diff mbox series

[4.19,293/338] SUNRPC/call_alloc: async tasks mustnt block waiting for memory

Message ID 20220414110847.227926095@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH April 14, 2022, 1:13 p.m. UTC 
From: NeilBrown <neilb@suse.de>

[ 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 <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sunrpc/sched.c              | 4 +++-
 net/sunrpc/xprtrdma/transport.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index e339f8da1b0a..e36ae4d4b540 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -893,8 +893,10 @@  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 fdd14908eacb..e87a79be7ef0 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -665,8 +665,10 @@  xprt_rdma_allocate(struct rpc_task *task)
 	gfp_t flags;
 
 	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_sendbuf(r_xprt, req, rqst->rq_callsize, flags))
 		goto out_fail;