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[Qemu-devel] [RFC PATCH v2 18/23] qcow2: Delay the COW
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [RFC PATCH v2 18/23] qcow2: Delay the COW |
Date: |
Wed, 13 Feb 2013 14:22:08 +0100 |
Signed-off-by: Kevin Wolf <address@hidden>
---
block/qcow2-cluster.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
block/qcow2.c | 28 +++++++++++++++++++++++++---
block/qcow2.h | 14 ++++++++++++++
3 files changed, 86 insertions(+), 3 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index be75c17..33e595a 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -791,6 +791,52 @@ out:
return i;
}
+struct KickL2Meta {
+ QEMUBH *bh;
+ QCowL2Meta *m;
+};
+
+static void kick_l2meta_bh(void *opaque)
+{
+ struct KickL2Meta *k = opaque;
+ QCowL2Meta *m = k->m;
+
+ m->kick_l2meta = NULL;
+ qemu_bh_delete(k->bh);
+ g_free(k);
+
+ if (m->sleeping) {
+ qemu_coroutine_enter(m->co, NULL);
+ }
+}
+
+static void kick_l2meta(QCowL2Meta *m)
+{
+ struct KickL2Meta *k;
+
+ if (m->kick_l2meta) {
+ return;
+ }
+
+ k = g_malloc(sizeof(*k));
+ k->bh = qemu_bh_new(kick_l2meta_bh, k);
+ k->m = m;
+
+ m->kick_l2meta = k;
+
+ qemu_bh_schedule(k->bh);
+}
+
+void qcow2_delete_kick_l2meta_bh(void *opaque)
+{
+ if (opaque) {
+ struct KickL2Meta *k = opaque;
+
+ qemu_bh_delete(k->bh);
+ g_free(k);
+ }
+}
+
/*
* Check if there already is an AIO write request in flight which allocates
* the same cluster. In this case we need to wait until the previous
@@ -833,6 +879,7 @@ static int handle_dependencies(BlockDriverState *bs,
uint64_t guest_offset,
/* Wait for the dependency to complete. We need to recheck
* the free/allocated clusters when we continue. */
qemu_co_mutex_unlock(&s->lock);
+ kick_l2meta(old_alloc);
qemu_co_queue_wait(&old_alloc->dependent_requests);
qemu_co_mutex_lock(&s->lock);
return -EAGAIN;
diff --git a/block/qcow2.c b/block/qcow2.c
index 3f169b8..57552aa 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -767,6 +767,13 @@ static void coroutine_fn process_l2meta(void *opaque)
int ret;
assert(s->l2meta_flush.reader > 0);
+
+ if (!s->in_l2meta_flush) {
+ m->sleeping = true;
+ co_sleep_ns(rt_clock, 1000000);
+ m->sleeping = false;
+ }
+
qemu_co_mutex_lock(&s->lock);
ret = qcow2_alloc_cluster_link_l2(bs, m);
@@ -784,6 +791,7 @@ static void coroutine_fn process_l2meta(void *opaque)
/* Meanwhile some new dependencies could have accumulated */
qemu_co_queue_restart_all(&m->dependent_requests);
+ qcow2_delete_kick_l2meta_bh(m->kick_l2meta);
g_free(m);
qemu_co_rwlock_unlock(&s->l2meta_flush);
@@ -792,6 +800,18 @@ static void coroutine_fn process_l2meta(void *opaque)
static bool qcow2_drain(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
+ QCowL2Meta *m;
+
+ s->in_l2meta_flush = true;
+again:
+ QLIST_FOREACH(m, &s->cluster_allocs, next_in_flight) {
+ if (m->sleeping) {
+ qemu_coroutine_enter(m->co, NULL);
+ /* next_in_flight link could have become invalid */
+ goto again;
+ }
+ }
+ s->in_l2meta_flush = false;
return !QLIST_EMPTY(&s->cluster_allocs);
}
@@ -800,6 +820,9 @@ static inline coroutine_fn void
stop_l2meta(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
+ /* Kick the requests once if they are sleepeing and then just wait until
+ * they complete and we get the lock */
+ qcow2_drain(bs);
qemu_co_rwlock_wrlock(&s->l2meta_flush);
}
@@ -893,7 +916,6 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState
*bs,
qemu_co_mutex_unlock(&s->lock);
while (l2meta != NULL) {
- Coroutine *co;
QCowL2Meta *next;
ProcessL2Meta p = {
@@ -913,8 +935,8 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState
*bs,
/* l2meta might already be freed after the coroutine has run */
next = l2meta->next;
- co = qemu_coroutine_create(process_l2meta);
- qemu_coroutine_enter(co, &p);
+ l2meta->co = qemu_coroutine_create(process_l2meta);
+ qemu_coroutine_enter(l2meta->co, &p);
l2meta = next;
}
diff --git a/block/qcow2.h b/block/qcow2.h
index 46ed112..1d7cdab 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -169,6 +169,7 @@ typedef struct BDRVQcowState {
* Writers: Anyone who requires l2meta to be flushed
*/
CoRwlock l2meta_flush;
+ bool in_l2meta_flush;
uint32_t crypt_method; /* current crypt method, 0 if no key yet */
uint32_t crypt_method_header;
@@ -245,6 +246,15 @@ typedef struct QCowL2Meta
bool is_written;
/**
+ * true if the request is sleeping in the COW delay and the coroutine may
+ * be reentered in order to cancel the timer.
+ */
+ bool sleeping;
+
+ /** Coroutine that handles delayed COW and updates L2 entry */
+ Coroutine *co;
+
+ /**
* Requests that overlap with this allocation and wait to be restarted
* when the allocating request has completed.
*/
@@ -265,6 +275,8 @@ typedef struct QCowL2Meta
/** Pointer to next L2Meta of the same write request */
struct QCowL2Meta *next;
+ void *kick_l2meta;
+
QLIST_ENTRY(QCowL2Meta) next_in_flight;
} QCowL2Meta;
@@ -404,6 +416,8 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t
offset,
int nb_sectors);
int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors);
+void qcow2_delete_kick_l2meta_bh(void *opaque);
+
/* qcow2-snapshot.c functions */
int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id);
--
1.7.6.5
- [Qemu-devel] [RFC PATCH v2 06/23] qcow2: handle_alloc(): Get rid of nb_clusters parameter, (continued)
[Qemu-devel] [RFC PATCH v2 16/23] qcow2: Reading from areas not in L2 tables yet, Kevin Wolf, 2013/02/13
[Qemu-devel] [RFC PATCH v2 18/23] qcow2: Delay the COW,
Kevin Wolf <=
[Qemu-devel] [RFC PATCH v2 19/23] qcow2: Add error handling to the l2meta coroutine, Kevin Wolf, 2013/02/13
[Qemu-devel] [RFC PATCH v2 14/23] qcow2: Use byte granularity in qcow2_alloc_cluster_offset(), Kevin Wolf, 2013/02/13
[Qemu-devel] [RFC PATCH v2 17/23] qcow2: Move COW and L2 update into own coroutine, Kevin Wolf, 2013/02/13