From 3c87ef6efb40f0e339d705c194b2224f854ec38e Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 3 Jun 2015 16:14:25 -0400 Subject: sunrpc: keep a count of swapfiles associated with the rpc_clnt Jerome reported seeing a warning pop when working with a swapfile on NFS. The nfs_swap_activate can end up calling sk_set_memalloc while holding the rcu_read_lock and that function can sleep. To fix that, we need to take a reference to the xprt while holding the rcu_read_lock, set the socket up for swapping and then drop that reference. But, xprt_put is not exported and having NFS deal with the underlying xprt is a bit of layering violation anyway. Fix this by adding a set of activate/deactivate functions that take a rpc_clnt pointer instead of an rpc_xprt, and have nfs_swap_activate and nfs_swap_deactivate call those. Also, add a per-rpc_clnt atomic counter to keep track of the number of active swapfiles associated with it. When the counter does a 0->1 transition, we enable swapping on the xprt, when we do a 1->0 transition we disable swapping on it. This also allows us to be a bit more selective with the RPC_TASK_SWAPPER flag. If non-swapper and swapper clnts are sharing a xprt, then we only need to flag the tasks from the swapper clnt with that flag. Acked-by: Mel Gorman Reported-by: Jerome Marchand Signed-off-by: Jeff Layton Reviewed-by: Chuck Lever Signed-off-by: Trond Myklebust --- net/sunrpc/clnt.c | 67 ++++++++++++++++++++++++++++++++++++++++++++------- net/sunrpc/xprtsock.c | 3 +-- 2 files changed, 59 insertions(+), 11 deletions(-) (limited to 'net/sunrpc') diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index f6717170480e..0ba65156a62b 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -891,15 +891,8 @@ void rpc_task_set_client(struct rpc_task *task, struct rpc_clnt *clnt) task->tk_flags |= RPC_TASK_SOFT; if (clnt->cl_noretranstimeo) task->tk_flags |= RPC_TASK_NO_RETRANS_TIMEOUT; - if (sk_memalloc_socks()) { - struct rpc_xprt *xprt; - - rcu_read_lock(); - xprt = rcu_dereference(clnt->cl_xprt); - if (xprt->swapper) - task->tk_flags |= RPC_TASK_SWAPPER; - rcu_read_unlock(); - } + if (atomic_read(&clnt->cl_swapper)) + task->tk_flags |= RPC_TASK_SWAPPER; /* Add to the client's list of all tasks */ spin_lock(&clnt->cl_lock); list_add_tail(&task->tk_task, &clnt->cl_tasks); @@ -2479,3 +2472,59 @@ void rpc_show_tasks(struct net *net) spin_unlock(&sn->rpc_client_lock); } #endif + +#if IS_ENABLED(CONFIG_SUNRPC_SWAP) +int +rpc_clnt_swap_activate(struct rpc_clnt *clnt) +{ + int ret = 0; + struct rpc_xprt *xprt; + + if (atomic_inc_return(&clnt->cl_swapper) == 1) { +retry: + rcu_read_lock(); + xprt = xprt_get(rcu_dereference(clnt->cl_xprt)); + rcu_read_unlock(); + if (!xprt) { + /* + * If we didn't get a reference, then we likely are + * racing with a migration event. Wait for a grace + * period and try again. + */ + synchronize_rcu(); + goto retry; + } + + ret = xs_swapper(xprt, 1); + xprt_put(xprt); + } + return ret; +} +EXPORT_SYMBOL_GPL(rpc_clnt_swap_activate); + +void +rpc_clnt_swap_deactivate(struct rpc_clnt *clnt) +{ + struct rpc_xprt *xprt; + + if (atomic_dec_if_positive(&clnt->cl_swapper) == 0) { +retry: + rcu_read_lock(); + xprt = xprt_get(rcu_dereference(clnt->cl_xprt)); + rcu_read_unlock(); + if (!xprt) { + /* + * If we didn't get a reference, then we likely are + * racing with a migration event. Wait for a grace + * period and try again. + */ + synchronize_rcu(); + goto retry; + } + + xs_swapper(xprt, 0); + xprt_put(xprt); + } +} +EXPORT_SYMBOL_GPL(rpc_clnt_swap_deactivate); +#endif /* CONFIG_SUNRPC_SWAP */ diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index b142feef0cf4..f344c0f8974c 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -1955,7 +1955,7 @@ static void xs_local_connect(struct rpc_xprt *xprt, struct rpc_task *task) msleep_interruptible(15000); } -#ifdef CONFIG_SUNRPC_SWAP +#if IS_ENABLED(CONFIG_SUNRPC_SWAP) static void xs_set_memalloc(struct rpc_xprt *xprt) { struct sock_xprt *transport = container_of(xprt, struct sock_xprt, @@ -1987,7 +1987,6 @@ int xs_swapper(struct rpc_xprt *xprt, int enable) return err; } -EXPORT_SYMBOL_GPL(xs_swapper); #else static void xs_set_memalloc(struct rpc_xprt *xprt) { -- cgit v1.2.3-59-g8ed1b