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qemu-kvm/SOURCES/kvm-block-file-posix-set-up-Linux-AIO-and-io_uring-in-th.patch

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From 25cce5df341861e8ba8ec57722558e2dee3ce56a Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 14 Sep 2023 10:00:58 -0400
Subject: [PATCH 073/101] block/file-posix: set up Linux AIO and io_uring in
the current thread
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: [4/26] 74c7daf805daefe706378308c3afeb28d861164b (kmwolf/centos-qemu-kvm)
The file-posix block driver currently only sets up Linux AIO and
io_uring in the BDS's AioContext. In the multi-queue block layer we must
be able to submit I/O requests in AioContexts that do not have Linux AIO
and io_uring set up yet since any thread can call into the block driver.
Set up Linux AIO and io_uring for the current AioContext during request
submission. We lose the ability to return an error from
.bdrv_file_open() when Linux AIO and io_uring setup fails (e.g. due to
resource limits). Instead the user only gets warnings and we fall back
to aio=threads. This is still better than a fatal error after startup.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230914140101.1065008-2-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/file-posix.c | 103 ++++++++++++++++++++++-----------------------
1 file changed, 51 insertions(+), 52 deletions(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index b862406c71..35684f7e21 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -712,17 +712,11 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
#ifdef CONFIG_LINUX_AIO
/* 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 "
- "cache.direct=on, which was not specified.");
- ret = -EINVAL;
- goto fail;
- }
- if (!aio_setup_linux_aio(bdrv_get_aio_context(bs), errp)) {
- error_prepend(errp, "Unable to use native AIO: ");
- goto fail;
- }
+ if (s->use_linux_aio && !(s->open_flags & O_DIRECT)) {
+ error_setg(errp, "aio=native was specified, but it requires "
+ "cache.direct=on, which was not specified.");
+ ret = -EINVAL;
+ goto fail;
}
#else
if (s->use_linux_aio) {
@@ -733,14 +727,7 @@ 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
+#ifndef CONFIG_LINUX_IO_URING
if (s->use_linux_io_uring) {
error_setg(errp, "aio=io_uring was specified, but is not supported "
"in this build.");
@@ -2444,6 +2431,48 @@ static bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
return true;
}
+#ifdef CONFIG_LINUX_IO_URING
+static inline bool raw_check_linux_io_uring(BDRVRawState *s)
+{
+ Error *local_err = NULL;
+ AioContext *ctx;
+
+ if (!s->use_linux_io_uring) {
+ return false;
+ }
+
+ ctx = qemu_get_current_aio_context();
+ if (unlikely(!aio_setup_linux_io_uring(ctx, &local_err))) {
+ error_reportf_err(local_err, "Unable to use linux io_uring, "
+ "falling back to thread pool: ");
+ s->use_linux_io_uring = false;
+ return false;
+ }
+ return true;
+}
+#endif
+
+#ifdef CONFIG_LINUX_AIO
+static inline bool raw_check_linux_aio(BDRVRawState *s)
+{
+ Error *local_err = NULL;
+ AioContext *ctx;
+
+ if (!s->use_linux_aio) {
+ return false;
+ }
+
+ ctx = qemu_get_current_aio_context();
+ if (unlikely(!aio_setup_linux_aio(ctx, &local_err))) {
+ error_reportf_err(local_err, "Unable to use Linux AIO, "
+ "falling back to thread pool: ");
+ s->use_linux_aio = false;
+ return false;
+ }
+ return true;
+}
+#endif
+
static int coroutine_fn raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr,
uint64_t bytes, QEMUIOVector *qiov, int type)
{
@@ -2474,13 +2503,13 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr,
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) {
+ } else if (raw_check_linux_io_uring(s)) {
assert(qiov->size == bytes);
ret = luring_co_submit(bs, s->fd, offset, qiov, type);
goto out;
#endif
#ifdef CONFIG_LINUX_AIO
- } else if (s->use_linux_aio) {
+ } else if (raw_check_linux_aio(s)) {
assert(qiov->size == bytes);
ret = laio_co_submit(s->fd, offset, qiov, type,
s->aio_max_batch);
@@ -2567,39 +2596,13 @@ static int coroutine_fn raw_co_flush_to_disk(BlockDriverState *bs)
};
#ifdef CONFIG_LINUX_IO_URING
- if (s->use_linux_io_uring) {
+ if (raw_check_linux_io_uring(s)) {
return luring_co_submit(bs, s->fd, 0, NULL, QEMU_AIO_FLUSH);
}
#endif
return raw_thread_pool_submit(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
- if (s->use_linux_aio) {
- Error *local_err = NULL;
- if (!aio_setup_linux_aio(new_context, &local_err)) {
- error_reportf_err(local_err, "Unable to use native AIO, "
- "falling back to thread pool: ");
- s->use_linux_aio = false;
- }
- }
-#endif
-#ifdef CONFIG_LINUX_IO_URING
- if (s->use_linux_io_uring) {
- Error *local_err = NULL;
- 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)
{
BDRVRawState *s = bs->opaque;
@@ -3896,7 +3899,6 @@ BlockDriver bdrv_file = {
.bdrv_co_copy_range_from = raw_co_copy_range_from,
.bdrv_co_copy_range_to = raw_co_copy_range_to,
.bdrv_refresh_limits = raw_refresh_limits,
- .bdrv_attach_aio_context = raw_aio_attach_aio_context,
.bdrv_co_truncate = raw_co_truncate,
.bdrv_co_getlength = raw_co_getlength,
@@ -4266,7 +4268,6 @@ static BlockDriver bdrv_host_device = {
.bdrv_co_copy_range_from = raw_co_copy_range_from,
.bdrv_co_copy_range_to = raw_co_copy_range_to,
.bdrv_refresh_limits = raw_refresh_limits,
- .bdrv_attach_aio_context = raw_aio_attach_aio_context,
.bdrv_co_truncate = raw_co_truncate,
.bdrv_co_getlength = raw_co_getlength,
@@ -4402,7 +4403,6 @@ static BlockDriver bdrv_host_cdrom = {
.bdrv_co_pwritev = raw_co_pwritev,
.bdrv_co_flush_to_disk = raw_co_flush_to_disk,
.bdrv_refresh_limits = cdrom_refresh_limits,
- .bdrv_attach_aio_context = raw_aio_attach_aio_context,
.bdrv_co_truncate = raw_co_truncate,
.bdrv_co_getlength = raw_co_getlength,
@@ -4528,7 +4528,6 @@ static BlockDriver bdrv_host_cdrom = {
.bdrv_co_pwritev = raw_co_pwritev,
.bdrv_co_flush_to_disk = raw_co_flush_to_disk,
.bdrv_refresh_limits = cdrom_refresh_limits,
- .bdrv_attach_aio_context = raw_aio_attach_aio_context,
.bdrv_co_truncate = raw_co_truncate,
.bdrv_co_getlength = raw_co_getlength,
--
2.39.3
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