bcachefs: fix seqmutex_relock()

We were grabbing the sequence number before unlock incremented it - fix
this by moving the increment to seqmutex_lock() (so the seqmutex_relock()
failure path skips the mutex_trylock()), and returning the sequence
number from unlock(), to make the API simpler and safer.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 4 insertions, 7 deletions

diff --git a/fs/bcachefs/seqmutex.h b/fs/bcachefs/seqmutex.h
index c1860d8163fb..c4b3d8d3f414 100644
--- a/fs/bcachefs/seqmutex.h
+++ b/fs/bcachefs/seqmutex.h
@@ -19,17 +19,14 @@ static inline bool seqmutex_trylock(struct seqmutex *lock)
 static inline void seqmutex_lock(struct seqmutex *lock)
 {
 	mutex_lock(&lock->lock);
-}
-
-static inline void seqmutex_unlock(struct seqmutex *lock)
-{
 	lock->seq++;
-	mutex_unlock(&lock->lock);
 }
 
-static inline u32 seqmutex_seq(struct seqmutex *lock)
+static inline u32 seqmutex_unlock(struct seqmutex *lock)
 {
-	return lock->seq;
+	u32 seq = lock->seq;
+	mutex_unlock(&lock->lock);
+	return seq;
 }
 
 static inline bool seqmutex_relock(struct seqmutex *lock, u32 seq)