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

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 2b7f6dcd2eb82e0adc9342b03a92dc396d4260b2..210e590e1f7187b8459a4eafe2a54ecfde7c5900 100644 (file)
--- 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 a8dc25ce48bba8543234b2bb5fbef8999db76bb5..b1dba24918f806139108645d424eb48e7af1180c 100644 (file)
--- 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;
 }