linux-kernel - [PATCH 4.9 156/223] nfsd: give out fewer session slots as limit approaches

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Message-Id: <20190802092248.438219254@linuxfoundation.org>
Date:   Fri,  2 Aug 2019 11:36:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "J. Bruce Fields" <bfields@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 156/223] nfsd: give out fewer session slots as limit approaches

[ 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@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/nfsd/nfs4state.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 3656f87d11e3..0aacd1c850c3 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1507,6 +1507,11 @@ 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