Re: [Xen-devel] [RFC Patch v3 04/18] blktap2: dynamic allocate aio_requests to avoid -EBUSY error

[Shriram Rajagopalan <rshriram@xxxxxxxxx>]

On Sep 5, 2014 5:13 AM, "Wen Congyang" <wency@xxxxxxxxxxxxxx> wrote:
>
> From: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
>
> In normal case, there are at most TAPDISK_DATA_REQUESTS request
> at the same time. But in remus mode, the write requests are
> forwarded from the master side, and cached in block-remus. All
> cached requests will be forwarded to aio driver when syncing
> primary vm and backup vm. In this case, The number of requests
> may be more than TAPDISK_DATA_REQUESTS. So aio driver can't hanlde
> these requests at the same time, it will cause tapdisk2 exit.
>
> We don't know how many requests will be handled, so dynamic allocate
> aio_requests to avoid this error.
>
> Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> Signed-off-by: Jiang Yunhong <yunhong.jiang@xxxxxxxxx>
> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
> Cc: Shriram Rajagopalan <rshriram@xxxxxxxxx>
> ---
> Âtools/blktap2/drivers/block-aio.c | 36 +++++++++++++++++++++++++++++++++---
> Â1 file changed, 33 insertions(+), 3 deletions(-)
>
> diff --git a/tools/blktap2/drivers/block-aio.c b/tools/blktap2/drivers/block-aio.c
> index f398da2..10ab20b 100644
> --- a/tools/blktap2/drivers/block-aio.c
> +++ b/tools/blktap2/drivers/block-aio.c
> @@ -55,9 +55,10 @@ struct tdaio_state {
>     int         fd;
>     td_driver_t    Â*driver;
>
> +   Âint         aio_max_count;
>     int         aio_free_count;
>     struct aio_request Âaio_requests[MAX_AIO_REQS];
> -   Âstruct aio_request *aio_free_list[MAX_AIO_REQS];
> +   Âstruct aio_request Â**aio_free_list;
> Â};
>
> Â/*Get Image size, secsize*/
> @@ -122,6 +123,11 @@ int tdaio_open(td_driver_t *driver, const char *name, td_flag_t flags)
>
> Â Â Â Â memset(prv, 0, sizeof(struct tdaio_state));
>
> +Â Â Â Âprv->aio_free_list = malloc(MAX_AIO_REQS * sizeof(*prv->aio_free_list));
> +Â Â Â Âif (!prv->aio_free_list)
> +Â Â Â Â Â Â Â Âreturn -ENOMEM;
> +
> +Â Â Â Âprv->aio_max_count = MAX_AIO_REQS;
> Â Â Â Â prv->aio_free_count = MAX_AIO_REQS;
> Â Â Â Â for (i = 0; i < MAX_AIO_REQS; i++)
> Â Â Â Â Â Â Â Â prv->aio_free_list[i] = &prv->aio_requests[i];
> @@ -159,6 +165,28 @@ done:
> Â Â Â Â return ret;
> Â}
>
> +static int tdaio_refill(struct tdaio_state *prv)
> +{
> +Â Â Â Âstruct aio_request **new, *new_req;
> +Â Â Â Âint i, max = prv->aio_max_count + MAX_AIO_REQS;
> +
> +Â Â Â Ânew = realloc(prv->aio_free_list, max * sizeof(*prv->aio_free_list));
> +Â Â Â Âif (!new)
> +Â Â Â Â Â Â Â Âreturn -1;
> +Â Â Â Âprv->aio_free_list = new;
> +
> +Â Â Â Ânew_req = calloc(MAX_AIO_REQS, sizeof(*new_req));
> +Â Â Â Âif (!new_req)
> +Â Â Â Â Â Â Â Âreturn -1;
> +
> +Â Â Â Âprv->aio_max_count = max;
> +Â Â Â Âprv->aio_free_count = MAX_AIO_REQS;
> +Â Â Â Âfor (i = 0; i < MAX_AIO_REQS; i++)
> +Â Â Â Â Â Â Â Âprv->aio_free_list[i] = &new_req[i];
> +
> +Â Â Â Âreturn 0;
> +}
> +
> Âvoid tdaio_complete(void *arg, struct tiocb *tiocb, int err)
> Â{
> Â Â Â Â struct aio_request *aio = (struct aio_request *)arg;
> @@ -207,8 +235,10 @@ void tdaio_queue_write(td_driver_t *driver, td_request_t treq)
>     size  = treq.secs * driver->info.sector_size;
>     offset = treq.sec * (uint64_t)driver->info.sector_size;
>
> -Â Â Â Âif (prv->aio_free_count == 0)
> -Â Â Â Â Â Â Â Âgoto fail;
> +Â Â Â Âif (prv->aio_free_count == 0) {
> +Â Â Â Â Â Â Â Âif (tdaio_refill(prv) < 0)
> +Â Â Â Â Â Â Â Â Â Â Â Âgoto fail;
> +Â Â Â Â}
>
>     aio    = prv->aio_free_list[--prv->aio_free_count];
>     aio->treq = treq;
> --
> 1.9.3
>

Hi
Sorry for the delay. The patch looks good to me.

Acked-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>

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