From 3c87ef6efb40f0e339d705c194b2224f854ec38e Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 3 Jun 2015 16:14:25 -0400 Subject: [PATCH] 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 --- fs/nfs/file.c | 15 ++------ include/linux/sunrpc/clnt.h | 1 + include/linux/sunrpc/sched.h | 16 +++++++++ net/sunrpc/clnt.c | 67 +++++++++++++++++++++++++++++++----- net/sunrpc/xprtsock.c | 3 +- 5 files changed, 78 insertions(+), 24 deletions(-) diff --git a/fs/nfs/file.c b/fs/nfs/file.c index 8b8d83a526ce..cc4fa1ed61fc 100644 --- a/fs/nfs/file.c +++ b/fs/nfs/file.c @@ -555,31 +555,22 @@ static int nfs_launder_page(struct page *page) return nfs_wb_page(inode, page); } -#ifdef CONFIG_NFS_SWAP static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file, sector_t *span) { - int ret; struct rpc_clnt *clnt = NFS_CLIENT(file->f_mapping->host); *span = sis->pages; - rcu_read_lock(); - ret = xs_swapper(rcu_dereference(clnt->cl_xprt), 1); - rcu_read_unlock(); - - return ret; + return rpc_clnt_swap_activate(clnt); } static void nfs_swap_deactivate(struct file *file) { struct rpc_clnt *clnt = NFS_CLIENT(file->f_mapping->host); - rcu_read_lock(); - xs_swapper(rcu_dereference(clnt->cl_xprt), 0); - rcu_read_unlock(); + rpc_clnt_swap_deactivate(clnt); } -#endif const struct address_space_operations nfs_file_aops = { .readpage = nfs_readpage, @@ -596,10 +587,8 @@ const struct address_space_operations nfs_file_aops = { .launder_page = nfs_launder_page, .is_dirty_writeback = nfs_check_dirty_writeback, .error_remove_page = generic_error_remove_page, -#ifdef CONFIG_NFS_SWAP .swap_activate = nfs_swap_activate, .swap_deactivate = nfs_swap_deactivate, -#endif }; /* diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h index 598ba80ec30c..131032f15cc1 100644 --- a/include/linux/sunrpc/clnt.h +++ b/include/linux/sunrpc/clnt.h @@ -56,6 +56,7 @@ struct rpc_clnt { struct rpc_rtt * cl_rtt; /* RTO estimator data */ const struct rpc_timeout *cl_timeout; /* Timeout strategy */ + atomic_t cl_swapper; /* swapfile count */ int cl_nodelen; /* nodename length */ char cl_nodename[UNX_MAXNODENAME+1]; struct rpc_pipe_dir_head cl_pipedir_objects; diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h index 2aa68976a482..d703f0ef37d8 100644 --- a/include/linux/sunrpc/sched.h +++ b/include/linux/sunrpc/sched.h @@ -268,4 +268,20 @@ static inline void rpc_assign_waitqueue_name(struct rpc_wait_queue *q, } #endif +#if IS_ENABLED(CONFIG_SUNRPC_SWAP) +int rpc_clnt_swap_activate(struct rpc_clnt *clnt); +void rpc_clnt_swap_deactivate(struct rpc_clnt *clnt); +#else +static inline int +rpc_clnt_swap_activate(struct rpc_clnt *clnt) +{ + return -EINVAL; +} + +static inline void +rpc_clnt_swap_deactivate(struct rpc_clnt *clnt) +{ +} +#endif /* CONFIG_SUNRPC_SWAP */ + #endif /* _LINUX_SUNRPC_SCHED_H_ */ 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) { -- 2.39.2