Series comparison

-[PULL 0/2] Block patches
+[PULL for-6.1 0/3] Block patches
-The following changes since commit 240ab11fb72049d6373cbbec8d788f8e411a00bc:
+The following changes since commit 3521ade3510eb5cefb2e27a101667f25dad89935:
-  Merge remote-tracking branch 'remotes/aperard/tags/pull-xen-20190924' into staging (2019-09-24 15:36:31 +0100)
+  Merge remote-tracking branch 'remotes/thuth-gitlab/tags/pull-request-2021-07-29' into staging (2021-07-29 13:17:20 +0100)
 are available in the Git repository at:
-  https://github.com/stefanha/qemu.git tags/block-pull-request
+  https://gitlab.com/stefanha/qemu.git tags/block-pull-request
-for you to fetch changes up to f9a7e3698a737ee75a7b0af34203303df982550f:
+for you to fetch changes up to cc8eecd7f105a1dff5876adeb238a14696061a4a:
-  virtio-blk: schedule virtio_notify_config to run on main context (2019-09-25 18:06:36 +0100)
+  MAINTAINERS: Added myself as a reviewer for the NVMe Block Driver (2021-07-29 17:17:34 +0100)
 ----------------------------------------------------------------
 Pull request
+The main fix here is for io_uring. Spurious -EAGAIN errors can happen and the
+request needs to be resubmitted.
+The MAINTAINERS changes carry no risk and we might as well include them in QEMU
+.1.
 ----------------------------------------------------------------
-Sergio Lopez (1):
+Fabian Ebner (1):
-  virtio-blk: schedule virtio_notify_config to run on main context
+  block/io_uring: resubmit when result is -EAGAIN
-Vladimir Sementsov-Ogievskiy (1):
+Philippe Mathieu-Daudé (1):
-  util/ioc.c: try to reassure Coverity about qemu_iovec_init_extended
+  MAINTAINERS: Added myself as a reviewer for the NVMe Block Driver
- hw/block/virtio-blk.c | 16 +++++++++++++++-
+Stefano Garzarella (1):
- util/iov.c            |  3 ++-
+  MAINTAINERS: add Stefano Garzarella as io_uring reviewer
-files changed, 17 insertions(+), 2 deletions(-)
  MAINTAINERS      |  2 ++
  block/io_uring.c | 16 +++++++++++++++-
 files changed, 17 insertions(+), 1 deletion(-)
 --
-.21.0
+.31.1

-New patch
+[PULL for-6.1 1/3] MAINTAINERS: add Stefano Garzarella as io_uring reviewer
+From: Stefano Garzarella <sgarzare@redhat.com>
+I've been working with io_uring for a while so I'd like to help
+with reviews.
+Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
+Message-Id: <20210728131515.131045-1-sgarzare@redhat.com>
+Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
+---
+ MAINTAINERS | 1 +
+file changed, 1 insertion(+)
+diff --git a/MAINTAINERS b/MAINTAINERS
+index XXXXXXX..XXXXXXX 100644
+--- a/MAINTAINERS
++++ b/MAINTAINERS
+@@ -XXX,XX +XXX,XX @@ Linux io_uring
+ M: Aarushi Mehta <mehta.aaru20@gmail.com>
+ M: Julia Suvorova <jusual@redhat.com>
+ M: Stefan Hajnoczi <stefanha@redhat.com>
++R: Stefano Garzarella <sgarzare@redhat.com>
+ L: qemu-block@nongnu.org
+ S: Maintained
+ F: block/io_uring.c
+--
+.31.1

-[PULL 2/2] virtio-blk: schedule virtio_notify_config to run on main context
+[PULL for-6.1 2/3] block/io_uring: resubmit when result is -EAGAIN
-From: Sergio Lopez <slp@redhat.com>
+From: Fabian Ebner <f.ebner@proxmox.com>
-virtio_notify_config() needs to acquire the global mutex, which isn't
+Linux SCSI can throw spurious -EAGAIN in some corner cases in its
-allowed from an iothread, and may lead to a deadlock like this:
+completion path, which will end up being the result in the completed
 io_uring request.
- - main thead
+Resubmitting such requests should allow block jobs to complete, even
-  * Has acquired: qemu_global_mutex.
+if such spurious errors are encountered.
   * Is trying the acquire: iothread AioContext lock via
     AIO_WAIT_WHILE (after aio_poll).
- - iothread
+Co-authored-by: Stefan Hajnoczi <stefanha@gmail.com>
-  * Has acquired: AioContext lock.
+Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
-  * Is trying to acquire: qemu_global_mutex (via
+Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
-    virtio_notify_config->prepare_mmio_access).
+Message-id: 20210729091029.65369-1-f.ebner@proxmox.com
 If virtio_blk_resize() is called from an iothread, schedule
 virtio_notify_config() to be run in the main context BH.
 [Removed unnecessary newline as suggested by Kevin Wolf
 <kwolf@redhat.com>.
 --Stefan]
 Signed-off-by: Sergio Lopez <slp@redhat.com>
 Reviewed-by: Kevin Wolf <kwolf@redhat.com>
 Message-id: 20190916112411.21636-1-slp@redhat.com
 Message-Id: <20190916112411.21636-1-slp@redhat.com>
 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
 ---
- hw/block/virtio-blk.c | 16 +++++++++++++++-
+ block/io_uring.c | 16 +++++++++++++++-
 file changed, 15 insertions(+), 1 deletion(-)
-diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
+diff --git a/block/io_uring.c b/block/io_uring.c
 index XXXXXXX..XXXXXXX 100644
---- a/hw/block/virtio-blk.c
+--- a/block/io_uring.c
-+++ b/hw/block/virtio-blk.c
++++ b/block/io_uring.c
-@@ -XXX,XX +XXX,XX @@
+@@ -XXX,XX +XXX,XX @@ static void luring_process_completions(LuringState *s)
- #include "qemu/iov.h"
+         total_bytes = ret + luringcb->total_read;
- #include "qemu/module.h"
- #include "qemu/error-report.h"
+         if (ret < 0) {
-+#include "qemu/main-loop.h"
+-            if (ret == -EINTR) {
- #include "trace.h"
++            /*
- #include "hw/block/block.h"
++             * Only writev/readv/fsync requests on regular files or host block
- #include "hw/qdev-properties.h"
++             * devices are submitted. Therefore -EAGAIN is not expected but it's
-@@ -XXX,XX +XXX,XX @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
++             * known to happen sometimes with Linux SCSI. Submit again and hope
-     return 0;
++             * the request completes successfully.
- }
++             *
++             * For more information, see:
-+static void virtio_resize_cb(void *opaque)
++             * https://lore.kernel.org/io-uring/20210727165811.284510-3-axboe@kernel.dk/T/#u
-+{
++             *
-+    VirtIODevice *vdev = opaque;
++             * If the code is changed to submit other types of requests in the
-+
++             * future, then this workaround may need to be extended to deal with
-+    assert(qemu_get_current_aio_context() == qemu_get_aio_context());
++             * genuine -EAGAIN results that should not be resubmitted
-+    virtio_notify_config(vdev);
++             * immediately.
-+}
++             */
-+
++            if (ret == -EINTR || ret == -EAGAIN) {
- static void virtio_blk_resize(void *opaque)
+                 luring_resubmit(s, luringcb);
- {
+                 continue;
-     VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
+             }
 -    virtio_notify_config(vdev);
 +    /*
 +     * 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(), virtio_resize_cb, vdev);
  }
  static const BlockDevOps virtio_block_ops = {
 --
-.21.0
+.31.1

-[PULL 1/2] util/ioc.c: try to reassure Coverity about qemu_iovec_init_extended
+[PULL for-6.1 3/3] MAINTAINERS: Added myself as a reviewer for the NVMe Block Driver
-From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
+From: Philippe Mathieu-Daudé <philmd@redhat.com>
-Make it more obvious, that filling qiov corresponds to qiov allocation,
+I'm interested in following the activity around the NVMe bdrv.
 which in turn corresponds to total_niov calculation, based on mid_niov
 (not mid_len). Still add an assertion to show that there should be no
 difference.
-Reported-by: Coverity (CID 1405302)
+Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
-Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
+Message-id: 20210728183340.2018313-1-philmd@redhat.com
 Message-id: 20190910090310.14032-1-vsementsov@virtuozzo.com
 Suggested-by: Peter Maydell <peter.maydell@linaro.org>
 Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
 Message-Id: <20190910090310.14032-1-vsementsov@virtuozzo.com>
 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
 ---
- util/iov.c | 3 ++-
+ MAINTAINERS | 1 +
-file changed, 2 insertions(+), 1 deletion(-)
+file changed, 1 insertion(+)
-diff --git a/util/iov.c b/util/iov.c
+diff --git a/MAINTAINERS b/MAINTAINERS
 index XXXXXXX..XXXXXXX 100644
---- a/util/iov.c
+--- a/MAINTAINERS
-+++ b/util/iov.c
++++ b/MAINTAINERS
-@@ -XXX,XX +XXX,XX @@ void qemu_iovec_init_extended(
+@@ -XXX,XX +XXX,XX @@ F: block/null.c
-         p++;
+ NVMe Block Driver
-     }
+ M: Stefan Hajnoczi <stefanha@redhat.com>
+ R: Fam Zheng <fam@euphon.net>
--    if (mid_len) {
++R: Philippe Mathieu-Daudé <philmd@redhat.com>
-+    assert(!mid_niov == !mid_len);
+ L: qemu-block@nongnu.org
-+    if (mid_niov) {
+ S: Supported
-         memcpy(p, mid_iov, mid_niov * sizeof(*p));
+ F: block/nvme*
          p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head;
          p[0].iov_len -= mid_head;
 --
-.21.0
+.31.1

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Make it more obvious, that filling qiov corresponds to qiov allocation,
which in turn corresponds to total_niov calculation, based on mid_niov
(not mid_len). Still add an assertion to show that there should be no
difference.

Reported-by: Coverity (CID 1405302)
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190910090310.14032-1-vsementsov@virtuozzo.com
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190910090310.14032-1-vsementsov@virtuozzo.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 util/iov.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/util/iov.c b/util/iov.c
index XXXXXXX..XXXXXXX 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -XXX,XX +XXX,XX @@ void qemu_iovec_init_extended(
         p++;
     }
 
-    if (mid_len) {
+    assert(!mid_niov == !mid_len);
+    if (mid_niov) {
         memcpy(p, mid_iov, mid_niov * sizeof(*p));
         p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head;
         p[0].iov_len -= mid_head;
-- 
2.21.0

From: Sergio Lopez <slp@redhat.com>

virtio_notify_config() needs to acquire the global mutex, which isn't
allowed from an iothread, and may lead to a deadlock like this:

- main thead
  * Has acquired: qemu_global_mutex.
  * Is trying the acquire: iothread AioContext lock via
    AIO_WAIT_WHILE (after aio_poll).

- iothread
  * Has acquired: AioContext lock.
  * Is trying to acquire: qemu_global_mutex (via
    virtio_notify_config->prepare_mmio_access).

If virtio_blk_resize() is called from an iothread, schedule
virtio_notify_config() to be run in the main context BH.

[Removed unnecessary newline as suggested by Kevin Wolf
<kwolf@redhat.com>.
--Stefan]

Signed-off-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20190916112411.21636-1-slp@redhat.com
Message-Id: <20190916112411.21636-1-slp@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/virtio-blk.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index XXXXXXX..XXXXXXX 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -XXX,XX +XXX,XX @@
 #include "qemu/iov.h"
 #include "qemu/module.h"
 #include "qemu/error-report.h"
+#include "qemu/main-loop.h"
 #include "trace.h"
 #include "hw/block/block.h"
 #include "hw/qdev-properties.h"
@@ -XXX,XX +XXX,XX @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
     return 0;
 }
 
+static void virtio_resize_cb(void *opaque)
+{
+    VirtIODevice *vdev = opaque;
+
+    assert(qemu_get_current_aio_context() == qemu_get_aio_context());
+    virtio_notify_config(vdev);
+}
+
 static void virtio_blk_resize(void *opaque)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
 
-    virtio_notify_config(vdev);
+    /*
+     * 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(), virtio_resize_cb, vdev);
 }
 
 static const BlockDevOps virtio_block_ops = {
-- 
2.21.0

The following changes since commit 3521ade3510eb5cefb2e27a101667f25dad89935:

Merge remote-tracking branch 'remotes/thuth-gitlab/tags/pull-request-2021-07-29' into staging (2021-07-29 13:17:20 +0100)

are available in the Git repository at:

https://gitlab.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to cc8eecd7f105a1dff5876adeb238a14696061a4a:

MAINTAINERS: Added myself as a reviewer for the NVMe Block Driver (2021-07-29 17:17:34 +0100)

----------------------------------------------------------------
Pull request

The main fix here is for io_uring. Spurious -EAGAIN errors can happen and the
request needs to be resubmitted.

The MAINTAINERS changes carry no risk and we might as well include them in QEMU
6.1.

----------------------------------------------------------------

Fabian Ebner (1):
  block/io_uring: resubmit when result is -EAGAIN

Philippe Mathieu-Daudé (1):
  MAINTAINERS: Added myself as a reviewer for the NVMe Block Driver

Stefano Garzarella (1):
  MAINTAINERS: add Stefano Garzarella as io_uring reviewer

MAINTAINERS      |  2 ++
 block/io_uring.c | 16 +++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

-- 
2.31.1

From: Fabian Ebner <f.ebner@proxmox.com>

Linux SCSI can throw spurious -EAGAIN in some corner cases in its
completion path, which will end up being the result in the completed
io_uring request.

Resubmitting such requests should allow block jobs to complete, even
if such spurious errors are encountered.

Co-authored-by: Stefan Hajnoczi <stefanha@gmail.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
Message-id: 20210729091029.65369-1-f.ebner@proxmox.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/io_uring.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/block/io_uring.c b/block/io_uring.c
index XXXXXXX..XXXXXXX 100644
--- a/block/io_uring.c
+++ b/block/io_uring.c
@@ -XXX,XX +XXX,XX @@ static void luring_process_completions(LuringState *s)
         total_bytes = ret + luringcb->total_read;
 
         if (ret < 0) {
-            if (ret == -EINTR) {
+            /*
+             * Only writev/readv/fsync requests on regular files or host block
+             * devices are submitted. Therefore -EAGAIN is not expected but it's
+             * known to happen sometimes with Linux SCSI. Submit again and hope
+             * the request completes successfully.
+             *
+             * For more information, see:
+             * https://lore.kernel.org/io-uring/20210727165811.284510-3-axboe@kernel.dk/T/#u
+             *
+             * If the code is changed to submit other types of requests in the
+             * future, then this workaround may need to be extended to deal with
+             * genuine -EAGAIN results that should not be resubmitted
+             * immediately.
+             */
+            if (ret == -EINTR || ret == -EAGAIN) {
                 luring_resubmit(s, luringcb);
                 continue;
             }
-- 
2.31.1