[tip: locking/core] NFSv4: Use sequence counter with associated spinlock

tip-bot2 for Ahmed S. Darwish
2020-07-29T14:33:39Z

The following commit has been merged into the locking/core branch of tip:

Commit-ID: 76246c9219726c71e3f470344d8c6a566fa2535b
Gitweb: https://git.kernel.org/tip/76246c9219726c71e3f470344d8c6a566fa2535b
Author: Ahmed S. Darwish <a.darwish@linutronix.de>
AuthorDate: Mon, 20 Jul 2020 17:55:27 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 29 Jul 2020 16:14:28 +02:00

NFSv4: Use sequence counter with associated spinlock

A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-22-a.darwish@linutronix.de
---
fs/nfs/nfs4_fs.h | 2 +-
fs/nfs/nfs4state.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 2b7f6dc..210e590 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -117,7 +117,7 @@ struct nfs4_state_owner {
unsigned long so_flags;
struct list_head so_states;
struct nfs_seqid_counter so_seqid;
- seqcount_t so_reclaim_seqcount;
+ seqcount_spinlock_t so_reclaim_seqcount;
struct mutex so_delegreturn_mutex;
};

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index a8dc25c..b1dba24 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -509,7 +509,7 @@ 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);
+ seqcount_spinlock_init(&sp->so_reclaim_seqcount, &sp->so_lock);
mutex_init(&sp->so_delegreturn_mutex);
return sp;
}