From: andros@netapp.com Subject: [PATCH 2/2] nfs41: fix state manager deadlock in session reset Date: Wed, 11 Nov 2009 14:20:14 -0500 Message-ID: <1257967214-7068-3-git-send-email-andros@netapp.com> References: <1257967214-7068-1-git-send-email-andros@netapp.com> <1257967214-7068-2-git-send-email-andros@netapp.com> Cc: linux-nfs@vger.kernel.org, pnfs@linux-nfs.org, Andy Adamson To: trond.myklebust@netapp.com Return-path: Received: from mx2.netapp.com ([216.240.18.37]:4518 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758669AbZKKT1I (ORCPT ); Wed, 11 Nov 2009 14:27:08 -0500 In-Reply-To: <1257967214-7068-2-git-send-email-andros@netapp.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: From: Andy Adamson If the session is reset during state recovery, the state manager thread can sleep on the slot_tbl_waitq causing a deadlock. Add a completion framework to the session. Have the state manager thread set a new session state (NFS4CLNT_SESSION_DRAINING) and wait for the session slot table to drain. Signal the state manager thread in nfs41_sequence_free_slot when the NFS4CLNT_SESSION_DRAINING bit is set and the session is drained. Reported-by: Trond Myklebust Signed-off-by: Andy Adamson --- fs/nfs/nfs4_fs.h | 1 + fs/nfs/nfs4proc.c | 25 ++++++++++++++++--------- fs/nfs/nfs4state.c | 15 +++++++++++++++ include/linux/nfs_fs_sb.h | 1 + 4 files changed, 33 insertions(+), 9 deletions(-) diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h index 6ea07a3..e8604af 100644 --- a/fs/nfs/nfs4_fs.h +++ b/fs/nfs/nfs4_fs.h @@ -45,6 +45,7 @@ enum nfs4_client_state { NFS4CLNT_RECLAIM_NOGRACE, NFS4CLNT_DELEGRETURN, NFS4CLNT_SESSION_SETUP, + NFS4CLNT_SESSION_DRAINING, }; /* diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 44d1c14..ebde948 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -355,6 +355,16 @@ void nfs41_sequence_free_slot(const struct nfs_client *clp, } nfs4_free_slot(tbl, res->sr_slotid); res->sr_slotid = NFS4_MAX_SLOT_TABLE; + + /* Signal state manager thread if session is drained */ + if (test_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state)) { + spin_lock(&tbl->slot_tbl_lock); + if (tbl->highest_used_slotid == -1) { + dprintk("%s COMPLETE: Session Drained\n", __func__); + complete(&clp->cl_session->complete); + } + spin_unlock(&tbl->slot_tbl_lock); + } } static void nfs41_sequence_done(struct nfs_client *clp, @@ -448,15 +458,11 @@ static int nfs41_setup_sequence(struct nfs4_session *session, spin_lock(&tbl->slot_tbl_lock); if (test_bit(NFS4CLNT_SESSION_SETUP, &session->clp->cl_state)) { - if (tbl->highest_used_slotid != -1) { - rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL); - spin_unlock(&tbl->slot_tbl_lock); - dprintk("<-- %s: Session reset: draining\n", __func__); - return -EAGAIN; - } - - /* The slot table is empty; start the reset thread */ - dprintk("%s Session Reset\n", __func__); + /* + * The state manager will wait until the slot table is empty. + * Schedule the reset thread + */ + dprintk("%s Schedule Session Reset\n", __func__); rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL); nfs4_schedule_state_manager(session->clp); spin_unlock(&tbl->slot_tbl_lock); @@ -4583,6 +4589,7 @@ struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp) * nfs_client struct */ clp->cl_cons_state = NFS_CS_SESSION_INITING; + init_completion(&session->complete); tbl = &session->fc_slot_table; spin_lock_init(&tbl->slot_tbl_lock); diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 50a1b04..f08abe8 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -1162,8 +1162,23 @@ static void nfs4_session_recovery_handle_error(struct nfs_client *clp, int err) static int nfs4_reset_session(struct nfs_client *clp) { + struct nfs4_session *ses = clp->cl_session; + struct nfs4_slot_table *tbl = &ses->fc_slot_table; int status; + spin_lock(&tbl->slot_tbl_lock); + if (tbl->highest_used_slotid != -1) { + set_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state); + spin_unlock(&tbl->slot_tbl_lock); + status = wait_for_completion_interruptible(&ses->complete); + clear_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state); + if (status) /* -ERESTARTSYS */ + goto out; + INIT_COMPLETION(ses->complete); + } else { + spin_unlock(&tbl->slot_tbl_lock); + } + status = nfs4_proc_destroy_session(clp->cl_session); if (status && status != -NFS4ERR_BADSESSION && status != -NFS4ERR_DEADSESSION) { diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h index 320569e..34fc6be 100644 --- a/include/linux/nfs_fs_sb.h +++ b/include/linux/nfs_fs_sb.h @@ -209,6 +209,7 @@ struct nfs4_session { unsigned long session_state; u32 hash_alg; u32 ssv_len; + struct completion complete; /* The fore and back channel */ struct nfs4_channel_attrs fc_attrs; -- 1.6.0.6