before-write: add cbw_snapshot_read_{lock, unlock}(),
Vladimir Sementsov-Ogievskiy <=
- [PATCH 10/11] block/copy-before-write: add cbw_snapshot_discard(), Vladimir Sementsov-Ogievskiy, 2021/08/04
- [PATCH 11/11] block: introduce fleecing block driver, Vladimir Sementsov-Ogievskiy, 2021/08/04