NFS client system hangs with heavy IO load, rpciod stuck at nfs_commit_inode often from socket memory allocation

Solution Verified - Updated -

Issue

  • Randomly seeing "blocked for more than 120 seconds" and stacktrace on NFS client systems, which seems to occur during periods of heavy IO load.
  • See nfs: server [...] not responding, still trying indicating NFS client is having difficulty receiving responses from the NFS server
  • vmore shows rpciod, which processes NFS RPC task completions, can end up stuck waiting for NFS operations to complete, in nfs_commit_inode, from a memory allocation path from xs_create_sock, similar to:
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]  <----------- waiting on NFS operations to complete
 #5 [ffff8810343bf4f8] nfs_release_page at ffffffffa038bef6 [nfs]  <----------- calling back into 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   <------------------------------- memory allocation
#19 [ffff8810343bfce8] inet_create at ffffffff81483ba6
#20 [ffff8810343bfd38] __sock_create at ffffffff8140b4a7
#21 [ffff8810343bfd98] xs_create_sock at ffffffffa01f649b [sunrpc]   <---------------------------- socket creation
#22 [ffff8810343bfdd8] xs_tcp_setup_socket at ffffffffa01f6965 [sunrpc]
#23 [ffff8810343bfe38] worker_thread at ffffffff810887d0

Environment

  • Red Hat Enterprise Linux 6.1 - 6.3
    • kernel 2.6.32-131.*el6 up to 2.6.32-279.*el6
  • Red Hat Enterprise Linux 5
    • seen on kernel 2.6.18-194.el5
    • all versions believed to be affected
  • NFS client

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