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Commit 28b4a8bc authored by Cheng Lin's avatar Cheng Lin Committed by Greg Kroah-Hartman
Browse files

nfs_common: need lock during iterate through the list 



[ 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: c87fb4a3 ("lockd: NLM grace period shouldn't block NFSv4 opens")
Signed-off-by: default avatar < Cheng Lin &lt;cheng.lin130@zte.com.cn>
Signed-off-by: default avatar < Yi Wang &lt;wang.yi59@zte.com.cn>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 4deb1c33

fs/nfs_common/grace.c

+5 −1
Original line number Diff line number Diff line
@@ -75,10 +75,14 @@ __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;

}