[PATCH v3 2/3] io_uring: use LuringState from the running thread

[Emanuele Giuseppe Esposito]

Remove usage of aio_context_acquire by always submitting asynchronous
AIO to the current thread's LuringState.

In order to prevent mistakes from the caller side, avoid passing LuringState
in luring_io_{plug/unplug} and luring_co_submit.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block/file-posix.c      | 12 ++++--------
 block/io_uring.c        | 22 ++++++++++++++--------
 include/block/aio.h     |  4 ----
 include/block/raw-aio.h |  8 ++++----
 4 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 23fe98eb3e..3800dbd222 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2093,9 +2093,8 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, 
uint64_t offset,
         type |= QEMU_AIO_MISALIGNED;
 #ifdef CONFIG_LINUX_IO_URING
     } else if (s->use_linux_io_uring) {
-        LuringState *aio = aio_get_linux_io_uring(bdrv_get_aio_context(bs));
         assert(qiov->size == bytes);
-        return luring_co_submit(bs, aio, s->fd, offset, qiov, type);
+        return luring_co_submit(bs, s->fd, offset, qiov, type);
 #endif
 #ifdef CONFIG_LINUX_AIO
     } else if (s->use_linux_aio) {
@@ -2145,8 +2144,7 @@ static void raw_aio_plug(BlockDriverState *bs)
 #endif
 #ifdef CONFIG_LINUX_IO_URING
     if (s->use_linux_io_uring) {
-        LuringState *aio = aio_get_linux_io_uring(bdrv_get_aio_context(bs));
-        luring_io_plug(bs, aio);
+        luring_io_plug();
     }
 #endif
 }
@@ -2161,8 +2159,7 @@ static void raw_aio_unplug(BlockDriverState *bs)
 #endif
 #ifdef CONFIG_LINUX_IO_URING
     if (s->use_linux_io_uring) {
-        LuringState *aio = aio_get_linux_io_uring(bdrv_get_aio_context(bs));
-        luring_io_unplug(bs, aio);
+        luring_io_unplug();
     }
 #endif
 }
@@ -2186,8 +2183,7 @@ static int coroutine_fn 
raw_co_flush_to_disk(BlockDriverState *bs)
 
 #ifdef CONFIG_LINUX_IO_URING
     if (s->use_linux_io_uring) {
-        LuringState *aio = aio_get_linux_io_uring(bdrv_get_aio_context(bs));
-        return luring_co_submit(bs, aio, s->fd, 0, NULL, QEMU_AIO_FLUSH);
+        return luring_co_submit(bs, s->fd, 0, NULL, QEMU_AIO_FLUSH);
     }
 #endif
     return raw_thread_pool_submit(bs, handle_aiocb_flush, &acb);
diff --git a/block/io_uring.c b/block/io_uring.c
index a1760152e0..df1f076cb9 100644
--- a/block/io_uring.c
+++ b/block/io_uring.c
@@ -19,6 +19,8 @@
 #include "qapi/error.h"
 #include "trace.h"
 
+/* Only used for assertions.  */
+#include "qemu/coroutine_int.h"
 
 /* io_uring ring size */
 #define MAX_ENTRIES 128
@@ -52,10 +54,9 @@ typedef struct LuringState {
 
     struct io_uring ring;
 
-    /* io queue for submit at batch.  Protected by AioContext lock. */
+    /* All data is only used in one I/O thread.  */
     LuringQueue io_q;
 
-    /* I/O completion processing.  Only runs in I/O thread.  */
     QEMUBH *completion_bh;
 } LuringState;
 
@@ -211,6 +212,7 @@ end:
          * eventually runs later. Coroutines cannot be entered recursively
          * so avoid doing that!
          */
+        assert(luringcb->co->ctx == luringcb->aio_context);
         if (!qemu_coroutine_entered(luringcb->co)) {
             aio_co_wake(luringcb->co);
         }
@@ -264,13 +266,11 @@ static int ioq_submit(LuringState *s)
 
 static void luring_process_completions_and_submit(LuringState *s)
 {
-    aio_context_acquire(s->aio_context);
     luring_process_completions(s);
 
     if (!s->io_q.plugged && s->io_q.in_queue > 0) {
         ioq_submit(s);
     }
-    aio_context_release(s->aio_context);
 }
 
 static void qemu_luring_completion_bh(void *opaque)
@@ -308,14 +308,18 @@ static void ioq_init(LuringQueue *io_q)
     io_q->blocked = false;
 }
 
-void luring_io_plug(BlockDriverState *bs, LuringState *s)
+void luring_io_plug(void)
 {
+    AioContext *ctx = qemu_get_current_aio_context();
+    LuringState *s = aio_get_linux_io_uring(ctx);
     trace_luring_io_plug(s);
     s->io_q.plugged++;
 }
 
-void luring_io_unplug(BlockDriverState *bs, LuringState *s)
+void luring_io_unplug(void)
 {
+    AioContext *ctx = qemu_get_current_aio_context();
+    LuringState *s = aio_get_linux_io_uring(ctx);
     assert(s->io_q.plugged);
     trace_luring_io_unplug(s, s->io_q.blocked, s->io_q.plugged,
                            s->io_q.in_queue, s->io_q.in_flight);
@@ -375,10 +379,12 @@ static int luring_do_submit(int fd, LuringAIOCB 
*luringcb, LuringState *s,
     return 0;
 }
 
-int coroutine_fn luring_co_submit(BlockDriverState *bs, LuringState *s, int fd,
-                                  uint64_t offset, QEMUIOVector *qiov, int 
type)
+int coroutine_fn luring_co_submit(BlockDriverState *bs, int fd, uint64_t 
offset,
+                                  QEMUIOVector *qiov, int type)
 {
     int ret;
+    AioContext *ctx = qemu_get_current_aio_context();
+    LuringState *s = aio_get_linux_io_uring(ctx);
     LuringAIOCB luringcb = {
         .co         = qemu_coroutine_self(),
         .ret        = -EINPROGRESS,
diff --git a/include/block/aio.h b/include/block/aio.h
index 8bb5eea4a9..15375ff63a 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -203,10 +203,6 @@ struct AioContext {
     struct LinuxAioState *linux_aio;
 #endif
 #ifdef CONFIG_LINUX_IO_URING
-    /*
-     * State for Linux io_uring.  Uses aio_context_acquire/release for
-     * locking.
-     */
     struct LuringState *linux_io_uring;
 
     /* State for file descriptor monitoring using Linux io_uring */
diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h
index f0f14f14f8..4d6b0ee125 100644
--- a/include/block/raw-aio.h
+++ b/include/block/raw-aio.h
@@ -62,12 +62,12 @@ void laio_io_unplug(uint64_t dev_max_batch);
 typedef struct LuringState LuringState;
 LuringState *luring_init(Error **errp);
 void luring_cleanup(LuringState *s);
-int coroutine_fn luring_co_submit(BlockDriverState *bs, LuringState *s, int fd,
-                                uint64_t offset, QEMUIOVector *qiov, int type);
+int coroutine_fn luring_co_submit(BlockDriverState *bs, int fd, uint64_t 
offset,
+                                  QEMUIOVector *qiov, int type);
 void luring_detach_aio_context(LuringState *s, AioContext *old_context);
 void luring_attach_aio_context(LuringState *s, AioContext *new_context);
-void luring_io_plug(BlockDriverState *bs, LuringState *s);
-void luring_io_unplug(BlockDriverState *bs, LuringState *s);
+void luring_io_plug(void);
+void luring_io_unplug(void);
 #endif
 
 #ifdef _WIN32
-- 
2.31.1