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linux-aio: properly bubble up errors from initialization

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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
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12
block/linux-aio.c
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;
}