cifs: prevent starvation in wait_for_free_credits for multi-credit requests
authorRonnie Sahlberg <lsahlber@redhat.com>
Fri, 8 Mar 2019 02:58:21 +0000 (12:58 +1000)
committerSteve French <stfrench@microsoft.com>
Fri, 15 Mar 2019 00:32:35 +0000 (19:32 -0500)
commit16b34aa44b257155d9392a19e08e4ce139bc2789
treea82a838ff7d699fe399913d393e9544b51b25c29
parentb227d215deef4f3528b8f754accef4db03539a59
cifs: prevent starvation in wait_for_free_credits for multi-credit requests

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.

However, we need to protect from servers that are very slow to hand out
new credits on new sessions so we only do this IFF there are 2*MAX_COMPOUND
(arbitrary) credits already in flight.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
fs/cifs/transport.c