@@ -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,
@@ -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;
}
@@ -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);
@@ -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);
@@ -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();
}
@@ -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)
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> --- Test case 1: Set /proc/sys/fs/max-aio-nr to 0. Start a guest with an aio=native disk. Result: laio_init() returns NULL due to not being able to allocate any AIO contexts. This NULL is assigned to ctx->linux_aio and dereferenced in aio_get_linux_aio. Test case 2: Set /proc/sys/fs/max-aio-nr to 128. Start a guest with an aio=native disk and one in-use I/O thread. Result: laio_init() returns NULL due to not being able to allocate additional AIO contexts for the I/O thread. This NULL is assigned to ctx->linux_aio and dereferenced in aio_get_linux_aio. Changes from v3 -> v4 (thanks to Fam Zheng and Kevin Wolf for review): Squash patch 2/2 into 1/2. Differentiate the possible reasons for laio_init() failing and use an Error ** to propagate the errno to the caller. Changes from v2 -> v3 (thanks to Eric Blake and Kevin Wolf for review): Use a boolean false rather than 0 in assignment to use_linux_aio. Drop ending '.' from error_report() calls. Fix typo in commit message (propogates -> propagates). Move aio_setup_linux_aio call to raw_open_common. Changes from v1 -> v2 (thanks to Kevin Wolf for review): Rather than affect virtio-scsi/blk at all, make all the changes internal to file-posix.c. Thanks to Kevin Wolf for the suggested change. block/file-posix.c | 33 ++++++++++++++++++++++++++++----- block/linux-aio.c | 12 +++++++++--- include/block/aio.h | 3 +++ include/block/raw-aio.h | 2 +- stubs/linux-aio.c | 2 +- util/async.c | 14 +++++++++++--- 6 files changed, 53 insertions(+), 13 deletions(-)