[QEMU HCI-8.0 PATCH v2 2/5] vhost-blk: change backend setup

[Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>]

Previously we used very ugly and incapsulation-breaking assignment
fd = blk_bs(s->conf.conf.blk)->file->bs->opaque;
It is wrong in a many ways, so let's rework this.

Patch changes default `drive` to new `devpath` option so device fd
is managed by vhost-blk itself. Unfortunately this way we need a
bit more preparational work: finding out disk length, etc. Don't
be too broad and just do the minimal work. Drop the generic block
device properties along with the block node: the kernel module
does all IO in terms of 512 sectors, so simply report 512 byte
logical/physical block size to the guest.
Also we lose resize, as this is tied to the block node, which is
now have no place in the setup. We will add this in the next
patches as well as RO mode.

https://virtuozzo.atlassian.net/browse/VSTOR-143437
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>
---
v2:
 - moved double close fix to  'do not double close vhostfd' patch
 - dropped DEFINE_BLOCK_PROPERTIES_BASE exposition to the outside. Let's
just use defaults for now. We can later check if tweaking this values
makes any difference and add them back.
 - change vhost_blk_update_size() to return zero or error and move 'changed'
to a separate argument
 - changed lseek to BLKGETSIZE64 (we already use BLKROGET anyway)

 hw/block/vhost-blk.c          | 126 ++++++++++++++++++++--------------
 include/hw/virtio/vhost-blk.h |   5 +-
 2 files changed, 78 insertions(+), 53 deletions(-)

diff --git a/hw/block/vhost-blk.c b/hw/block/vhost-blk.c
index 9bd49fef2d..24f4fbe2b6 100644
--- a/hw/block/vhost-blk.c
+++ b/hw/block/vhost-blk.c
@@ -24,23 +24,17 @@
 #include "system/system.h"
 #include "linux-headers/linux/vhost.h"
 #include <sys/ioctl.h>
-#include <linux/fs.h>
-#include "include/block/block_int-common.h"
 #include "system/runstate.h"
 
 static int vhost_blk_start(VirtIODevice *vdev)
 {
     VHostBlk *s = VHOST_BLK(vdev);
     struct vhost_vring_file backend;
-    int ret, i, nworkers, *fd;
+    int ret, i, nworkers;
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     char serial[VIRTIO_BLK_ID_BYTES] = {0};
 
-    bdrv_graph_rdlock_main_loop();
-    fd = blk_bs(s->conf.conf.blk)->file->bs->opaque;
-    bdrv_graph_rdunlock_main_loop();
-
     if (!k->set_guest_notifiers) {
         error_report("vhost-blk: binding does not support guest notifiers");
         return -ENOSYS;
@@ -92,7 +86,7 @@ static int vhost_blk_start(VirtIODevice *vdev)
 
     memset(&backend, 0, sizeof(backend));
     backend.index = 0;
-    backend.fd = *fd;
+    backend.fd = s->backend_fd;
     if (ioctl(s->vhostfd, VHOST_BLK_SET_BACKEND, &backend)) {
         error_report("vhost-blk: unable to set backend");
         ret = -errno;
@@ -208,29 +202,69 @@ static void vhost_blk_vm_state(void *opaque, bool running, RunState state)
     }
 }
 
-static void vhost_blk_resize_cb(void *opaque)
+static int vhost_blk_update_size(VHostBlk *s, bool *changed, Error **errp)
 {
-    VirtIODevice *vdev = opaque;
+    BlockConf *conf = &s->conf.conf;
+    uint64_t length;
+
+    if (ioctl(s->backend_fd, BLKGETSIZE64, &length) < 0) {
+        int error = errno;
+
+        error_setg_errno(errp, error,
+                         "vhost-blk: unable to determine size of '%s'",
+                         s->conf.devpath);
+        return -error;
+    }
+
+    *changed = s->length != length;
+    s->length = length;
+    conf->heads = 16;
+    conf->secs = 63;
+    conf->cyls = s->length / BDRV_SECTOR_SIZE /
+                 (conf->heads * conf->secs);
+    conf->cyls = MIN(MAX(conf->cyls, 2U), 16383U);
 
-    assert(qemu_get_current_aio_context() == qemu_get_aio_context());
-    virtio_notify_config(vdev);
+    return 0;
 }
 
-static void vhost_blk_resize(void *opaque)
+static bool vhost_blk_open_backend(VHostBlk *s, Error **errp)
 {
-    VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
+    BlockConf *conf = &s->conf.conf;
+    struct stat st;
+    bool changed;
 
-    /*
-     * virtio_notify_config() needs to acquire the global mutex,
-     * so it can't be called from an iothread. Instead, schedule
-     * it to be run in the main context BH.
-     */
-    aio_bh_schedule_oneshot(qemu_get_aio_context(), vhost_blk_resize_cb, vdev);
-}
+    s->backend_fd = qemu_open(s->conf.devpath, O_RDWR, errp);
+    if (s->backend_fd < 0) {
+        error_prepend(errp, "vhost-blk: unable to open backend: ");
+        return false;
+    }
 
-static const BlockDevOps vhost_blk_block_ops = {
-    .resize_cb     = vhost_blk_resize,
-};
+    if (fstat(s->backend_fd, &st) < 0) {
+        error_setg_errno(errp, errno, "vhost-blk: unable to stat '%s'",
+                         s->conf.devpath);
+        goto fail;
+    }
+
+    if (!S_ISBLK(st.st_mode)) {
+        error_setg(errp, "vhost-blk: '%s' is not a block device",
+                   s->conf.devpath);
+        goto fail;
+    }
+
+    if (vhost_blk_update_size(s, &changed, errp) < 0) {
+        goto fail;
+    }
+
+    conf->logical_block_size = BDRV_SECTOR_SIZE;
+    conf->physical_block_size = BDRV_SECTOR_SIZE;
+
+    return true;
+
+fail:
+    qemu_close(s->backend_fd);
+    s->backend_fd = -1;
+    return false;
+}
 
 static void vhost_blk_device_realize(DeviceState *dev, Error **errp)
 {
@@ -239,13 +273,8 @@ static void vhost_blk_device_realize(DeviceState *dev, Error **errp)
     VhostBlkConf *conf = &s->conf;
     int i, ret;
 
-    if (!conf->conf.blk) {
-        error_setg(errp, "vhost-blk: drive property not set");
-        return;
-    }
-
-    if (!blk_is_inserted(conf->conf.blk)) {
-        error_setg(errp, "vhost-blk: device needs media, but drive is empty");
+    if (!conf->devpath) {
+        error_setg(errp, "vhost-blk: devpath property must be set");
         return;
     }
 
@@ -273,17 +302,7 @@ static void vhost_blk_device_realize(DeviceState *dev, Error **errp)
         return;
     }
 
-    if (!blkconf_apply_backend_options(&conf->conf,
-                                       !blk_supports_write_perm(conf->conf.blk),
-                                       true, errp)) {
-        return;
-    }
-
-    if (!blkconf_geometry(&conf->conf, NULL, 65535, 255, 255, errp)) {
-        return;
-    }
-
-    if (!blkconf_blocksizes(&conf->conf, errp)) {
+    if (!vhost_blk_open_backend(s, errp)) {
         return;
     }
 
@@ -311,8 +330,6 @@ static void vhost_blk_device_realize(DeviceState *dev, Error **errp)
         goto cleanup;
     }
 
-    blk_set_dev_ops(s->conf.conf.blk, &vhost_blk_block_ops, s);
-
     ret = vhost_dev_init(&s->dev, (void *)((size_t)s->vhostfd),
                          VHOST_BACKEND_TYPE_KERNEL, 0, NULL);
     if (ret < 0) {
@@ -334,6 +351,10 @@ cleanup:
         close(s->vhostfd);
         s->vhostfd = -1;
     }
+    if (s->backend_fd >= 0) {
+        qemu_close(s->backend_fd);
+        s->backend_fd = -1;
+    }
     for (i = 0; i < conf->num_queues; i++) {
         virtio_del_queue(vdev, i);
     }
@@ -349,6 +370,10 @@ static void vhost_blk_device_unrealize(DeviceState *dev)
     qemu_del_vm_change_state_handler(s->mighand);
     vhost_blk_set_status(vdev, 0);
     vhost_dev_cleanup(&s->dev);
+    if (s->backend_fd >= 0) {
+        qemu_close(s->backend_fd);
+        s->backend_fd = -1;
+    }
     g_free(s->dev.vqs);
     virtio_cleanup(vdev);
 }
@@ -381,10 +406,6 @@ static uint64_t vhost_blk_get_features(VirtIODevice *vdev,
 
     virtio_add_feature(&features, VIRTIO_F_VERSION_1);
 
-    if (!blk_is_writable(s->conf.conf.blk)) {
-        virtio_add_feature(&features, VIRTIO_BLK_F_RO);
-    }
-
     if (s->conf.num_queues > 1) {
         virtio_add_feature(&features, VIRTIO_BLK_F_MQ);
     }
@@ -403,7 +424,9 @@ static void vhost_blk_update_config(VirtIODevice *vdev, uint8_t *config)
     int64_t length;
     int blk_size = conf->logical_block_size;
 
-    blk_get_geometry(s->conf.conf.blk, &capacity);
+    length = s->length;
+    capacity = length / BDRV_SECTOR_SIZE;
+
     memset(&blkcfg, 0, sizeof(blkcfg));
     virtio_stq_p(vdev, &blkcfg.capacity, capacity);
     virtio_stl_p(vdev, &blkcfg.seg_max, s->conf.queue_size - 2);
@@ -411,7 +434,6 @@ static void vhost_blk_update_config(VirtIODevice *vdev, uint8_t *config)
     virtio_stl_p(vdev, &blkcfg.blk_size, blk_size);
     blkcfg.geometry.heads = conf->heads;
 
-    length = blk_getlength(s->conf.conf.blk);
     if (length > 0 && length / conf->heads / conf->secs % blk_size) {
         unsigned short mask;
 
@@ -430,7 +452,7 @@ static void vhost_blk_update_config(VirtIODevice *vdev, uint8_t *config)
 }
 
 static const Property vhost_blk_properties[] = {
-    DEFINE_BLOCK_PROPERTIES(VHostBlk, conf.conf),
+    DEFINE_PROP_STRING("devpath", VHostBlk, conf.devpath),
     DEFINE_PROP_UINT16("num-queues", VHostBlk, conf.num_queues,
                        VHOST_BLK_AUTO_NUM_QUEUES),
     DEFINE_PROP_UINT16("queue-size", VHostBlk, conf.queue_size, 256),
@@ -475,6 +497,8 @@ static void vhost_blk_instance_init(Object *obj)
 {
     VHostBlk *s = VHOST_BLK(obj);
 
+    s->vhostfd = -1;
+    s->backend_fd = -1;
     device_add_bootindex_property(obj, &s->conf.conf.bootindex,
                                   "bootindex", "/disk@0,0",
                                   DEVICE(obj));
diff --git a/include/hw/virtio/vhost-blk.h b/include/hw/virtio/vhost-blk.h
index 0c7e212595..c194b421d9 100644
--- a/include/hw/virtio/vhost-blk.h
+++ b/include/hw/virtio/vhost-blk.h
@@ -14,7 +14,6 @@
 #include "standard-headers/linux/virtio_blk.h"
 #include "hw/block/block.h"
 #include "hw/virtio/vhost.h"
-#include "system/block-backend.h"
 
 #define TYPE_VHOST_BLK "vhost-blk"
 #define VHOST_BLK(obj) \
@@ -25,6 +24,7 @@
 
 typedef struct VhostBlkConf {
     BlockConf conf;
+    char *devpath;
     uint16_t num_queues;
     uint16_t queue_size;
     uint16_t num_threads;
@@ -37,10 +37,11 @@ typedef struct VHostBlk {
     VMChangeStateEntry *mighand;
     uint64_t host_features;
     uint64_t decided_features;
-    struct virtio_blk_config blkcfg;
     int vhostfd;
+    int backend_fd;
     struct vhost_dev dev;
     bool vhost_started;
+    uint64_t length;
 } VHostBlk;
 
 #endif
-- 
2.43.5