hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBAFF1 -------------------------------- Unlinking file may cause the following deadlock in state manager: [root@localhost test]# cat /proc/2943/stack [<0>] rpc_wait_bit_killable+0x1a/0x90 [<0>] _nfs4_proc_delegreturn+0x60f/0x760 [<0>] nfs4_proc_delegreturn+0x13d/0x2a0 [<0>] nfs_do_return_delegation+0xba/0x110 [<0>] nfs_end_delegation_return+0x32c/0x620 [<0>] nfs_complete_unlink+0xc7/0x290 [<0>] nfs_dentry_iput+0x36/0x50 [<0>] __dentry_kill+0xaa/0x250 [<0>] dput.part.0+0x26c/0x4d0 [<0>] __put_nfs_open_context+0x1d9/0x260 [<0>] nfs4_open_reclaim+0x77/0xa0 [<0>] nfs4_do_reclaim+0x385/0xf40 [<0>] nfs4_state_manager+0x762/0x14e0 [<0>] nfs4_run_state_manager+0x181/0x330 [<0>] kthread+0x1a7/0x1f0 [<0>] ret_from_fork+0x34/0x60 [<0>] ret_from_fork_asm+0x1a/0x30 [root@localhost test]# It can be reproduced by following steps: 1) client: open file 2) client: unlink file 3) server: service restart(trigger state manager in client) 4) client: close file(in nfs4_open_reclaim, between nfs4_do_open_reclaim and put_nfs_open_context) Since the file has been open, unlinking will just set DCACHE_NFSFS_RENAMED for the dentry like this: nfs_unlink nfs_sillyrename nfs_async_unlink // set DCACHE_NFSFS_RENAMED Restarting service will trigger state manager in client. (1) NFS4_SLOT_TBL_DRAINING will be set to nfs4_slot_table since session has been reset. (2) DCACHE_NFSFS_RENAMED is detected in nfs_dentry_iput. Therefore, nfs_complete_unlink is called to trigger delegation return. (3) Due to the slot table being in draining state and sa_privileged being 0, the delegation return will be queued and wait. nfs4_state_manager nfs4_reset_session nfs4_begin_drain_session nfs4_drain_slot_tbl // set NFS4_SLOT_TBL_DRAINING (1) nfs4_do_reclaim nfs4_open_reclaim __put_nfs_open_context __dentry_kill nfs_dentry_iput // check DCACHE_NFSFS_RENAMED (2) nfs_complete_unlink nfs_end_delegation_return nfs_do_return_delegation nfs4_proc_delegreturn _nfs4_proc_delegreturn rpc_run_task ... nfs4_delegreturn_prepare nfs4_setup_sequence nfs4_slot_tbl_draining // check NFS4_SLOT_TBL_DRAINING // and sa_privileged is 0 (3) rpc_sleep_on // set queued and add to slot_tbl_waitq // rpc_task is async and wait in __rpc_execute rpc_wait_for_completion_task __rpc_wait_for_completion_task out_of_line_wait_on_bit rpc_wait_bit_killable // wait for rpc_task to complete <-------- can not get here to wake up rpc_task --------> nfs4_end_drain_session nfs4_end_drain_slot_table nfs41_wake_slot_table On the one hand, the state manager is blocked by the unfinished delegation return. As a result, nfs4_end_drain_session cannot be invoked to clear NFS4_SLOT_TBL_DRAINING and wake up waiting tasks. On the other hand, since NFS4_SLOT_TBL_DRAINING is not cleared, delegation return can only wait in the queue, resulting in a deadlock. Fix it by turning the delegation return into a privileged operation for the case where the nfs_client is in NFS4CLNT_RECLAIM_REBOOT state. Fixes: 977fcc2b0b41 ("NFS: Add a delegation return into nfs4_proc_unlink_setup()") Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com> --- fs/nfs/nfs4proc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 349994e18fd6..35c15d20a84e 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -6571,7 +6571,7 @@ static int _nfs4_proc_delegreturn(struct inode *inode, const struct cred *cred, } } - if (!data->inode) + if (!data->inode || test_bit(NFS4CLNT_RECLAIM_REBOOT, &server->nfs_client->cl_state)) nfs4_init_sequence(&data->args.seq_args, &data->res.seq_res, 1, 1); else -- 2.46.1