[PATCH 4.4 103/158] nfsd: give out fewer session slots as limit approaches

Greg Kroah-Hartman
2019-08-02T09:34:03Z

[ Upstream commit de766e570413bd0484af0b580299b495ada625c3 ]

Instead of granting client's full requests until we hit our DRC size
limit and then failing CREATE_SESSIONs (and hence mounts) completely,
start granting clients smaller slot tables as we approach the limit.

The factor chosen here is pretty much arbitrary.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfsd/nfs4state.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index ba27a5ff8677..eb0f8af5203a 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1396,6 +1396,11 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca)
spin_lock(&nfsd_drc_lock);
avail = min((unsigned long)NFSD_MAX_MEM_PER_SESSION,
nfsd_drc_max_mem - nfsd_drc_mem_used);
+ /*
+ * Never use more than a third of the remaining memory,
+ * unless it's the only way to give this client a slot:
+ */
+ avail = clamp_t(int, avail, slotsize, avail/3);
num = min_t(int, num, avail / slotsize);
nfsd_drc_mem_used += num * slotsize;
spin_unlock(&nfsd_drc_lock);
--
2.20.1