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From:   Roberto Bergantinos Corpas <rbergant@redhat.com>
To:     bfields@fieldses.org
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH] sunrpc: raise kernel RPC channel buffer size
Date:   Mon, 19 Oct 2020 11:33:56 +0200
Message-Id: <20201019093356.7395-1-rbergant@redhat.com>
MIME-Version: 1.0
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Its possible that using AUTH_SYS and mountd manage-gids option a
user may hit the 8k RPC channel buffer limit. This have been observed
on field, causing unanswered RPCs on clients after mountd fails to
write on channel :

rpc.mountd[11231]: auth_unix_gid: error writing reply

Userland nfs-utils uses a buffer size of 32k (RPC_CHAN_BUF_SIZE), so
lets match those two.

Signed-off-by: Roberto Bergantinos Corpas <rbergant@redhat.com>
---
 net/sunrpc/cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index baef5ee43dbb..08df4c599ab3 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -908,7 +908,7 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
 static ssize_t cache_slow_downcall(const char __user *buf,
 				   size_t count, struct cache_detail *cd)
 {
-	static char write_buf[8192]; /* protected by queue_io_mutex */
+	static char write_buf[32768]; /* protected by queue_io_mutex */
 	ssize_t ret = -EINVAL;
 
 	if (count >= sizeof(write_buf))
-- 
2.21.0