Return-Path: Received: from discipline.rit.edu ([129.21.6.207]:26599 "HELO discipline.rit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1030447AbbKFBMV (ORCPT ); Thu, 5 Nov 2015 20:12:21 -0500 From: Andrew Elble To: linux-nfs@vger.kernel.org, bfields@fieldses.org, jlayton@poochiereds.net Cc: Andrew Elble Subject: [PATCH RFC v3] nfsd: fix race with open / open upgrade stateids Date: Thu, 5 Nov 2015 20:11:48 -0500 Message-Id: <1446772308-98705-1-git-send-email-aweits@rit.edu> Sender: linux-nfs-owner@vger.kernel.org List-ID: We observed multiple open stateids on the server for files that seemingly should have been closed. nfsd4_process_open2() tests for the existence of a preexisting stateid. If one is not found, the locks are dropped and a new one is created. The problem is that init_open_stateid(), which is also responsible for hashing the newly initialized stateid, doesn't check to see if another open has raced in and created a matching stateid. This fix is to enable init_open_stateid() to return the matching stateid and have nfsd4_process_open2() swap to that stateid and switch to the open upgrade path. In testing this patch, coverage to the newly created path indicates that the race was indeed happening. Signed-off-by: Andrew Elble --- v3: fixed missing down_read() before nfs4_get_vfs_file() fs/nfsd/nfs4state.c | 108 ++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 83 insertions(+), 25 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 637d1e92c606..9358d857a6d9 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -3345,6 +3345,40 @@ static const struct nfs4_stateowner_operations openowner_ops = { .so_free = nfs4_free_openowner, }; +/** + * nfsd4_find_existing_open - Find an existing open stateid for this openowner + * @fp: a pointer to an nfs4_file + * @open: a pointer to an nfsd4_open + * + * Return: + * On success: a pointer to the nfs4_ol_stateid that was found + * matching this nfs4_file and openowner. + * + * On error: NULL if an existing stateid was not found + * + */ + +static struct nfs4_ol_stateid * +nfsd4_find_existing_open(struct nfs4_file *fp, struct nfsd4_open *open) +{ + struct nfs4_ol_stateid *local, *ret = NULL; + struct nfs4_openowner *oo = open->op_openowner; + + lockdep_assert_held(&fp->fi_lock); + + list_for_each_entry(local, &fp->fi_stateids, st_perfile) { + /* ignore lock owners */ + if (local->st_stateowner->so_is_open_owner == 0) + continue; + if (local->st_stateowner == &oo->oo_owner) { + ret = local; + atomic_inc(&ret->st_stid.sc_count); + break; + } + } + return ret; +} + static struct nfs4_openowner * alloc_init_open_stateowner(unsigned int strhashval, struct nfsd4_open *open, struct nfsd4_compound_state *cstate) @@ -3376,9 +3410,37 @@ alloc_init_open_stateowner(unsigned int strhashval, struct nfsd4_open *open, return ret; } -static void init_open_stateid(struct nfs4_ol_stateid *stp, struct nfs4_file *fp, struct nfsd4_open *open) { +/** + * init_open_stateid - initialize a nfs4_ol_stateid structure and hash it + * @stp: a pointer to a freshly allocated nfs4_ol_stateid + * @fp: a pointer to an nfs4_file + * @open: a pointer to an nfsd4_open + * + * Return: + * On success: NULL if an existing stateid was not found + * matching this nfs4_file and openowner, and the + * new nfs4_ol_stateid was hashed. + * + * On error: a pointer to the existing stateid that was found + * matching this nfs4_file and openowner. The passed-in + * stateid is not hashed. + * + */ + +static struct nfs4_ol_stateid * +init_open_stateid(struct nfs4_ol_stateid *stp, struct nfs4_file *fp, + struct nfsd4_open *open) +{ + struct nfs4_openowner *oo = open->op_openowner; + struct nfs4_ol_stateid *retstp = NULL; + spin_lock(&oo->oo_owner.so_client->cl_lock); + spin_lock(&fp->fi_lock); + + retstp = nfsd4_find_existing_open(fp, open); + if (retstp) + goto out_unlock; atomic_inc(&stp->st_stid.sc_count); stp->st_stid.sc_type = NFS4_OPEN_STID; INIT_LIST_HEAD(&stp->st_locks); @@ -3389,12 +3451,13 @@ static void init_open_stateid(struct nfs4_ol_stateid *stp, struct nfs4_file *fp, stp->st_deny_bmap = 0; stp->st_openstp = NULL; init_rwsem(&stp->st_rwsem); - spin_lock(&oo->oo_owner.so_client->cl_lock); list_add(&stp->st_perstateowner, &oo->oo_owner.so_stateids); - spin_lock(&fp->fi_lock); list_add(&stp->st_perfile, &fp->fi_stateids); + +out_unlock: spin_unlock(&fp->fi_lock); spin_unlock(&oo->oo_owner.so_client->cl_lock); + return retstp; } /* @@ -3805,27 +3868,6 @@ out: return nfs_ok; } -static struct nfs4_ol_stateid * -nfsd4_find_existing_open(struct nfs4_file *fp, struct nfsd4_open *open) -{ - struct nfs4_ol_stateid *local, *ret = NULL; - struct nfs4_openowner *oo = open->op_openowner; - - spin_lock(&fp->fi_lock); - list_for_each_entry(local, &fp->fi_stateids, st_perfile) { - /* ignore lock owners */ - if (local->st_stateowner->so_is_open_owner == 0) - continue; - if (local->st_stateowner == &oo->oo_owner) { - ret = local; - atomic_inc(&ret->st_stid.sc_count); - break; - } - } - spin_unlock(&fp->fi_lock); - return ret; -} - static inline int nfs4_access_to_access(u32 nfs4_access) { int flags = 0; @@ -4189,6 +4231,7 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf struct nfs4_client *cl = open->op_openowner->oo_owner.so_client; struct nfs4_file *fp = NULL; struct nfs4_ol_stateid *stp = NULL; + struct nfs4_ol_stateid *swapstp = NULL; struct nfs4_delegation *dp = NULL; __be32 status; @@ -4202,7 +4245,9 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf status = nfs4_check_deleg(cl, open, &dp); if (status) goto out; + spin_lock(&fp->fi_lock); stp = nfsd4_find_existing_open(fp, open); + spin_unlock(&fp->fi_lock); } else { open->op_file = NULL; status = nfserr_bad_stateid; @@ -4225,7 +4270,19 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf } else { stp = open->op_stp; open->op_stp = NULL; - init_open_stateid(stp, fp, open); + swapstp = init_open_stateid(stp, fp, open); + if (swapstp) { + nfs4_put_stid(&stp->st_stid); + stp = swapstp; + down_read(&stp->st_rwsem); + status = nfs4_upgrade_open(rqstp, fp, current_fh, + stp, open); + if (status) { + up_read(&stp->st_rwsem); + goto out; + } + goto upgrade_out; + } down_read(&stp->st_rwsem); status = nfs4_get_vfs_file(rqstp, fp, current_fh, stp, open); if (status) { @@ -4239,6 +4296,7 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf if (stp->st_clnt_odstate == open->op_odstate) open->op_odstate = NULL; } +upgrade_out: nfs4_inc_and_copy_stateid(&open->op_stateid, &stp->st_stid); up_read(&stp->st_rwsem); -- 2.4.6