ср, 27 февр. 2019 г. в 22:26, Ronnie Sahlberg <lsahlber@xxxxxxxxxx>:
>
> Reserve the last MAX_COMPOUND credits for any request asking for >1 credit.
> This is to prevent future compound requests from becoming starved while waiting
> for potentially many requests is there is a large number of concurrent
> singe-credit requests.
>
> Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
> ---
> fs/cifs/transport.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index baf15194aa3d..4ff832fce2e9 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -520,6 +520,29 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
> }
>
> /*
> + * For normal commands, reserve the last MAX_COMPOUND
> + * credits to compound requests.
> + * Otherwise these compounds could be permanently
> + * starved for credits by single-credit requests.
> + *
> + * To prevent spinning CPU, block this thread until
> + * there are >MAX_COMPOUND credits available.
> + */
> + if (!optype && num_credits == 1 &&
What if server decides to grants us credits gradually? E.g. granted
only 2 during negotiate protocol and session setup. The tree connect
will wait forever here.
> + *credits <= MAX_COMPOUND) {
> + spin_unlock(&server->req_lock);
> + cifs_num_waiters_inc(server);
> + rc = wait_event_killable(server->request_q,
> + has_credits(server, credits,
> + MAX_COMPOUND + 1));
> + cifs_num_waiters_dec(server);
> + if (rc)
> + return rc;
> + spin_lock(&server->req_lock);
> + continue;
> + }
> +
> + /*
> * Can not count locking commands against total
> * as they are allowed to block on server.
> */
> --
> 2.13.6
>
--
Best regards,
Pavel Shilovsky
