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authorJeff Layton <jlayton@poochiereds.net>2015-06-03 22:14:25 +0200
committerTrond Myklebust <trond.myklebust@primarydata.com>2015-06-11 00:26:14 +0200
commit3c87ef6efb40f0e339d705c194b2224f854ec38e (patch)
tree2878ea261637cf6c85ab69b9cbde70a036b1e3a2 /net
parentSUNRPC: Fix a backchannel race (diff)
downloadlinux-3c87ef6efb40f0e339d705c194b2224f854ec38e.tar.xz
linux-3c87ef6efb40f0e339d705c194b2224f854ec38e.zip
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 <mgorman@suse.de> Reported-by: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Jeff Layton <jeff.layton@primarydata.com> Reviewed-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'net')
-rw-r--r--net/sunrpc/clnt.c67
-rw-r--r--net/sunrpc/xprtsock.c3
2 files changed, 59 insertions, 11 deletions
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)
{