[Qemu-devel] [PATCH v9 08/17] block/file-posix.c: extend to use io_uring

[Aarushi Mehta <mehta.aaru20@gmail.com>]

Signed-off-by: Aarushi Mehta <mehta.aaru20@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Maxim Levitsky <maximlevitsky@gmail.com>
---
 block/file-posix.c | 99 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 79 insertions(+), 20 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 4479cc7ab4..4aa42f826f 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -156,6 +156,7 @@ typedef struct BDRVRawState {
     bool has_write_zeroes:1;
     bool discard_zeroes:1;
     bool use_linux_aio:1;
+    bool use_linux_io_uring:1;
     bool page_cache_inconsistent:1;
     bool has_fallocate;
     bool needs_alignment;
@@ -425,7 +426,7 @@ static QemuOptsList raw_runtime_opts = {
         {
             .name = "aio",
             .type = QEMU_OPT_STRING,
-            .help = "host AIO implementation (threads, native)",
+            .help = "host AIO implementation (threads, native, io_uring)",
         },
         {
             .name = "locking",
@@ -484,9 +485,15 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
         goto fail;
     }
 
-    aio_default = (bdrv_flags & BDRV_O_NATIVE_AIO)
-                  ? BLOCKDEV_AIO_OPTIONS_NATIVE
-                  : BLOCKDEV_AIO_OPTIONS_THREADS;
+    if (bdrv_flags & BDRV_O_NATIVE_AIO) {
+        aio_default = BLOCKDEV_AIO_OPTIONS_NATIVE;
+#ifdef CONFIG_LINUX_IO_URING
+    } else if (bdrv_flags & BDRV_O_IO_URING) {
+        aio_default = BLOCKDEV_AIO_OPTIONS_IO_URING;
+#endif
+    } else {
+        aio_default = BLOCKDEV_AIO_OPTIONS_THREADS;
+    }
     aio = qapi_enum_parse(&BlockdevAioOptions_lookup,
                           qemu_opt_get(opts, "aio"),
                           aio_default, &local_err);
@@ -495,7 +502,11 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
         ret = -EINVAL;
         goto fail;
     }
+
     s->use_linux_aio = (aio == BLOCKDEV_AIO_OPTIONS_NATIVE);
+#ifdef CONFIG_LINUX_IO_URING
+    s->use_linux_io_uring = (aio == BLOCKDEV_AIO_OPTIONS_IO_URING);
+#endif
 
     locking = qapi_enum_parse(&OnOffAuto_lookup,
                               qemu_opt_get(opts, "locking"),
@@ -559,7 +570,7 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
     s->shared_perm = BLK_PERM_ALL;
 
 #ifdef CONFIG_LINUX_AIO
-     /* Currently Linux does AIO only for files opened with O_DIRECT */
+    /* Currently Linux does AIO only for files opened with O_DIRECT */
     if (s->use_linux_aio) {
         if (!(s->open_flags & O_DIRECT)) {
             error_setg(errp, "aio=native was specified, but it requires "
@@ -581,6 +592,22 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
     }
 #endif /* !defined(CONFIG_LINUX_AIO) */
 
+#ifdef CONFIG_LINUX_IO_URING
+    if (s->use_linux_io_uring) {
+        if (!aio_setup_linux_io_uring(bdrv_get_aio_context(bs), errp)) {
+            error_prepend(errp, "Unable to use io_uring: ");
+            goto fail;
+        }
+    }
+#else
+    if (s->use_linux_io_uring) {
+        error_setg(errp, "aio=io_uring was specified, but is not supported "
+                         "in this build.");
+        ret = -EINVAL;
+        goto fail;
+    }
+#endif /* !defined(CONFIG_LINUX_IO_URING) */
+
     s->has_discard = true;
     s->has_write_zeroes = true;
     if ((bs->open_flags & BDRV_O_NOCACHE) != 0) {
@@ -1874,21 +1901,25 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, uint64_t offset,
         return -EIO;
 
     /*
-     * Check if the underlying device requires requests to be aligned,
-     * and if the request we are trying to submit is aligned or not.
-     * If this is the case tell the low-level driver that it needs
-     * to copy the buffer.
+     * When using O_DIRECT, the request must be aligned to be able to use
+     * either libaio or io_uring interface. If not fail back to regular thread
+     * pool read/write code which emulates this for us if we
+     * set QEMU_AIO_MISALIGNED.
      */
-    if (s->needs_alignment) {
-        if (!bdrv_qiov_is_aligned(bs, qiov)) {
-            type |= QEMU_AIO_MISALIGNED;
+    if (s->needs_alignment && !bdrv_qiov_is_aligned(bs, qiov)) {
+        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);
+#endif
 #ifdef CONFIG_LINUX_AIO
-        } else if (s->use_linux_aio) {
-            LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
-            assert(qiov->size == bytes);
-            return laio_co_submit(bs, aio, s->fd, offset, qiov, type);
+    } else if (s->use_linux_aio) {
+        LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
+        assert(qiov->size == bytes);
+        return laio_co_submit(bs, aio, s->fd, offset, qiov, type);
 #endif
-        }
     }
 
     acb = (RawPosixAIOData) {
@@ -1924,24 +1955,36 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset,
 
 static void raw_aio_plug(BlockDriverState *bs)
 {
+    BDRVRawState __attribute__((unused)) *s = bs->opaque;
 #ifdef CONFIG_LINUX_AIO
-    BDRVRawState *s = bs->opaque;
     if (s->use_linux_aio) {
         LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
         laio_io_plug(bs, aio);
     }
 #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);
+    }
+#endif
 }
 
 static void raw_aio_unplug(BlockDriverState *bs)
 {
+    BDRVRawState __attribute__((unused)) *s = bs->opaque;
 #ifdef CONFIG_LINUX_AIO
-    BDRVRawState *s = bs->opaque;
     if (s->use_linux_aio) {
         LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
         laio_io_unplug(bs, aio);
     }
 #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);
+    }
+#endif
 }
 
 static int raw_co_flush_to_disk(BlockDriverState *bs)
@@ -1961,14 +2004,20 @@ static int raw_co_flush_to_disk(BlockDriverState *bs)
         .aio_type       = QEMU_AIO_FLUSH,
     };
 
+#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);
+    }
+#endif
     return raw_thread_pool_submit(bs, handle_aiocb_flush, &acb);
 }
 
 static void raw_aio_attach_aio_context(BlockDriverState *bs,
                                        AioContext *new_context)
 {
+    BDRVRawState __attribute__((unused)) *s = bs->opaque;
 #ifdef CONFIG_LINUX_AIO
-    BDRVRawState *s = bs->opaque;
     if (s->use_linux_aio) {
         Error *local_err;
         if (!aio_setup_linux_aio(new_context, &local_err)) {
@@ -1978,6 +2027,16 @@ static void raw_aio_attach_aio_context(BlockDriverState *bs,
         }
     }
 #endif
+#ifdef CONFIG_LINUX_IO_URING
+    if (s->use_linux_io_uring) {
+        Error *local_err;
+        if (!aio_setup_linux_io_uring(new_context, &local_err)) {
+            error_reportf_err(local_err, "Unable to use linux io_uring, "
+                                         "falling back to thread pool: ");
+            s->use_linux_io_uring = false;
+        }
+    }
+#endif
 }
 
 static void raw_close(BlockDriverState *bs)
-- 
2.21.0