Commit c487216b authored by NeilBrown's avatar NeilBrown Committed by Trond Myklebust

SUNRPC/call_alloc: async tasks mustn't block waiting for memory

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: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent 944d95f7
...@@ -1023,8 +1023,10 @@ int rpc_malloc(struct rpc_task *task) ...@@ -1023,8 +1023,10 @@ int rpc_malloc(struct rpc_task *task)
struct rpc_buffer *buf; struct rpc_buffer *buf;
gfp_t gfp = GFP_KERNEL; gfp_t gfp = GFP_KERNEL;
if (RPC_IS_ASYNC(task))
gfp = GFP_NOWAIT | __GFP_NOWARN;
if (RPC_IS_SWAPPER(task)) if (RPC_IS_SWAPPER(task))
gfp = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN; gfp |= __GFP_MEMALLOC;
size += sizeof(struct rpc_buffer); size += sizeof(struct rpc_buffer);
if (size <= RPC_BUFFER_MAXSIZE) if (size <= RPC_BUFFER_MAXSIZE)
......
...@@ -570,8 +570,10 @@ xprt_rdma_allocate(struct rpc_task *task) ...@@ -570,8 +570,10 @@ xprt_rdma_allocate(struct rpc_task *task)
gfp_t flags; gfp_t flags;
flags = RPCRDMA_DEF_GFP; flags = RPCRDMA_DEF_GFP;
if (RPC_IS_ASYNC(task))
flags = GFP_NOWAIT | __GFP_NOWARN;
if (RPC_IS_SWAPPER(task)) if (RPC_IS_SWAPPER(task))
flags = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN; flags |= __GFP_MEMALLOC;
if (!rpcrdma_check_regbuf(r_xprt, req->rl_sendbuf, rqst->rq_callsize, if (!rpcrdma_check_regbuf(r_xprt, req->rl_sendbuf, rqst->rq_callsize,
flags)) flags))
......
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