linux-aio: properly bubble up errors from initialization

laio_init() can fail for a couple of reasons, which will lead to a NULL
pointer dereference in laio_attach_aio_context().

To solve this, add a aio_setup_linux_aio() function which is called
early in raw_open_common. If this fails, propagate the error up. The
signature of aio_get_linux_aio() was not modified, because it seems
preferable to return the actual errno from the possible failing
initialization calls.

Additionally, when the AioContext changes, we need to associate a
LinuxAioState with the new AioContext. Use the bdrv_attach_aio_context
callback and call the new aio_setup_linux_aio(), which will allocate a
new AioContext if needed, and return errors on failures. If it fails for
any reason, fallback to threaded AIO with an error message, as the
device is already in-use by the guest.

Add an assert that aio_get_linux_aio() cannot return NULL.

Signed-off-by: Nishanth Aravamudan <naravamudan@digitalocean.com>
Message-id: 20180622193700.6523-1-naravamudan@digitalocean.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Nishanth Aravamudan 2018-06-22 12:37:00 -07:00 committed by Stefan Hajnoczi
parent f18793b096
commit ed6e216171
6 changed files with 53 additions and 13 deletions

View file

@ -545,11 +545,17 @@ 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 && !(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 (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;
}
}
#else
if (s->use_linux_aio) {
@ -1723,6 +1729,22 @@ static BlockAIOCB *raw_aio_flush(BlockDriverState *bs,
return paio_submit(bs, s->fd, 0, NULL, 0, cb, opaque, QEMU_AIO_FLUSH);
}
static void raw_aio_attach_aio_context(BlockDriverState *bs,
AioContext *new_context)
{
#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)) {
error_reportf_err(local_err, "Unable to use native AIO, "
"falling back to thread pool: ");
s->use_linux_aio = false;
}
}
#endif
}
static void raw_close(BlockDriverState *bs)
{
BDRVRawState *s = bs->opaque;
@ -2601,6 +2623,7 @@ BlockDriver bdrv_file = {
.bdrv_refresh_limits = raw_refresh_limits,
.bdrv_io_plug = raw_aio_plug,
.bdrv_io_unplug = raw_aio_unplug,
.bdrv_attach_aio_context = raw_aio_attach_aio_context,
.bdrv_truncate = raw_truncate,
.bdrv_getlength = raw_getlength,

View file

@ -15,6 +15,7 @@
#include "block/raw-aio.h"
#include "qemu/event_notifier.h"
#include "qemu/coroutine.h"
#include "qapi/error.h"
#include <libaio.h>
@ -470,16 +471,21 @@ void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context)
qemu_laio_poll_cb);
}
LinuxAioState *laio_init(void)
LinuxAioState *laio_init(Error **errp)
{
int rc;
LinuxAioState *s;
s = g_malloc0(sizeof(*s));
if (event_notifier_init(&s->e, false) < 0) {
rc = event_notifier_init(&s->e, false);
if (rc < 0) {
error_setg_errno(errp, -rc, "failed to to initialize event notifier");
goto out_free_state;
}
if (io_setup(MAX_EVENTS, &s->ctx) != 0) {
rc = io_setup(MAX_EVENTS, &s->ctx);
if (rc < 0) {
error_setg_errno(errp, -rc, "failed to create linux AIO context");
goto out_close_efd;
}

View file

@ -381,6 +381,9 @@ GSource *aio_get_g_source(AioContext *ctx);
/* Return the ThreadPool bound to this AioContext */
struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
/* Setup the LinuxAioState bound to this AioContext */
struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp);
/* Return the LinuxAioState bound to this AioContext */
struct LinuxAioState *aio_get_linux_aio(AioContext *ctx);

View file

@ -43,7 +43,7 @@
/* linux-aio.c - Linux native implementation */
#ifdef CONFIG_LINUX_AIO
typedef struct LinuxAioState LinuxAioState;
LinuxAioState *laio_init(void);
LinuxAioState *laio_init(Error **errp);
void laio_cleanup(LinuxAioState *s);
int coroutine_fn laio_co_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
uint64_t offset, QEMUIOVector *qiov, int type);

View file

@ -21,7 +21,7 @@ void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context)
abort();
}
LinuxAioState *laio_init(void)
LinuxAioState *laio_init(Error **errp)
{
abort();
}

View file

@ -323,14 +323,22 @@ ThreadPool *aio_get_thread_pool(AioContext *ctx)
}
#ifdef CONFIG_LINUX_AIO
LinuxAioState *aio_get_linux_aio(AioContext *ctx)
LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp)
{
if (!ctx->linux_aio) {
ctx->linux_aio = laio_init();
laio_attach_aio_context(ctx->linux_aio, ctx);
ctx->linux_aio = laio_init(errp);
if (ctx->linux_aio) {
laio_attach_aio_context(ctx->linux_aio, ctx);
}
}
return ctx->linux_aio;
}
LinuxAioState *aio_get_linux_aio(AioContext *ctx)
{
assert(ctx->linux_aio);
return ctx->linux_aio;
}
#endif
void aio_notify(AioContext *ctx)