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block/file-posix: set up Linux AIO and io_uring in the current thread 
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>
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Stefan Hajnoczi authored and Kevin Wolf committed Dec 21, 2023
1 parent 7075d23 commit f3aafd0
Showing 1 changed file with 47 additions and 52 deletions.
99 changes: 47 additions & 52 deletions block/file-posix.c
View file
Expand Up @@ -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) {
Expand All @@ -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.");
Expand Down Expand Up @@ -2444,6 +2431,44 @@ static bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
return true;
}

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;
}

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;
}

static int coroutine_fn raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr,
uint64_t bytes, QEMUIOVector *qiov, int type)
{
Expand Down Expand Up @@ -2474,13 +2499,13 @@ 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);
Expand Down Expand Up @@ -2567,39 +2592,13 @@ 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;
Expand Down Expand Up @@ -3896,7 +3895,6 @@ 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,
Expand Down Expand Up @@ -4266,7 +4264,6 @@ 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,
Expand Down Expand Up @@ -4402,7 +4399,6 @@ 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,
Expand Down Expand Up @@ -4528,7 +4524,6 @@ 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,
Expand Down

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