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Message-ID: <d4c3b347-477f-4016-8093-edac22213cec@huawei.com>
Date: Thu, 13 Feb 2025 20:28:02 +0800
From: Li Lingfeng <lilingfeng3@...wei.com>
To: Jeff Layton <jlayton@...nel.org>, <chuck.lever@...cle.com>,
<neilb@...e.de>, <okorniev@...hat.com>, <Dai.Ngo@...cle.com>,
<tom@...pey.com>, <linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <yukuai1@...weicloud.com>, <houtao1@...wei.com>, <yi.zhang@...wei.com>,
<yangerkun@...wei.com>, <lilingfeng@...weicloud.com>
Subject: Re: [PATCH] nfsd: put dl_stid if fail to queue dl_recall
在 2025/2/13 19:49, Jeff Layton 写道:
> On Thu, 2025-02-13 at 15:25 +0800, Li Lingfeng wrote:
>> Before calling nfsd4_run_cb to queue dl_recall to the callback_wq, we
>> increment the reference count of dl_stid.
>> We expect that after the corresponding work_struct is processed, the
>> reference count of dl_stid will be decremented through the callback
>> function nfsd4_cb_recall_release.
>> However, if the call to nfsd4_run_cb fails, the incremented reference
>> count of dl_stid will not be decremented correspondingly, leading to the
>> following nfs4_stid leak:
>> unreferenced object 0xffff88812067b578 (size 344):
>> comm "nfsd", pid 2761, jiffies 4295044002 (age 5541.241s)
>> hex dump (first 32 bytes):
>> 01 00 00 00 6b 6b 6b 6b b8 02 c0 e2 81 88 ff ff ....kkkk........
>> 00 6b 6b 6b 6b 6b 6b 6b 00 00 00 00 ad 4e ad de .kkkkkkk.....N..
>> backtrace:
>> kmem_cache_alloc+0x4b9/0x700
>> nfsd4_process_open1+0x34/0x300
>> nfsd4_open+0x2d1/0x9d0
>> nfsd4_proc_compound+0x7a2/0xe30
>> nfsd_dispatch+0x241/0x3e0
>> svc_process_common+0x5d3/0xcc0
>> svc_process+0x2a3/0x320
>> nfsd+0x180/0x2e0
>> kthread+0x199/0x1d0
>> ret_from_fork+0x30/0x50
>> ret_from_fork_asm+0x1b/0x30
>> unreferenced object 0xffff8881499f4d28 (size 368):
>> comm "nfsd", pid 2761, jiffies 4295044005 (age 5541.239s)
>> hex dump (first 32 bytes):
>> 01 00 00 00 00 00 00 00 30 4d 9f 49 81 88 ff ff ........0M.I....
>> 30 4d 9f 49 81 88 ff ff 20 00 00 00 01 00 00 00 0M.I.... .......
>> backtrace:
>> kmem_cache_alloc+0x4b9/0x700
>> nfs4_alloc_stid+0x29/0x210
>> alloc_init_deleg+0x92/0x2e0
>> nfs4_set_delegation+0x284/0xc00
>> nfs4_open_delegation+0x216/0x3f0
>> nfsd4_process_open2+0x2b3/0xee0
>> nfsd4_open+0x770/0x9d0
>> nfsd4_proc_compound+0x7a2/0xe30
>> nfsd_dispatch+0x241/0x3e0
>> svc_process_common+0x5d3/0xcc0
>> svc_process+0x2a3/0x320
>> nfsd+0x180/0x2e0
>> kthread+0x199/0x1d0
>> ret_from_fork+0x30/0x50
>> ret_from_fork_asm+0x1b/0x30
>> Fix it by checking the result of nfsd4_run_cb and call nfs4_put_stid if
>> fail to queue dl_recall.
>>
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Signed-off-by: Li Lingfeng <lilingfeng3@...wei.com>
>> ---
>> fs/nfsd/nfs4state.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index 153eeea2c7c9..0ccb87be47b7 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -5414,6 +5414,7 @@ static const struct nfsd4_callback_ops nfsd4_cb_recall_ops = {
>>
>> static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
>> {
>> + bool queued;
>> /*
>> * We're assuming the state code never drops its reference
>> * without first removing the lease. Since we're in this lease
>> @@ -5422,7 +5423,10 @@ static void nfsd_break_one_deleg(struct nfs4_delegation *dp)
>> * we know it's safe to take a reference.
>> */
>> refcount_inc(&dp->dl_stid.sc_count);
>> - WARN_ON_ONCE(!nfsd4_run_cb(&dp->dl_recall));
>> + queued = nfsd4_run_cb(&dp->dl_recall);
>> + WARN_ON_ONCE(!queued);
>> + if (!queued)
>> + nfs4_put_stid(&dp->dl_stid);
>> }
>>
>> /* Called from break_lease() with flc_lock held. */
>
> Have you actually seen the WARN_ON_ONCE() pop under normal usage, or
> was the problem you reproduced done via fault injection?
Hi,
I add mdelay for cb_work before processing it and add msleep in
nfs_do_return_delegation to reproduce it.
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1188,6 +1188,8 @@ alloc_init_deleg(struct nfs4_client *clp, struct
nfs4_file *fp,
dp->dl_recalled = false;
nfsd4_init_cb(&dp->dl_recall, dp->dl_stid.sc_client,
&nfsd4_cb_recall_ops, NFSPROC4_CLNT_CB_RECALL);
+ dp->dl_recall.cb_work.debug_flag = 0x1234;
+ printk("%s init work func %px\n", __func__,
dp->dl_recall.cb_work.func);
get_nfs4_file(fp);
dp->dl_stid.sc_file = fp;
return dp;
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2708,6 +2708,12 @@ static void process_scheduled_works(struct worker
*worker)
worker->pool->watchdog_ts = jiffies;
first = false;
}
+ if (work->debug_flag == 0x1234) {
+ printk("%s func %px\n", __func__, work->func);
+ printk("%s delay before clear pending...\n", __func__);
+ mdelay(10 * 1000);
+ printk("%s delay done\n", __func__);
+ }
process_one_work(worker, work);
}
}
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -263,6 +263,15 @@ static int nfs_do_return_delegation(struct inode
*inode, struct nfs_delegation *
const struct cred *cred;
int res = 0;
+ printk("sleep before deleg return...\n");
+ while (1) {
+ ifdebug(PROC)
+ msleep(10 * 1000);
+ else
+ break;
+ }
+ printk("sleep done\n");
+
if (!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags)) {
spin_lock(&delegation->lock);
cred = get_cred(delegation->cred);
> Unfortunately, this won't work. nfsd_break_one_deleg() is called from
> the ->break_lease callback with the flc->flc_lock held, and
> nfs4_put_stid can sleep in the sc_free callbacks.
Are you referring to nfs4_free_deleg? I didn't quite see where it might
sleep. Could you please explain it to me?
Thanks.
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