From: "J. Bruce Fields" <bfields@redhat.com>
Date: Tue, 19 Sep 2017 19:25:41 -0400
Subject: [PATCH] nfsd: give out fewer session slots as limit approaches
Git-commit: de766e570413bd0484af0b580299b495ada625c3
Patch-mainline: v4.15
References: bsc#1150381

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>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfsd/nfs4state.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1507,6 +1507,11 @@ static u32 nfsd4_get_drc_mem(struct nfsd
 	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);