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qemu-kvm/SOURCES/kvm-virtio-blk-add-lock-to-protect-s-rq.patch

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From d54e88103aa76f3bf755b3f4308d8ab60367c6ef Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 14 Sep 2023 10:00:59 -0400
Subject: [PATCH 074/101] virtio-blk: add lock to protect s->rq
RH-Author: Kevin Wolf <kwolf@redhat.com>
RH-MergeRequest: 214: Remove AioContext lock
RH-Jira: RHEL-15965
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Commit: [5/26] 17dcd5ba18c03e5633a014d8d62d34d8dd7b43bf (kmwolf/centos-qemu-kvm)
s->rq is accessed from IO_CODE and GLOBAL_STATE_CODE. Introduce a lock
to protect s->rq and eliminate reliance on the AioContext lock.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230914140101.1065008-3-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
hw/block/virtio-blk.c | 67 +++++++++++++++++++++++-----------
include/hw/virtio/virtio-blk.h | 3 +-
2 files changed, 47 insertions(+), 23 deletions(-)
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index a1f8e15522..ee38e089bc 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -82,8 +82,11 @@ static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
/* Break the link as the next request is going to be parsed from the
* ring again. Otherwise we may end up doing a double completion! */
req->mr_next = NULL;
- req->next = s->rq;
- s->rq = req;
+
+ WITH_QEMU_LOCK_GUARD(&s->rq_lock) {
+ req->next = s->rq;
+ s->rq = req;
+ }
} else if (action == BLOCK_ERROR_ACTION_REPORT) {
virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
if (acct_failed) {
@@ -1183,10 +1186,13 @@ static void virtio_blk_dma_restart_bh(void *opaque)
{
VirtIOBlock *s = opaque;
- VirtIOBlockReq *req = s->rq;
+ VirtIOBlockReq *req;
MultiReqBuffer mrb = {};
- s->rq = NULL;
+ WITH_QEMU_LOCK_GUARD(&s->rq_lock) {
+ req = s->rq;
+ s->rq = NULL;
+ }
aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
while (req) {
@@ -1238,22 +1244,29 @@ static void virtio_blk_reset(VirtIODevice *vdev)
AioContext *ctx;
VirtIOBlockReq *req;
+ /* Dataplane has stopped... */
+ assert(!s->dataplane_started);
+
+ /* ...but requests may still be in flight. */
ctx = blk_get_aio_context(s->blk);
aio_context_acquire(ctx);
blk_drain(s->blk);
+ aio_context_release(ctx);
/* We drop queued requests after blk_drain() because blk_drain() itself can
* produce them. */
- while (s->rq) {
- req = s->rq;
- s->rq = req->next;
- virtqueue_detach_element(req->vq, &req->elem, 0);
- virtio_blk_free_request(req);
- }
+ WITH_QEMU_LOCK_GUARD(&s->rq_lock) {
+ while (s->rq) {
+ req = s->rq;
+ s->rq = req->next;
- aio_context_release(ctx);
+ /* No other threads can access req->vq here */
+ virtqueue_detach_element(req->vq, &req->elem, 0);
+
+ virtio_blk_free_request(req);
+ }
+ }
- assert(!s->dataplane_started);
blk_set_enable_write_cache(s->blk, s->original_wce);
}
@@ -1443,18 +1456,22 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
static void virtio_blk_save_device(VirtIODevice *vdev, QEMUFile *f)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
- VirtIOBlockReq *req = s->rq;
- while (req) {
- qemu_put_sbyte(f, 1);
+ WITH_QEMU_LOCK_GUARD(&s->rq_lock) {
+ VirtIOBlockReq *req = s->rq;
- if (s->conf.num_queues > 1) {
- qemu_put_be32(f, virtio_get_queue_index(req->vq));
- }
+ while (req) {
+ qemu_put_sbyte(f, 1);
- qemu_put_virtqueue_element(vdev, f, &req->elem);
- req = req->next;
+ if (s->conf.num_queues > 1) {
+ qemu_put_be32(f, virtio_get_queue_index(req->vq));
+ }
+
+ qemu_put_virtqueue_element(vdev, f, &req->elem);
+ req = req->next;
+ }
}
+
qemu_put_sbyte(f, 0);
}
@@ -1480,8 +1497,11 @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
req = qemu_get_virtqueue_element(vdev, f, sizeof(VirtIOBlockReq));
virtio_blk_init_request(s, virtio_get_queue(vdev, vq_idx), req);
- req->next = s->rq;
- s->rq = req;
+
+ WITH_QEMU_LOCK_GUARD(&s->rq_lock) {
+ req->next = s->rq;
+ s->rq = req;
+ }
}
return 0;
@@ -1628,6 +1648,8 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
s->host_features);
virtio_init(vdev, VIRTIO_ID_BLOCK, s->config_size);
+ qemu_mutex_init(&s->rq_lock);
+
s->blk = conf->conf.blk;
s->rq = NULL;
s->sector_mask = (s->conf.conf.logical_block_size / BDRV_SECTOR_SIZE) - 1;
@@ -1679,6 +1701,7 @@ static void virtio_blk_device_unrealize(DeviceState *dev)
virtio_del_queue(vdev, i);
}
qemu_coroutine_dec_pool_size(conf->num_queues * conf->queue_size / 2);
+ qemu_mutex_destroy(&s->rq_lock);
blk_ram_registrar_destroy(&s->blk_ram_registrar);
qemu_del_vm_change_state_handler(s->change);
blockdev_mark_auto_del(s->blk);
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index dafec432ce..9881009c22 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -54,7 +54,8 @@ struct VirtIOBlockReq;
struct VirtIOBlock {
VirtIODevice parent_obj;
BlockBackend *blk;
- void *rq;
+ QemuMutex rq_lock;
+ void *rq; /* protected by rq_lock */
VirtIOBlkConf conf;
unsigned short sector_mask;
bool original_wce;
--
2.39.3
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