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Date: Fri, 28 Oct 2016 23:05:11 +0200
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>,
linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de
Subject: NFSv4: replace seqcount_t with a seqlock_t
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.13-rt7.tar.xz
The raw_write_seqcount_begin() in nfs4_reclaim_open_state() causes a
preempt_disable() on -RT. The spin_lock()/spin_unlock() in that section does
not work.
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 <xiaolong.ye@intel.com>
Link: https://lkml.kernel.org/r/20161021164727.24485-1-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
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(-)
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -162,11 +162,11 @@ static int nfs_delegation_claim_opens(st
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);
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -115,7 +115,7 @@ 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;
};
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2965,7 +2965,7 @@ static int _nfs4_open_and_get_state(stru
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)
@@ -3007,7 +3007,7 @@ static int _nfs4_open_and_get_state(stru
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);
}
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -510,7 +510,7 @@ nfs4_alloc_state_owner(struct nfs_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;
}
@@ -1618,8 +1618,12 @@ static int nfs4_reclaim_open_state(struc
* recovering after a network partition or a reboot from a
* server that doesn't support a grace period.
*/
+#ifdef CONFIG_PREEMPT_RT
+ 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))
@@ -1680,14 +1684,20 @@ static int nfs4_reclaim_open_state(struc
spin_lock(&sp->so_lock);
goto restart;
}
- raw_write_seqcount_end(&sp->so_reclaim_seqcount);
spin_unlock(&sp->so_lock);
+#ifdef CONFIG_PREEMPT_RT
+ 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
+ write_sequnlock(&sp->so_reclaim_seqlock);
+#else
+ write_seqcount_end(&sp->so_reclaim_seqlock.seqcount);
+#endif
return status;
}
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