The Friday 05 Sep 2014 à 00:27:07 (+0800), Ming Lei wrote :
> In the enqueue path, we can't complete request, otherwise
> "Co-routine re-entered recursively" may be caused, so this
> patch fixes the issue with the following ideas:
>
> - for -EAGAIN or partial completion, retry the submission by
> scheduling a BH in following completion cb
> - for part of completion, also update the io queue
> - for other failure, return the failure if in enqueue path,
> otherwise, abort all queued I/O
>
> Signed-off-by: Ming Lei <ming....@canonical.com>
> ---
> block/linux-aio.c | 106
> ++++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 81 insertions(+), 25 deletions(-)
>
> diff --git a/block/linux-aio.c b/block/linux-aio.c
> index 9aca758..a06576d 100644
> --- a/block/linux-aio.c
> +++ b/block/linux-aio.c
> @@ -38,11 +38,19 @@ struct qemu_laiocb {
> QLIST_ENTRY(qemu_laiocb) node;
> };
>
> -typedef struct {
> +/*
> + * TODO: support to batch I/O from multiple bs in one same
> + * AIO context, one important use case is multi-lun scsi,
> + * so in future the IO queue should be per AIO context.
> + */
> +typedef struct LaioQueue {
> struct iocb *iocbs[MAX_QUEUED_IO];
> int plugged;
> - unsigned int size;
> - unsigned int idx;
> + uint32 size;
> + uint32 idx;
Sorry Ming I said crap about struct, size and idx.
I initially misread that you where adding this.
You where right from the start.
> +
> + /* handle -EAGAIN and partial completion */
> + QEMUBH *retry;
> } LaioQueue;
>
> struct qemu_laio_state {
> @@ -138,6 +146,13 @@ static void qemu_laio_completion_bh(void *opaque)
> }
> }
>
> +static void qemu_laio_start_retry(struct qemu_laio_state *s)
> +{
> + if (s->io_q.idx) {
> + qemu_bh_schedule(s->io_q.retry);
> + }
> +}
> +
> static void qemu_laio_completion_cb(EventNotifier *e)
> {
> struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e);
> @@ -145,6 +160,7 @@ static void qemu_laio_completion_cb(EventNotifier *e)
> if (event_notifier_test_and_clear(&s->e)) {
> qemu_bh_schedule(s->completion_bh);
> }
> + qemu_laio_start_retry(s);
> }
>
> static void laio_cancel(BlockDriverAIOCB *blockacb)
> @@ -164,6 +180,7 @@ static void laio_cancel(BlockDriverAIOCB *blockacb)
> ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event);
> if (ret == 0) {
> laiocb->ret = -ECANCELED;
> + qemu_laio_start_retry(laiocb->ctx);
> return;
> }
>
> @@ -191,45 +208,80 @@ static void ioq_init(LaioQueue *io_q)
> io_q->plugged = 0;
> }
>
> -static int ioq_submit(struct qemu_laio_state *s)
> +static void abort_queue(struct qemu_laio_state *s)
> +{
> + int i;
> + for (i = 0; i < s->io_q.idx; i++) {
> + struct qemu_laiocb *laiocb = container_of(s->io_q.iocbs[i],
> + struct qemu_laiocb,
> + iocb);
> + laiocb->ret = -EIO;
> + qemu_laio_process_completion(s, laiocb);
> + }
> +}
> +
> +static int ioq_submit(struct qemu_laio_state *s, bool enqueue)
> {
> int ret, i = 0;
> int len = s->io_q.idx;
> + int j = 0;
>
> - do {
> - ret = io_submit(s->ctx, len, s->io_q.iocbs);
> - } while (i++ < 3 && ret == -EAGAIN);
> + if (!len) {
> + return 0;
> + }
>
> - /* empty io queue */
> - s->io_q.idx = 0;
> + ret = io_submit(s->ctx, len, s->io_q.iocbs);
> + if (ret == -EAGAIN) { /* retry in following completion cb */
> + return 0;
> + } else if (ret < 0) {
> + if (enqueue) {
> + return ret;
> + }
>
> - if (ret < 0) {
> - i = 0;
> - } else {
> - i = ret;
> + /* in non-queue path, all IOs have to be completed */
> + abort_queue(s);
> + ret = len;
> + } else if (ret == 0) {
> + goto out;
> }
>
> - for (; i < len; i++) {
> - struct qemu_laiocb *laiocb =
> - container_of(s->io_q.iocbs[i], struct qemu_laiocb, iocb);
> -
> - laiocb->ret = (ret < 0) ? ret : -EIO;
> - qemu_laio_process_completion(s, laiocb);
> + for (i = ret; i < len; i++) {
> + s->io_q.iocbs[j++] = s->io_q.iocbs[i];
> }
> +
> + out:
> + /*
> + * update io queue, for partial completion, retry will be
> + * started automatically in following completion cb.
> + */
> + s->io_q.idx -= ret;
> +
> return ret;
> }
>
> -static void ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
> +static void ioq_submit_retry(void *opaque)
> +{
> + struct qemu_laio_state *s = opaque;
> + ioq_submit(s, false);
> +}
> +
> +static int ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
> {
> unsigned int idx = s->io_q.idx;
>
> + if (unlikely(idx == s->io_q.size)) {
> + return -1;
> + }
> +
> s->io_q.iocbs[idx++] = iocb;
> s->io_q.idx = idx;
>
> - /* submit immediately if queue is full */
> - if (idx == s->io_q.size) {
> - ioq_submit(s);
> + /* submit immediately if queue depth is above 2/3 */
> + if (idx > s->io_q.size * 2 / 3) {
> + return ioq_submit(s, true);
> }
> +
> + return 0;
> }
>
> void laio_io_plug(BlockDriverState *bs, void *aio_ctx)
> @@ -251,7 +303,7 @@ int laio_io_unplug(BlockDriverState *bs, void *aio_ctx,
> bool unplug)
> }
>
> if (s->io_q.idx > 0) {
> - ret = ioq_submit(s);
> + ret = ioq_submit(s, false);
> }
>
> return ret;
> @@ -295,7 +347,9 @@ BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void
> *aio_ctx, int fd,
> goto out_free_aiocb;
> }
> } else {
> - ioq_enqueue(s, iocbs);
> + if (ioq_enqueue(s, iocbs) < 0) {
> + goto out_free_aiocb;
> + }
> }
> return &laiocb->common;
>
> @@ -310,12 +364,14 @@ void laio_detach_aio_context(void *s_, AioContext
> *old_context)
>
> aio_set_event_notifier(old_context, &s->e, NULL);
> qemu_bh_delete(s->completion_bh);
> + qemu_bh_delete(s->io_q.retry);
> }
>
> void laio_attach_aio_context(void *s_, AioContext *new_context)
> {
> struct qemu_laio_state *s = s_;
>
> + s->io_q.retry = aio_bh_new(new_context, ioq_submit_retry, s);
> s->completion_bh = aio_bh_new(new_context, qemu_laio_completion_bh, s);
> aio_set_event_notifier(new_context, &s->e, qemu_laio_completion_cb);
> }
> --
> 1.7.9.5
>
>
