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[Qemu-devel] [RFC PATCH 02/16] qcow2: Introduce Qcow2COWRegion
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [RFC PATCH 02/16] qcow2: Introduce Qcow2COWRegion |
Date: |
Tue, 18 Sep 2012 13:40:28 +0200 |
This makes it easier to address the areas for which a COW must be
performed. As a nice side effect, the COW code in
qcow2_alloc_cluster_link_l2 becomes really trivial.
Signed-off-by: Kevin Wolf <address@hidden>
---
block/qcow2-cluster.c | 85 +++++++++++++++++++++++++++++++------------------
block/qcow2.h | 29 +++++++++++++---
2 files changed, 77 insertions(+), 37 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index d17a37c..94b7f13 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -615,13 +615,41 @@ uint64_t
qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
return cluster_offset;
}
+static int perform_cow(BlockDriverState *bs, QCowL2Meta *m, Qcow2COWRegion *r)
+{
+ BDRVQcowState *s = bs->opaque;
+ int ret;
+
+ if (r->nb_sectors == 0) {
+ return 0;
+ }
+
+ qemu_co_mutex_unlock(&s->lock);
+ ret = copy_sectors(bs, m->offset / BDRV_SECTOR_SIZE, m->alloc_offset,
+ r->offset / BDRV_SECTOR_SIZE,
+ r->offset / BDRV_SECTOR_SIZE + r->nb_sectors);
+ qemu_co_mutex_lock(&s->lock);
+
+ if (ret < 0) {
+ return ret;
+ }
+
+ /*
+ * Before we update the L2 table to actually point to the new cluster, we
+ * need to be sure that the refcounts have been increased and COW was
+ * handled.
+ */
+ qcow2_cache_depends_on_flush(s->l2_table_cache);
+
+ return 0;
+}
+
int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
{
BDRVQcowState *s = bs->opaque;
int i, j = 0, l2_index, ret;
- uint64_t *old_cluster, start_sect, *l2_table;
+ uint64_t *old_cluster, *l2_table;
uint64_t cluster_offset = m->alloc_offset;
- bool cow = false;
trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters);
@@ -631,36 +659,17 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs,
QCowL2Meta *m)
old_cluster = g_malloc(m->nb_clusters * sizeof(uint64_t));
/* copy content of unmodified sectors */
- start_sect = m->offset >> 9;
- if (m->n_start) {
- cow = true;
- qemu_co_mutex_unlock(&s->lock);
- ret = copy_sectors(bs, start_sect, cluster_offset, 0, m->n_start);
- qemu_co_mutex_lock(&s->lock);
- if (ret < 0)
- goto err;
+ ret = perform_cow(bs, m, &m->cow_start);
+ if (ret < 0) {
+ goto err;
}
- if (m->nb_available & (s->cluster_sectors - 1)) {
- cow = true;
- qemu_co_mutex_unlock(&s->lock);
- ret = copy_sectors(bs, start_sect, cluster_offset, m->nb_available,
- align_offset(m->nb_available, s->cluster_sectors));
- qemu_co_mutex_lock(&s->lock);
- if (ret < 0)
- goto err;
+ ret = perform_cow(bs, m, &m->cow_end);
+ if (ret < 0) {
+ goto err;
}
- /*
- * Update L2 table.
- *
- * Before we update the L2 table to actually point to the new cluster, we
- * need to be sure that the refcounts have been increased and COW was
- * handled.
- */
- if (cow) {
- qcow2_cache_depends_on_flush(s->l2_table_cache);
- }
+ /* Update L2 table. */
if (qcow2_need_accurate_refcounts(s)) {
qcow2_cache_set_dependency(bs, s->l2_table_cache,
@@ -957,19 +966,33 @@ again:
*
* avail_sectors: Number of sectors from the start of the first
* newly allocated to the end of the last newly allocated cluster.
+ *
+ * nb_sectors: The number of sectors from the start of the first
+ * newly allocated cluster to the end of the aread that the write
+ * request actually writes to (excluding COW at the end)
*/
int requested_sectors = n_end - keep_clusters * s->cluster_sectors;
int avail_sectors = nb_clusters
<< (s->cluster_bits - BDRV_SECTOR_BITS);
+ int alloc_n_start = keep_clusters == 0 ? n_start : 0;
+ int nb_sectors = MIN(requested_sectors, avail_sectors);
*m = (QCowL2Meta) {
.cluster_offset = keep_clusters == 0 ?
alloc_cluster_offset : cluster_offset,
.alloc_offset = alloc_cluster_offset,
.offset = alloc_offset & ~(s->cluster_size - 1),
- .n_start = keep_clusters == 0 ? n_start : 0,
.nb_clusters = nb_clusters,
- .nb_available = MIN(requested_sectors, avail_sectors),
+ .nb_available = nb_sectors,
+
+ .cow_start = {
+ .offset = 0,
+ .nb_sectors = alloc_n_start,
+ },
+ .cow_end = {
+ .offset = nb_sectors * BDRV_SECTOR_SIZE,
+ .nb_sectors = avail_sectors - nb_sectors,
+ },
};
qemu_co_queue_init(&m->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, m, next_in_flight);
diff --git a/block/qcow2.h b/block/qcow2.h
index 2a406a7..1106b33 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -196,6 +196,17 @@ typedef struct QCowCreateState {
struct QCowAIOCB;
+typedef struct Qcow2COWRegion {
+ /**
+ * Offset of the COW region in bytes from the start of the first cluster
+ * touched by the request.
+ */
+ uint64_t offset;
+
+ /** Number of sectors to copy */
+ int nb_sectors;
+} Qcow2COWRegion;
+
/* XXX This could be private for qcow2-cluster.c */
typedef struct QCowL2Meta
{
@@ -209,12 +220,6 @@ typedef struct QCowL2Meta
uint64_t alloc_offset;
/**
- * Number of sectors between the start of the first allocated cluster and
- * the area that the guest actually writes to.
- */
- int n_start;
-
- /**
* Number of sectors from the start of the first allocated cluster to
* the end of the (possibly shortened) request
*/
@@ -229,6 +234,18 @@ typedef struct QCowL2Meta
*/
CoQueue dependent_requests;
+ /**
+ * The COW Region between the start of the first allocated cluster and the
+ * area the guest actually writes to.
+ */
+ Qcow2COWRegion cow_start;
+
+ /**
+ * The COW Region between the area the guest actually writes to and the
+ * end of the last allocated cluster.
+ */
+ Qcow2COWRegion cow_end;
+
QLIST_ENTRY(QCowL2Meta) next_in_flight;
} QCowL2Meta;
--
1.7.6.5
- [Qemu-devel] [RFC PATCH 00/16] qcow2: Delayed COW, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 03/16] qcow2: Allocate l2meta dynamically, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 08/16] qcow2: Reading from areas not in L2 tables yet, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 16/16] [BROKEN] qcow2: Overwrite COW and allocate new cluster at the same time, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 02/16] qcow2: Introduce Qcow2COWRegion,
Kevin Wolf <=
- [Qemu-devel] [RFC PATCH 01/16] qcow2: Round QCowL2Meta.offset down to cluster boundary, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 04/16] qcow2: Drop l2meta.cluster_offset, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 07/16] qcow2: Factor out handle_dependencies(), Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 06/16] qcow2: Enable dirty flag in qcow2_alloc_cluster_link_l2, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 05/16] qcow2: Allocate l2meta only for cluster allocations, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 12/16] qcow2: Handle dependencies earlier, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 14/16] qcow2: Execute run_dependent_requests() without lock, Kevin Wolf, 2012/09/18
- [Qemu-devel] [RFC PATCH 09/16] qcow2: Move COW and L2 update into own coroutine, Kevin Wolf, 2012/09/18