aufs: iinfo, debug by rwsem

This is a very old debugging routine for rw_semaphore I was using
privately and less meaningful to other people. It was (probably) before
LOCKDEP feature was introduced, but now it is based upon LOCKDEP. This
is compiled when CONFIG_AUFS_DEBUG is enabled.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/Kconfig

@@ -43,4 +43,10 @@ config AUFS_BRANCH_MAX_32767
 	in a single aufs. The larger value consumes more system
 	resources and has a minor impact to performance.
 endchoice
+
+config AUFS_DEBUG
+	bool "Debug aufs"
+	help
+	Enable this to compile aufs internal debug code.
+	It will have a negative impact to the performance.
 endif

fs/aufs/aufs.h

@@ -12,8 +12,11 @@
 
 #ifdef __KERNEL__
 
+#include "debug.h"
+
 #include "inode.h"
 #include "module.h"
+#include "rwsem.h"
 #include "super.h"
 
 #endif /* __KERNEL__ */

fs/aufs/iinfo.c

@@ -14,6 +14,8 @@ struct inode *au_h_iptr(struct inode *inode, aufs_bindex_t bindex)
 	struct inode *h_inode;
 	struct au_hinode *hinode;
 
+	IiMustAnyLock(inode);
+
 	hinode = au_hinode(au_ii(inode), bindex);
 	h_inode = hinode->hi_inode;
 	AuDebugOn(h_inode && atomic_read(&h_inode->i_count) <= 0);
@@ -33,6 +35,8 @@ void au_set_h_iptr(struct inode *inode, aufs_bindex_t bindex,
 	struct inode *hi;
 	struct au_iinfo *iinfo = au_ii(inode);
 
+	IiMustWriteLock(inode);
+
 	hinode = au_hinode(iinfo, bindex);
 	hi = hinode->hi_inode;
 	AuDebugOn(h_inode && atomic_read(&h_inode->i_count) <= 0);
@@ -55,8 +59,7 @@ void au_icntnr_init_once(void *_c)
 	struct au_icntnr *c = _c;
 	struct au_iinfo *iinfo = &c->iinfo;
 
-	init_rwsem(&iinfo->ii_rwsem);
-	down_write(&iinfo->ii_rwsem);
+	au_rw_init(&iinfo->ii_rwsem);
 	inode_init_once(&c->vfs_inode);
 }
 
@@ -108,4 +111,5 @@ void au_iinfo_fin(struct inode *inode)
 		}
 	}
 	au_kfree_small(iinfo->ii_hinode);
+	AuRwDestroy(&iinfo->ii_rwsem);
 }

fs/aufs/inode.h

@@ -13,13 +13,14 @@
 #ifdef __KERNEL__
 
 #include <linux/fs.h>
+#include "rwsem.h"
 
 struct au_hinode {
 	struct inode		*hi_inode;
 };
 
 struct au_iinfo {
-	struct rw_semaphore	ii_rwsem;
+	struct au_rwsem		ii_rwsem;
 	aufs_bindex_t		ii_btop, ii_bbot;
 	struct au_hinode	*ii_hinode;
 };
@@ -54,6 +55,64 @@ void au_iinfo_fin(struct inode *inode);
 
 /* ---------------------------------------------------------------------- */
 
+/* lock subclass for iinfo */
+enum {
+	AuLsc_II_CHILD,		/* child first */
+	AuLsc_II_CHILD2,	/* rename(2), link(2), and cpup at hnotify */
+	AuLsc_II_CHILD3,	/* copyup dirs */
+	AuLsc_II_PARENT,	/* see AuLsc_I_PARENT in vfsub.h */
+	AuLsc_II_PARENT2,
+	AuLsc_II_PARENT3,	/* copyup dirs */
+	AuLsc_II_NEW_CHILD
+};
+
+/*
+ * ii_read_lock_child, ii_write_lock_child,
+ * ii_read_lock_child2, ii_write_lock_child2,
+ * ii_read_lock_child3, ii_write_lock_child3,
+ * ii_read_lock_parent, ii_write_lock_parent,
+ * ii_read_lock_parent2, ii_write_lock_parent2,
+ * ii_read_lock_parent3, ii_write_lock_parent3,
+ * ii_read_lock_new_child, ii_write_lock_new_child,
+ */
+#define AuReadLockFunc(name, lsc) \
+static inline void ii_read_lock_##name(struct inode *i) \
+{ \
+	au_rw_read_lock_nested(&au_ii(i)->ii_rwsem, AuLsc_II_##lsc); \
+}
+
+#define AuWriteLockFunc(name, lsc) \
+static inline void ii_write_lock_##name(struct inode *i) \
+{ \
+	au_rw_write_lock_nested(&au_ii(i)->ii_rwsem, AuLsc_II_##lsc); \
+}
+
+#define AuRWLockFuncs(name, lsc) \
+	AuReadLockFunc(name, lsc) \
+	AuWriteLockFunc(name, lsc)
+
+AuRWLockFuncs(child, CHILD);
+AuRWLockFuncs(child2, CHILD2);
+AuRWLockFuncs(child3, CHILD3);
+AuRWLockFuncs(parent, PARENT);
+AuRWLockFuncs(parent2, PARENT2);
+AuRWLockFuncs(parent3, PARENT3);
+AuRWLockFuncs(new_child, NEW_CHILD);
+
+#undef AuReadLockFunc
+#undef AuWriteLockFunc
+#undef AuRWLockFuncs
+
+#define ii_read_unlock(i)	au_rw_read_unlock(&au_ii(i)->ii_rwsem)
+#define ii_write_unlock(i)	au_rw_write_unlock(&au_ii(i)->ii_rwsem)
+#define ii_downgrade_lock(i)	au_rw_dgrade_lock(&au_ii(i)->ii_rwsem)
+
+#define IiMustNoWaiters(i)	AuRwMustNoWaiters(&au_ii(i)->ii_rwsem)
+#define IiMustAnyLock(i)	AuRwMustAnyLock(&au_ii(i)->ii_rwsem)
+#define IiMustWriteLock(i)	AuRwMustWriteLock(&au_ii(i)->ii_rwsem)
+
+/* ---------------------------------------------------------------------- */
+
 static inline void au_icntnr_init(struct au_icntnr *c)
 {
 	/* re-commit later */
@@ -74,26 +133,31 @@ static inline int au_is_bad_inode(struct inode *inode)
 
 static inline aufs_bindex_t au_ibtop(struct inode *inode)
 {
+	IiMustAnyLock(inode);
 	return au_ii(inode)->ii_btop;
 }
 
 static inline aufs_bindex_t au_ibbot(struct inode *inode)
 {
+	IiMustAnyLock(inode);
 	return au_ii(inode)->ii_bbot;
 }
 
 static inline void au_set_ibtop(struct inode *inode, aufs_bindex_t bindex)
 {
+	IiMustWriteLock(inode);
 	au_ii(inode)->ii_btop = bindex;
 }
 
 static inline void au_set_ibbot(struct inode *inode, aufs_bindex_t bindex)
 {
+	IiMustWriteLock(inode);
 	au_ii(inode)->ii_bbot = bindex;
 }
 
 static inline struct au_hinode *au_hi(struct inode *inode, aufs_bindex_t bindex)
 {
+	IiMustAnyLock(inode);
 	return au_hinode(au_ii(inode), bindex);
 }
 

fs/aufs/rwsem.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2019 Junjiro R. Okajima
+ */
+
+/*
+ * simple read-write semaphore wrappers
+ */
+
+#ifndef __AUFS_RWSEM_H__
+#define __AUFS_RWSEM_H__
+
+#ifdef __KERNEL__
+
+#include "debug.h"
+
+/* in the future, the name 'au_rwsem' will be totally gone */
+#define au_rwsem	rw_semaphore
+
+/* to debug easier, do not make them inlined functions */
+#define AuRwMustNoWaiters(rw)	AuDebugOn(rwsem_is_contended(rw))
+/* rwsem_is_locked() is unusable */
+#define AuRwMustReadLock(rw)	AuDebugOn(!lockdep_recursing(current) \
+					  && debug_locks \
+					  && !lockdep_is_held_type(rw, 1))
+#define AuRwMustWriteLock(rw)	AuDebugOn(!lockdep_recursing(current) \
+					  && debug_locks \
+					  && !lockdep_is_held_type(rw, 0))
+#define AuRwMustAnyLock(rw)	AuDebugOn(!lockdep_recursing(current) \
+					  && debug_locks \
+					  && !lockdep_is_held(rw))
+#define AuRwDestroy(rw)		AuDebugOn(!lockdep_recursing(current) \
+					  && debug_locks \
+					  && lockdep_is_held(rw))
+
+#define au_rw_init(rw)	init_rwsem(rw)
+
+#define au_rw_init_wlock(rw) do {		\
+		au_rw_init(rw);			\
+		down_write(rw);			\
+	} while (0)
+
+#define au_rw_init_wlock_nested(rw, lsc) do {	\
+		au_rw_init(rw);			\
+		down_write_nested(rw, lsc);	\
+	} while (0)
+
+#define au_rw_read_lock(rw)		down_read(rw)
+#define au_rw_read_lock_nested(rw, lsc)	down_read_nested(rw, lsc)
+#define au_rw_read_unlock(rw)		up_read(rw)
+#define au_rw_dgrade_lock(rw)		downgrade_write(rw)
+#define au_rw_write_lock(rw)		down_write(rw)
+#define au_rw_write_lock_nested(rw, lsc) down_write_nested(rw, lsc)
+#define au_rw_write_unlock(rw)		up_write(rw)
+/* why is not _nested version defined? */
+#define au_rw_read_trylock(rw)		down_read_trylock(rw)
+#define au_rw_write_trylock(rw)		down_write_trylock(rw)
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_RWSEM_H__ */