Commit ed6e2161 authored by Nishanth Aravamudan's avatar Nishanth Aravamudan Committed by Stefan Hajnoczi
Browse files

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: default avatarNishanth Aravamudan <naravamudan@digitalocean.com>
Message-id: 20180622193700.6523-1-naravamudan@digitalocean.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent f18793b0

block/file-posix.c

+28 −5
Original line number Diff line number Diff line
@@ -545,12 +545,18 @@ 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)) {

    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) {

        error_setg(errp, "aio=native was specified, but is not supported "
@@ -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,

block/linux-aio.c

+9 −3
Original line number Diff line number Diff line
@@ -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;

    }

include/block/aio.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

include/block/raw-aio.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

stubs/linux-aio.c

+1 −1
Original line number Diff line number Diff line
@@ -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();

}