From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Vasily Averin <vvs@virtuozzo.com>,
        Bruce Fields <bfields@fieldses.org>
CC:     Jeff Layton <jlayton@kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH] nfsd: don't put blocked locks on LRU until after
 vfs_lock_file returns
Thread-Topic: [PATCH] nfsd: don't put blocked locks on LRU until after
 vfs_lock_file returns
Thread-Index: AQHX4GTIZQ8O/Wal+UKjnqXW3Az4WawROmkAgAAAb4A=
Date:   Tue, 23 Nov 2021 15:21:42 +0000
Message-ID: <3E5336E5-1FCF-4E9C-A10A-251834C6BA17@oracle.com>
References: <20211123122223.69236-1-jlayton@kernel.org>
 <d3f68639-3f07-dbf7-9a4d-984fdd7bd62f@virtuozzo.com>
In-Reply-To: <d3f68639-3f07-dbf7-9a4d-984fdd7bd62f@virtuozzo.com>
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> On Nov 23, 2021, at 10:20 AM, Vasily Averin <vvs@virtuozzo.com> wrote:
>=20
> On 23.11.2021 15:22, Jeff Layton wrote:
>> Vasily reported a case where vfs_lock_file took a very long time to
>> return (longer than a lease period). The laundromat eventually ran and
>> reaped the thing and when the vfs_lock_file returned, it ended up
>> accessing freed memory.
>>=20
>> Don't put entries onto the LRU until vfs_lock_file returns.
>=20
> Cc: stable@vger.kernel.org
> Fixes: 7919d0a27f1e "nfsd: add a LRU list for blocked locks"
>=20
>> Reported-by: Vasily Averin <vvs@virtuozzo.com>
>> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> Tested-by: Vasily Averin <vvs@virtuozzo.com>

I assume Bruce is grabbing this for v5.16-rc.


>> ---
>> fs/nfsd/nfs4state.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>=20
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index bfad94c70b84..8cfef84b9355 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -6966,10 +6966,8 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_c=
ompound_state *cstate,
>> 	}
>>=20
>> 	if (fl_flags & FL_SLEEP) {
>> -		nbl->nbl_time =3D ktime_get_boottime_seconds();
>> 		spin_lock(&nn->blocked_locks_lock);
>> 		list_add_tail(&nbl->nbl_list, &lock_sop->lo_blocked);
>> -		list_add_tail(&nbl->nbl_lru, &nn->blocked_locks_lru);
>> 		spin_unlock(&nn->blocked_locks_lock);
>> 	}
>>=20
>> @@ -6982,6 +6980,10 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_c=
ompound_state *cstate,
>> 			nn->somebody_reclaimed =3D true;
>> 		break;
>> 	case FILE_LOCK_DEFERRED:
>> +		nbl->nbl_time =3D ktime_get_boottime_seconds();
>> +		spin_lock(&nn->blocked_locks_lock);
>> +		list_add_tail(&nbl->nbl_lru, &nn->blocked_locks_lru);
>> +		spin_unlock(&nn->blocked_locks_lock);
>> 		nbl =3D NULL;
>> 		fallthrough;
>> 	case -EAGAIN:		/* conflock holds conflicting lock */
>>=20
>=20

--
Chuck Lever