From 353b19562a03d5605b90abc2858c2b7d305527c1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Cheng=C2=A0Lin?= Date: Tue, 1 Dec 2020 07:06:35 -0500 Subject: [PATCH] nfs_common: need lock during iterate through the list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Upstream commit 4a9d81caf841cd2c0ae36abec9c2963bf21d0284 ] If the elem is deleted during be iterated on it, the iteration process will fall into an endless loop. kernel: NMI watchdog: BUG: soft lockup - CPU#4 stuck for 22s! [nfsd:17137] PID: 17137  TASK: ffff8818d93c0000  CPU: 4   COMMAND: "nfsd"     [exception RIP: __state_in_grace+76]     RIP: ffffffffc00e817c  RSP: ffff8818d3aefc98  RFLAGS: 00000246     RAX: ffff881dc0c38298  RBX: ffffffff81b03580  RCX: ffff881dc02c9f50     RDX: ffff881e3fce8500  RSI: 0000000000000001  RDI: ffffffff81b03580     RBP: ffff8818d3aefca0   R8: 0000000000000020   R9: ffff8818d3aefd40     R10: ffff88017fc03800  R11: ffff8818e83933c0  R12: ffff8818d3aefd40     R13: 0000000000000000  R14: ffff8818e8391068  R15: ffff8818fa6e4000     CS: 0010  SS: 0018  #0 [ffff8818d3aefc98] opens_in_grace at ffffffffc00e81e3 [grace]  #1 [ffff8818d3aefca8] nfs4_preprocess_stateid_op at ffffffffc02a3e6c [nfsd]  #2 [ffff8818d3aefd18] nfsd4_write at ffffffffc028ed5b [nfsd]  #3 [ffff8818d3aefd80] nfsd4_proc_compound at ffffffffc0290a0d [nfsd]  #4 [ffff8818d3aefdd0] nfsd_dispatch at ffffffffc027b800 [nfsd]  #5 [ffff8818d3aefe08] svc_process_common at ffffffffc02017f3 [sunrpc]  #6 [ffff8818d3aefe70] svc_process at ffffffffc0201ce3 [sunrpc]  #7 [ffff8818d3aefe98] nfsd at ffffffffc027b117 [nfsd]  #8 [ffff8818d3aefec8] kthread at ffffffff810b88c1  #9 [ffff8818d3aeff50] ret_from_fork at ffffffff816d1607 The troublemake elem: crash> lock_manager ffff881dc0c38298 struct lock_manager {   list = {     next = 0xffff881dc0c38298,     prev = 0xffff881dc0c38298   },   block_opens = false } Fixes: c87fb4a378f9 ("lockd: NLM grace period shouldn't block NFSv4 opens") Signed-off-by: Cheng Lin  Signed-off-by: Yi Wang  Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin --- fs/nfs_common/grace.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c index b73d9dd37f73..26f2a50eceac 100644 --- a/fs/nfs_common/grace.c +++ b/fs/nfs_common/grace.c @@ -69,10 +69,14 @@ __state_in_grace(struct net *net, bool open) if (!open) return !list_empty(grace_list); + spin_lock(&grace_lock); list_for_each_entry(lm, grace_list, list) { - if (lm->block_opens) + if (lm->block_opens) { + spin_unlock(&grace_lock); return true; + } } + spin_unlock(&grace_lock); return false; }