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![Cheng Lin](/assets/img/avatar_default.png)
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: c87fb4a378
("lockd: NLM grace period shouldn't block NFSv4 opens")
Signed-off-by: Cheng Lin <cheng.lin130@zte.com.cn>
Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
143 lines
3.4 KiB
C
143 lines
3.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Common code for control of lockd and nfsv4 grace periods.
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*
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* Transplanted from lockd code
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*/
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#include <linux/module.h>
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#include <net/net_namespace.h>
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#include <net/netns/generic.h>
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#include <linux/fs.h>
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static unsigned int grace_net_id;
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static DEFINE_SPINLOCK(grace_lock);
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/**
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* locks_start_grace
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* @net: net namespace that this lock manager belongs to
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* @lm: who this grace period is for
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*
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* A grace period is a period during which locks should not be given
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* out. Currently grace periods are only enforced by the two lock
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* managers (lockd and nfsd), using the locks_in_grace() function to
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* check when they are in a grace period.
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*
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* This function is called to start a grace period.
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*/
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void
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locks_start_grace(struct net *net, struct lock_manager *lm)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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spin_lock(&grace_lock);
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if (list_empty(&lm->list))
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list_add(&lm->list, grace_list);
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else
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WARN(1, "double list_add attempt detected in net %x %s\n",
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net->ns.inum, (net == &init_net) ? "(init_net)" : "");
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spin_unlock(&grace_lock);
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}
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EXPORT_SYMBOL_GPL(locks_start_grace);
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/**
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* locks_end_grace
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* @net: net namespace that this lock manager belongs to
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* @lm: who this grace period is for
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*
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* Call this function to state that the given lock manager is ready to
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* resume regular locking. The grace period will not end until all lock
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* managers that called locks_start_grace() also call locks_end_grace().
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* Note that callers count on it being safe to call this more than once,
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* and the second call should be a no-op.
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*/
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void
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locks_end_grace(struct lock_manager *lm)
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{
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spin_lock(&grace_lock);
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list_del_init(&lm->list);
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spin_unlock(&grace_lock);
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}
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EXPORT_SYMBOL_GPL(locks_end_grace);
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static bool
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__state_in_grace(struct net *net, bool open)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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struct lock_manager *lm;
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if (!open)
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return !list_empty(grace_list);
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spin_lock(&grace_lock);
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list_for_each_entry(lm, grace_list, list) {
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if (lm->block_opens) {
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spin_unlock(&grace_lock);
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return true;
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}
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}
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spin_unlock(&grace_lock);
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return false;
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}
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/**
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* locks_in_grace
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*
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* Lock managers call this function to determine when it is OK for them
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* to answer ordinary lock requests, and when they should accept only
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* lock reclaims.
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*/
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bool locks_in_grace(struct net *net)
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{
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return __state_in_grace(net, false);
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}
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EXPORT_SYMBOL_GPL(locks_in_grace);
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bool opens_in_grace(struct net *net)
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{
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return __state_in_grace(net, true);
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}
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EXPORT_SYMBOL_GPL(opens_in_grace);
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static int __net_init
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grace_init_net(struct net *net)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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INIT_LIST_HEAD(grace_list);
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return 0;
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}
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static void __net_exit
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grace_exit_net(struct net *net)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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WARN_ONCE(!list_empty(grace_list),
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"net %x %s: grace_list is not empty\n",
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net->ns.inum, __func__);
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}
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static struct pernet_operations grace_net_ops = {
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.init = grace_init_net,
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.exit = grace_exit_net,
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.id = &grace_net_id,
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.size = sizeof(struct list_head),
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};
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static int __init
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init_grace(void)
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{
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return register_pernet_subsys(&grace_net_ops);
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}
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static void __exit
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exit_grace(void)
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{
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unregister_pernet_subsys(&grace_net_ops);
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}
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MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
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MODULE_LICENSE("GPL");
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module_init(init_grace)
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module_exit(exit_grace)
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