From: Sebastian Andrzej Siewior Date: Fri, 28 Oct 2016 23:05:11 +0200 Subject: [PATCH 025/342] NFSv4: replace seqcount_t with a seqlock_t Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=b840fb9c0979726ce4cf8e6136da1ce9be6baeb8 The raw_write_seqcount_begin() in nfs4_reclaim_open_state() bugs me because it maps to preempt_disable() in -RT which I can't have at this point. So I took a look at the code. It the lockdep part was removed in commit abbec2da13f0 ("NFS: Use raw_write_seqcount_begin/end int nfs4_reclaim_open_state") because lockdep complained. The whole seqcount thing was introduced in commit c137afabe330 ("NFSv4: Allow the state manager to mark an open_owner as being recovered"). The recovery threads runs only once. write_seqlock() does not work on !RT because it disables preemption and it the writer side is preemptible (has to remain so despite the fact that it will block readers). Reported-by: kernel test robot Signed-off-by: Sebastian Andrzej Siewior --- fs/nfs/delegation.c | 4 ++-- fs/nfs/nfs4_fs.h | 2 +- fs/nfs/nfs4proc.c | 4 ++-- fs/nfs/nfs4state.c | 22 ++++++++++++++++------ 4 files changed, 21 insertions(+), 11 deletions(-) diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c index b0c0c2fc2fba..26565ba05dc1 100644 --- a/fs/nfs/delegation.c +++ b/fs/nfs/delegation.c @@ -162,11 +162,11 @@ static int nfs_delegation_claim_opens(struct inode *inode, sp = state->owner; /* Block nfs4_proc_unlck */ mutex_lock(&sp->so_delegreturn_mutex); - seq = raw_seqcount_begin(&sp->so_reclaim_seqcount); + seq = read_seqbegin(&sp->so_reclaim_seqlock); err = nfs4_open_delegation_recall(ctx, state, stateid); if (!err) err = nfs_delegation_claim_locks(state, stateid); - if (!err && read_seqcount_retry(&sp->so_reclaim_seqcount, seq)) + if (!err && read_seqretry(&sp->so_reclaim_seqlock, seq)) err = -EAGAIN; mutex_unlock(&sp->so_delegreturn_mutex); put_nfs_open_context(ctx); diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h index 5ac7bf24c507..b15a7a2f64fe 100644 --- a/fs/nfs/nfs4_fs.h +++ b/fs/nfs/nfs4_fs.h @@ -114,7 +114,7 @@ struct nfs4_state_owner { unsigned long so_flags; struct list_head so_states; struct nfs_seqid_counter so_seqid; - seqcount_t so_reclaim_seqcount; + seqlock_t so_reclaim_seqlock; struct mutex so_delegreturn_mutex; }; diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index f48a11fa78bb..93dcfcd1424d 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -2874,7 +2874,7 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata, unsigned int seq; int ret; - seq = raw_seqcount_begin(&sp->so_reclaim_seqcount); + seq = raw_seqcount_begin(&sp->so_reclaim_seqlock.seqcount); ret = _nfs4_proc_open(opendata, ctx); if (ret != 0) @@ -2915,7 +2915,7 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata, if (d_inode(dentry) == state->inode) { nfs_inode_attach_open_context(ctx); - if (read_seqcount_retry(&sp->so_reclaim_seqcount, seq)) + if (read_seqretry(&sp->so_reclaim_seqlock, seq)) nfs4_schedule_stateid_recovery(server, state); } diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 30576a10a1f4..e0b94cbce3bf 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -516,7 +516,7 @@ nfs4_alloc_state_owner(struct nfs_server *server, nfs4_init_seqid_counter(&sp->so_seqid); atomic_set(&sp->so_count, 1); INIT_LIST_HEAD(&sp->so_lru); - seqcount_init(&sp->so_reclaim_seqcount); + seqlock_init(&sp->so_reclaim_seqlock); mutex_init(&sp->so_delegreturn_mutex); return sp; } @@ -1584,8 +1584,12 @@ static int nfs4_reclaim_open_state(struct nfs4_state_owner *sp, const struct nfs * recovering after a network partition or a reboot from a * server that doesn't support a grace period. */ +#ifdef CONFIG_PREEMPT_RT_FULL + write_seqlock(&sp->so_reclaim_seqlock); +#else + write_seqcount_begin(&sp->so_reclaim_seqlock.seqcount); +#endif spin_lock(&sp->so_lock); - raw_write_seqcount_begin(&sp->so_reclaim_seqcount); restart: list_for_each_entry(state, &sp->so_states, open_states) { if (!test_and_clear_bit(ops->state_flag_bit, &state->flags)) @@ -1672,14 +1676,20 @@ static int nfs4_reclaim_open_state(struct nfs4_state_owner *sp, const struct nfs spin_lock(&sp->so_lock); goto restart; } - raw_write_seqcount_end(&sp->so_reclaim_seqcount); spin_unlock(&sp->so_lock); +#ifdef CONFIG_PREEMPT_RT_FULL + write_sequnlock(&sp->so_reclaim_seqlock); +#else + write_seqcount_end(&sp->so_reclaim_seqlock.seqcount); +#endif return 0; out_err: nfs4_put_open_state(state); - spin_lock(&sp->so_lock); - raw_write_seqcount_end(&sp->so_reclaim_seqcount); - spin_unlock(&sp->so_lock); +#ifdef CONFIG_PREEMPT_RT_FULL + write_sequnlock(&sp->so_reclaim_seqlock); +#else + write_seqcount_end(&sp->so_reclaim_seqlock.seqcount); +#endif return status; }