I also suggest this as a prepartion (and partly substitution) for
"[PATCH v2 0/8] Block layer thread-safety, continued"
include/block/block_int.h | 12 -----
include/block/write-threshold.h | 24 ---------
block.c | 1 -
block/io.c | 21 +++++---
block/write-threshold.c | 87 ++-----------------------------
tests/unit/test-write-threshold.c | 38 ++++++++++++++
6 files changed, 54 insertions(+), 129 deletions(-)
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 88e4111939..50af58af75 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -957,12 +957,8 @@ struct BlockDriverState {
*/
int64_t total_sectors;
- /* Callback before write request is processed */
- NotifierWithReturnList before_write_notifiers;
-
/* threshold limit for writes, in bytes. "High water mark". */
uint64_t write_threshold_offset;
- NotifierWithReturn write_threshold_notifier;
/* Writing to the list requires the BQL _and_ the dirty_bitmap_mutex.
* Reading from the list can be done with either the BQL or the
@@ -1087,14 +1083,6 @@ void bdrv_parse_filename_strip_prefix(const char
*filename, const char *prefix,
bool bdrv_backing_overridden(BlockDriverState *bs);
-/**
- * bdrv_add_before_write_notifier:
- *
- * Register a callback that is invoked before write requests are processed but
- * after any throttling or waiting for overlapping requests.
- */
-void bdrv_add_before_write_notifier(BlockDriverState *bs,
- NotifierWithReturn *notifier);
/**
* bdrv_add_aio_context_notifier:
diff --git a/include/block/write-threshold.h b/include/block/write-threshold.h
index c646f267a4..23e1bfc123 100644
--- a/include/block/write-threshold.h
+++ b/include/block/write-threshold.h
@@ -35,28 +35,4 @@ void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t
threshold_bytes);
*/
uint64_t bdrv_write_threshold_get(const BlockDriverState *bs);
-/*
- * bdrv_write_threshold_is_set
- *
- * Tell if a write threshold is set for a given BDS.
- */
-bool bdrv_write_threshold_is_set(const BlockDriverState *bs);
-
-/*
- * bdrv_write_threshold_exceeded
- *
- * Return the extent of a write request that exceeded the threshold,
- * or zero if the request is below the threshold.
- * Return zero also if the threshold was not set.
- *
- * NOTE: here we assume the following holds for each request this code
- * deals with:
- *
- * assert((req->offset + req->bytes) <= UINT64_MAX)
- *
- * Please not there is *not* an actual C assert().
- */
-uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs,
- const BdrvTrackedRequest *req);
-
#endif
diff --git a/block.c b/block.c
index c5b887cec1..001453105e 100644
--- a/block.c
+++ b/block.c
@@ -381,7 +381,6 @@ BlockDriverState *bdrv_new(void)
for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
QLIST_INIT(&bs->op_blockers[i]);
}
- notifier_with_return_list_init(&bs->before_write_notifiers);
qemu_co_mutex_init(&bs->reqs_lock);
qemu_mutex_init(&bs->dirty_bitmap_mutex);
bs->refcnt = 1;
diff --git a/block/io.c b/block/io.c
index ca2dca3007..e0aa775952 100644
--- a/block/io.c
+++ b/block/io.c
@@ -36,6 +36,8 @@
#include "qemu/main-loop.h"
#include "sysemu/replay.h"
+#include "qapi/qapi-events-block-core.h"
+
/* Maximum bounce buffer for copy-on-read and write zeroes, in bytes */
#define MAX_BOUNCE_BUFFER (32768 << BDRV_SECTOR_BITS)
@@ -1974,6 +1976,8 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, int64_t bytes,
child->perm & BLK_PERM_RESIZE);
switch (req->type) {
+ uint64_t write_threshold;
+
case BDRV_TRACKED_WRITE:
case BDRV_TRACKED_DISCARD:
if (flags & BDRV_REQ_WRITE_UNCHANGED) {
@@ -1981,8 +1985,15 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t
offset, int64_t bytes,
} else {
assert(child->perm & BLK_PERM_WRITE);
}
- return notifier_with_return_list_notify(&bs->before_write_notifiers,
- req);
+ write_threshold = qatomic_read(&bs->write_threshold_offset);
+ if (write_threshold > 0 && offset + bytes > write_threshold) {
+ qapi_event_send_block_write_threshold(
+ bs->node_name,
+ offset + bytes - write_threshold,
+ write_threshold);
+ qatomic_set(&bs->write_threshold_offset, 0);
+ }
+ return 0;
case BDRV_TRACKED_TRUNCATE:
assert(child->perm & BLK_PERM_RESIZE);
return 0;
@@ -3137,12 +3148,6 @@ bool bdrv_qiov_is_aligned(BlockDriverState *bs,
QEMUIOVector *qiov)
return true;
}
-void bdrv_add_before_write_notifier(BlockDriverState *bs,
- NotifierWithReturn *notifier)
-{
- notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
-}
-
void bdrv_io_plug(BlockDriverState *bs)
{
BdrvChild *child;
diff --git a/block/write-threshold.c b/block/write-threshold.c
index 85b78dc2a9..9bf4287c6e 100644
--- a/block/write-threshold.c
+++ b/block/write-threshold.c
@@ -21,104 +21,23 @@
uint64_t bdrv_write_threshold_get(const BlockDriverState *bs)
{
- return bs->write_threshold_offset;
-}
-
-bool bdrv_write_threshold_is_set(const BlockDriverState *bs)
-{
- return bs->write_threshold_offset > 0;
-}
-
-static void write_threshold_disable(BlockDriverState *bs)
-{
- if (bdrv_write_threshold_is_set(bs)) {
- notifier_with_return_remove(&bs->write_threshold_notifier);
- bs->write_threshold_offset = 0;
- }
-}
-
-uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs,
- const BdrvTrackedRequest *req)
-{
- if (bdrv_write_threshold_is_set(bs)) {
- if (req->offset > bs->write_threshold_offset) {
- return (req->offset - bs->write_threshold_offset) + req->bytes;
- }
- if ((req->offset + req->bytes) > bs->write_threshold_offset) {
- return (req->offset + req->bytes) - bs->write_threshold_offset;
- }
- }
- return 0;
-}
-
-static int coroutine_fn before_write_notify(NotifierWithReturn *notifier,
- void *opaque)
-{
- BdrvTrackedRequest *req = opaque;
- BlockDriverState *bs = req->bs;
- uint64_t amount = 0;
-
- amount = bdrv_write_threshold_exceeded(bs, req);
- if (amount > 0) {
- qapi_event_send_block_write_threshold(
- bs->node_name,
- amount,
- bs->write_threshold_offset);
-
- /* autodisable to avoid flooding the monitor */
- write_threshold_disable(bs);
- }
-
- return 0; /* should always let other notifiers run */
-}
-
-static void write_threshold_register_notifier(BlockDriverState *bs)
-{
- bs->write_threshold_notifier.notify = before_write_notify;
- bdrv_add_before_write_notifier(bs, &bs->write_threshold_notifier);
-}
-
-static void write_threshold_update(BlockDriverState *bs,
- int64_t threshold_bytes)
-{
- bs->write_threshold_offset = threshold_bytes;
+ return qatomic_read(&bs->write_threshold_offset);
}
void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t threshold_bytes)
{
- if (bdrv_write_threshold_is_set(bs)) {
- if (threshold_bytes > 0) {
- write_threshold_update(bs, threshold_bytes);
- } else {
- write_threshold_disable(bs);
- }
- } else {
- if (threshold_bytes > 0) {
- /* avoid multiple registration */
- write_threshold_register_notifier(bs);
- write_threshold_update(bs, threshold_bytes);
- }
- /* discard bogus disable request */
- }
+ qatomic_set(&bs->write_threshold_offset, threshold_bytes);
}
void qmp_block_set_write_threshold(const char *node_name,
uint64_t threshold_bytes,
Error **errp)
{
- BlockDriverState *bs;
- AioContext *aio_context;
-
- bs = bdrv_find_node(node_name);
+ BlockDriverState *bs = bdrv_find_node(node_name);
if (!bs) {
error_setg(errp, "Device '%s' not found", node_name);
return;
}
- aio_context = bdrv_get_aio_context(bs);
- aio_context_acquire(aio_context);
-
bdrv_write_threshold_set(bs, threshold_bytes);
-
- aio_context_release(aio_context);
}
diff --git a/tests/unit/test-write-threshold.c
b/tests/unit/test-write-threshold.c
index fc1c45a2eb..c2f4cd20d7 100644
--- a/tests/unit/test-write-threshold.c
+++ b/tests/unit/test-write-threshold.c
@@ -12,6 +12,44 @@
#include "block/write-threshold.h"
+/*
+ * bdrv_write_threshold_is_set
+ *
+ * Tell if a write threshold is set for a given BDS.
+ */
+static bool bdrv_write_threshold_is_set(const BlockDriverState *bs)
+{
+ return bs->write_threshold_offset > 0;
+}
+
+/*
+ * bdrv_write_threshold_exceeded
+ *
+ * Return the extent of a write request that exceeded the threshold,
+ * or zero if the request is below the threshold.
+ * Return zero also if the threshold was not set.
+ *
+ * NOTE: here we assume the following holds for each request this code
+ * deals with:
+ *
+ * assert((req->offset + req->bytes) <= UINT64_MAX)
+ *
+ * Please not there is *not* an actual C assert().
+ */
+static uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs,
+ const BdrvTrackedRequest *req)
+{
+ if (bdrv_write_threshold_is_set(bs)) {
+ if (req->offset > bs->write_threshold_offset) {
+ return (req->offset - bs->write_threshold_offset) + req->bytes;
+ }
+ if ((req->offset + req->bytes) > bs->write_threshold_offset) {
+ return (req->offset + req->bytes) - bs->write_threshold_offset;
+ }
+ }
+ return 0;
+}
+
static void test_threshold_not_set_on_init(void)
{
uint64_t res;