nfs: skip commit in releasepage if we're freeing memory for fs-related reasons

commit 5cf02d09b50b1ee1c2d536c9cf64af5a7d433f56 upstream.

We've had some reports of a deadlock where rpciod ends up with a stack
trace like this:

    PID: 2507   TASK: ffff88103691ab40  CPU: 14  COMMAND: "rpciod/14"
     #0 [ffff8810343bf2f0] schedule at ffffffff814dabd9
     #1 [ffff8810343bf3b8] nfs_wait_bit_killable at ffffffffa038fc04 [nfs]
     #2 [ffff8810343bf3c8] __wait_on_bit at ffffffff814dbc2f
     #3 [ffff8810343bf418] out_of_line_wait_on_bit at ffffffff814dbcd8
     #4 [ffff8810343bf488] nfs_commit_inode at ffffffffa039e0c1 [nfs]
     #5 [ffff8810343bf4f8] nfs_release_page at ffffffffa038bef6 [nfs]
     #6 [ffff8810343bf528] try_to_release_page at ffffffff8110c670
     #7 [ffff8810343bf538] shrink_page_list.clone.0 at ffffffff81126271
     #8 [ffff8810343bf668] shrink_inactive_list at ffffffff81126638
     #9 [ffff8810343bf818] shrink_zone at ffffffff8112788f
    #10 [ffff8810343bf8c8] do_try_to_free_pages at ffffffff81127b1e
    #11 [ffff8810343bf958] try_to_free_pages at ffffffff8112812f
    #12 [ffff8810343bfa08] __alloc_pages_nodemask at ffffffff8111fdad
    #13 [ffff8810343bfb28] kmem_getpages at ffffffff81159942
    #14 [ffff8810343bfb58] fallback_alloc at ffffffff8115a55a
    #15 [ffff8810343bfbd8] ____cache_alloc_node at ffffffff8115a2d9
    #16 [ffff8810343bfc38] kmem_cache_alloc at ffffffff8115b09b
    #17 [ffff8810343bfc78] sk_prot_alloc at ffffffff81411808
    #18 [ffff8810343bfcb8] sk_alloc at ffffffff8141197c
    #19 [ffff8810343bfce8] inet_create at ffffffff81483ba6
    #20 [ffff8810343bfd38] __sock_create at ffffffff8140b4a7
    #21 [ffff8810343bfd98] xs_create_sock at ffffffffa01f649b [sunrpc]
    #22 [ffff8810343bfdd8] xs_tcp_setup_socket at ffffffffa01f6965 [sunrpc]
    #23 [ffff8810343bfe38] worker_thread at ffffffff810887d0
    #24 [ffff8810343bfee8] kthread at ffffffff8108dd96
    #25 [ffff8810343bff48] kernel_thread at ffffffff8100c1ca

rpciod is trying to allocate memory for a new socket to talk to the
server. The VM ends up calling ->releasepage to get more memory, and it
tries to do a blocking commit. That commit can't succeed however without
a connected socket, so we deadlock.

Fix this by setting PF_FSTRANS on the workqueue task prior to doing the
socket allocation, and having nfs_release_page check for that flag when
deciding whether to do a commit call. Also, set PF_FSTRANS
unconditionally in rpc_async_schedule since that function can also do
allocations sometimes.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index c43a452..961e562 100644 (file)
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -452,8 +452,11 @@ static int nfs_release_page(struct page *page, gfp_t gfp)
 
        dfprintk(PAGECACHE, "NFS: release_page(%p)\n", page);
 
-       /* Only do I/O if gfp is a superset of GFP_KERNEL */
-       if (mapping && (gfp & GFP_KERNEL) == GFP_KERNEL) {
+       /* Only do I/O if gfp is a superset of GFP_KERNEL, and we're not
+        * doing this memory reclaim for a fs-related allocation.
+        */
+       if (mapping && (gfp & GFP_KERNEL) == GFP_KERNEL &&
+           !(current->flags & PF_FSTRANS)) {
                int how = FLUSH_SYNC;
 
                /* Don't let kswapd deadlock waiting for OOM RPC calls */

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 4e2b3b4..c90b832 100644 (file)
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -755,7 +755,9 @@ void rpc_execute(struct rpc_task *task)
 
 static void rpc_async_schedule(struct work_struct *work)
 {
+       current->flags |= PF_FSTRANS;
        __rpc_execute(container_of(work, struct rpc_task, u.tk_work));
+       current->flags &= ~PF_FSTRANS;
 }
 
 /**

diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index b446e10..06cdbff 100644 (file)
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -200,6 +200,7 @@ xprt_rdma_connect_worker(struct work_struct *work)
        int rc = 0;
 
        if (!xprt->shutdown) {
+               current->flags |= PF_FSTRANS;
                xprt_clear_connected(xprt);
 
                dprintk("RPC:       %s: %sconnect\n", __func__,
@@ -212,10 +213,10 @@ xprt_rdma_connect_worker(struct work_struct *work)
 
 out:
        xprt_wake_pending_tasks(xprt, rc);
-
 out_clear:
        dprintk("RPC:       %s: exit\n", __func__);
        xprt_clear_connecting(xprt);
+       current->flags &= ~PF_FSTRANS;
 }
 
 /*

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 55472c4..1a6edc7 100644 (file)
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1895,6 +1895,8 @@ static void xs_local_setup_socket(struct work_struct *work)
        if (xprt->shutdown)
                goto out;
 
+       current->flags |= PF_FSTRANS;
+
        clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);
        status = __sock_create(xprt->xprt_net, AF_LOCAL,
                                        SOCK_STREAM, 0, &sock, 1);
@@ -1928,6 +1930,7 @@ static void xs_local_setup_socket(struct work_struct *work)
 out:
        xprt_clear_connecting(xprt);
        xprt_wake_pending_tasks(xprt, status);
+       current->flags &= ~PF_FSTRANS;
 }
 
 static void xs_udp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
@@ -1970,6 +1973,8 @@ static void xs_udp_setup_socket(struct work_struct *work)
        if (xprt->shutdown)
                goto out;
 
+       current->flags |= PF_FSTRANS;
+
        /* Start by resetting any existing state */
        xs_reset_transport(transport);
        sock = xs_create_sock(xprt, transport,
@@ -1988,6 +1993,7 @@ static void xs_udp_setup_socket(struct work_struct *work)
 out:
        xprt_clear_connecting(xprt);
        xprt_wake_pending_tasks(xprt, status);
+       current->flags &= ~PF_FSTRANS;
 }
 
 /*
@@ -2113,6 +2119,8 @@ static void xs_tcp_setup_socket(struct work_struct *work)
        if (xprt->shutdown)
                goto out;
 
+       current->flags |= PF_FSTRANS;
+
        if (!sock) {
                clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);
                sock = xs_create_sock(xprt, transport,
@@ -2162,6 +2170,7 @@ static void xs_tcp_setup_socket(struct work_struct *work)
        case -EINPROGRESS:
        case -EALREADY:
                xprt_clear_connecting(xprt);
+               current->flags &= ~PF_FSTRANS;
                return;
        case -EINVAL:
                /* Happens, for instance, if the user specified a link
@@ -2174,6 +2183,7 @@ out_eagain:
 out:
        xprt_clear_connecting(xprt);
        xprt_wake_pending_tasks(xprt, status);
+       current->flags &= ~PF_FSTRANS;
 }
 
 /**