parallel lookups: actual switch to rwsem

ta-da!

The main issue is the lack of down_write_killable(), so the places
like readdir.c switched to plain inode_lock(); once killable
variants of rwsem primitives appear, that'll be dealt with.

lockdep side also might need more work

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 21 insertions, 6 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 00cecc5a2f75..3018f31f7aa0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -647,7 +647,7 @@ struct inode {
 
 	/* Misc */
 	unsigned long		i_state;
-	struct mutex		i_mutex;
+	struct rw_semaphore	i_rwsem;
 
 	unsigned long		dirtied_when;	/* jiffies of first dirtying */
 	unsigned long		dirtied_time_when;
@@ -734,27 +734,42 @@ enum inode_i_mutex_lock_class
 
 static inline void inode_lock(struct inode *inode)
 {
-	mutex_lock(&inode->i_mutex);
+	down_write(&inode->i_rwsem);
 }
 
 static inline void inode_unlock(struct inode *inode)
 {
-	mutex_unlock(&inode->i_mutex);
+	up_write(&inode->i_rwsem);
+}
+
+static inline void inode_lock_shared(struct inode *inode)
+{
+	down_read(&inode->i_rwsem);
+}
+
+static inline void inode_unlock_shared(struct inode *inode)
+{
+	up_read(&inode->i_rwsem);
 }
 
 static inline int inode_trylock(struct inode *inode)
 {
-	return mutex_trylock(&inode->i_mutex);
+	return down_write_trylock(&inode->i_rwsem);
+}
+
+static inline int inode_trylock_shared(struct inode *inode)
+{
+	return down_read_trylock(&inode->i_rwsem);
 }
 
 static inline int inode_is_locked(struct inode *inode)
 {
-	return mutex_is_locked(&inode->i_mutex);
+	return rwsem_is_locked(&inode->i_rwsem);
 }
 
 static inline void inode_lock_nested(struct inode *inode, unsigned subclass)
 {
-	mutex_lock_nested(&inode->i_mutex, subclass);
+	down_write_nested(&inode->i_rwsem, subclass);
 }
 
 void lock_two_nondirectories(struct inode *, struct inode*);