| Message ID | 1416839379-19677-3-git-send-email-ming.lei@canonical.com |
|---|---|
| State | New |
| Headers | show |
On Mon, Nov 24, 2014 at 10:29:38PM +0800, Ming Lei wrote: > Previously -EAGAIN is simply ignored for !s->io_q.plugged case, > and sometimes it is easy to cause -EIO to VM, such as NVME device. > > This patch handles -EAGAIN by io queue for !s->io_q.plugged case, > and it will be retried in following aio completion cb. > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Ming Lei <ming.lei@canonical.com> > --- > block/linux-aio.c | 28 ++++++++++++++++++---------- > 1 file changed, 18 insertions(+), 10 deletions(-) > > diff --git a/block/linux-aio.c b/block/linux-aio.c > index 70312a4..0cb098d 100644 > --- a/block/linux-aio.c > +++ b/block/linux-aio.c > @@ -282,12 +282,17 @@ static int ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb) > s->io_q.iocbs[idx++] = iocb; > s->io_q.idx = idx; > > - /* submit immediately if queue depth is above 2/3 */ > - if (idx > s->io_q.size * 2 / 3) { > - return ioq_submit(s); > + /* > + * This is reached in two cases: queue not plugged but io_submit > + * returned -EAGAIN, or queue plugged. In the latter case, start > + * submitting some I/O if the queue is getting too full. In the > + * former case, instead, wait until an I/O operation is completed. > + */ > + if (!s->io_q.plugged || likely(idx < s->io_q.size * 2 / 3)) { > + return 0; > } > > - return 0; > + return ioq_submit(s); Same as in the previous patch, the ioq_submit() return value is not meaningful to ioq_enqueue() callers. It should not be returned.
diff --git a/block/linux-aio.c b/block/linux-aio.c index 70312a4..0cb098d 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -282,12 +282,17 @@ static int ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb) s->io_q.iocbs[idx++] = iocb; s->io_q.idx = idx; - /* submit immediately if queue depth is above 2/3 */ - if (idx > s->io_q.size * 2 / 3) { - return ioq_submit(s); + /* + * This is reached in two cases: queue not plugged but io_submit + * returned -EAGAIN, or queue plugged. In the latter case, start + * submitting some I/O if the queue is getting too full. In the + * former case, instead, wait until an I/O operation is completed. + */ + if (!s->io_q.plugged || likely(idx < s->io_q.size * 2 / 3)) { + return 0; } - return 0; + return ioq_submit(s); } void laio_io_plug(BlockDriverState *bs, void *aio_ctx) @@ -348,15 +353,18 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd, } io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e)); - if (!s->io_q.plugged) { - if (io_submit(s->ctx, 1, &iocbs) < 0) { - goto out_free_aiocb; - } - } else { - if (ioq_enqueue(s, iocbs) < 0) { + /* Switch to queue mode until -EAGAIN is handled */ + if (!s->io_q.plugged && !s->io_q.idx) { + int ret = io_submit(s->ctx, 1, &iocbs); + if (ret >= 0) { + return &laiocb->common; + } else if (ret != -EAGAIN) { goto out_free_aiocb; } } + if (ioq_enqueue(s, iocbs) < 0) { + goto out_free_aiocb; + } return &laiocb->common; out_free_aiocb:
Previously -EAGAIN is simply ignored for !s->io_q.plugged case, and sometimes it is easy to cause -EIO to VM, such as NVME device. This patch handles -EAGAIN by io queue for !s->io_q.plugged case, and it will be retried in following aio completion cb. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Ming Lei <ming.lei@canonical.com> --- block/linux-aio.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-)