From cec05d9901581c7bb4fa710cb145fa4ffe6a4eab Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 7 Mar 2022 10:41:44 +1100 Subject: [PATCH] SUNRPC/call_alloc: async tasks mustn't block waiting for memory [ Upstream commit c487216bec83b0c5a8803e5c61433d33ad7b104d ] When memory is short, new worker threads cannot be created and we depend on the minimum one rpciod thread to be able to handle everything. So it must not block waiting for memory. mempools are particularly a problem as memory can only be released back to the mempool by an async rpc task running. If all available workqueue threads are waiting on the mempool, no thread is available to return anything. rpc_malloc() can block, and this might cause deadlocks. So check RPC_IS_ASYNC(), rather than RPC_IS_SWAPPER() to determine if blocking is acceptable. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- net/sunrpc/sched.c | 4 +++- net/sunrpc/xprtrdma/transport.c | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index 00d95fefdc6fd..ccb9fa5812d8a 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -883,8 +883,10 @@ int rpc_malloc(struct rpc_task *task) struct rpc_buffer *buf; gfp_t gfp = GFP_NOIO | __GFP_NOWARN; + if (RPC_IS_ASYNC(task)) + gfp = GFP_NOWAIT | __GFP_NOWARN; if (RPC_IS_SWAPPER(task)) - gfp = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN; + gfp |= __GFP_MEMALLOC; size += sizeof(struct rpc_buffer); if (size <= RPC_BUFFER_MAXSIZE) diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c index 3ea3bb64b6d5c..f308f286e9aa4 100644 --- a/net/sunrpc/xprtrdma/transport.c +++ b/net/sunrpc/xprtrdma/transport.c @@ -577,8 +577,10 @@ xprt_rdma_allocate(struct rpc_task *task) return -ENOMEM; flags = RPCRDMA_DEF_GFP; + if (RPC_IS_ASYNC(task)) + flags = GFP_NOWAIT | __GFP_NOWARN; if (RPC_IS_SWAPPER(task)) - flags = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN; + flags |= __GFP_MEMALLOC; if (!rpcrdma_get_rdmabuf(r_xprt, req, flags)) goto out_fail; -- 2.47.3