Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-qc0-f175.google.com ([209.85.216.175]:49028 "EHLO mail-qc0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbaFZTOw (ORCPT ); Thu, 26 Jun 2014 15:14:52 -0400 Received: by mail-qc0-f175.google.com with SMTP id i8so3524898qcq.6 for ; Thu, 26 Jun 2014 12:14:51 -0700 (PDT) From: Jeff Layton To: bfields@fieldses.org Cc: linux-nfs@vger.kernel.org Subject: [PATCH v2 048/117] nfsd: clean up races in lock stateid searching and creation Date: Thu, 26 Jun 2014 15:12:28 -0400 Message-Id: <1403810017-16062-49-git-send-email-jlayton@primarydata.com> In-Reply-To: <1403810017-16062-1-git-send-email-jlayton@primarydata.com> References: <1403810017-16062-1-git-send-email-jlayton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Preparation for removal of the client_mutex. Currently, no lock aside from the client_mutex is held when calling find_lock_state. Ensure that the cl_lock is held by adding a lockdep assertion. Once we remove the client_mutex, it'll be possible for another thread to race in and insert a lock state for the same file after we search but before we insert a new one. Ensure that doesn't happen by redoing the search after allocating a new stid that we plan to insert. If one is found just put the one we just allocated. Signed-off-by: Jeff Layton --- fs/nfsd/nfs4state.c | 58 +++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 41 insertions(+), 17 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index a3413cb4ac46..6e918aa0829c 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -4680,16 +4680,14 @@ alloc_init_lock_stateowner(unsigned int strhashval, struct nfs4_client *clp, str return lo; } -static struct nfs4_ol_stateid * -alloc_init_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp, struct nfs4_ol_stateid *open_stp) +static void +init_lock_stateid(struct nfs4_ol_stateid *stp, struct nfs4_lockowner *lo, + struct nfs4_file *fp, struct nfs4_ol_stateid *open_stp) { - struct nfs4_openowner *oo = openowner(open_stp->st_stateowner); - struct nfs4_ol_stateid *stp; struct nfs4_client *clp = lo->lo_owner.so_client; - stp = nfs4_alloc_stateid(clp); - if (stp == NULL) - return NULL; + lockdep_assert_held(&clp->cl_lock); + stp->st_stid.sc_type = NFS4_LOCK_STID; stp->st_stateowner = &lo->lo_owner; get_nfs4_file(fp); @@ -4698,20 +4696,20 @@ alloc_init_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp, struct stp->st_access_bmap = 0; stp->st_deny_bmap = open_stp->st_deny_bmap; stp->st_openstp = open_stp; - spin_lock(&oo->oo_owner.so_client->cl_lock); list_add(&stp->st_locks, &open_stp->st_locks); list_add(&stp->st_perstateowner, &lo->lo_owner.so_stateids); spin_lock(&fp->fi_lock); list_add(&stp->st_perfile, &fp->fi_stateids); spin_unlock(&fp->fi_lock); - spin_unlock(&oo->oo_owner.so_client->cl_lock); - return stp; } static struct nfs4_ol_stateid * find_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp) { struct nfs4_ol_stateid *lst; + struct nfs4_client *clp = lo->lo_owner.so_client; + + lockdep_assert_held(&clp->cl_lock); list_for_each_entry(lst, &lo->lo_owner.so_stateids, st_perstateowner) { if (lst->st_stid.sc_file == fp) @@ -4720,6 +4718,36 @@ find_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp) return NULL; } +static struct nfs4_ol_stateid * +find_or_create_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fi, + struct nfs4_ol_stateid *ost, bool *new) +{ + struct nfs4_ol_stateid *lst, *nst = NULL; + struct nfs4_openowner *oo = openowner(ost->st_stateowner); + struct nfs4_client *clp = oo->oo_owner.so_client; + + spin_lock(&clp->cl_lock); + lst = find_lock_stateid(lo, fi); + if (lst == NULL) { + spin_unlock(&clp->cl_lock); + nst = nfs4_alloc_stateid(clp); + if (nst == NULL) + return NULL; + + spin_lock(&clp->cl_lock); + lst = find_lock_stateid(lo, fi); + if (likely(!lst)) { + init_lock_stateid(nst, lo, fi, ost); + lst = nst; + nst = NULL; + *new = true; + } + } + spin_unlock(&clp->cl_lock); + if (nst) + put_generic_stateid(nst); + return lst; +} static int check_lock_length(u64 offset, u64 length) @@ -4763,14 +4791,10 @@ static __be32 lookup_or_create_lock_state(struct nfsd4_compound_state *cstate, s return nfserr_bad_seqid; } - *lst = find_lock_stateid(lo, fi); + *lst = find_or_create_lock_stateid(lo, fi, ost, new); if (*lst == NULL) { - *lst = alloc_init_lock_stateid(lo, fi, ost); - if (*lst == NULL) { - release_lockowner_if_empty(lo); - return nfserr_jukebox; - } - *new = true; + release_lockowner_if_empty(lo); + return nfserr_jukebox; } return nfs_ok; } -- 1.9.3