bcachefs: kill INODE_LOCK, use lock_two_nondirectories()

In an ideal world, we'd have a common helper that could be used for
sorting a list of inodes into the correct lock order, and then the same
lock ordering could be used for any type of inode lock, not just
i_rwsem.

But the lock ordering rules for i_rwsem are a bit complicated, so -
abandon that dream for now and do it the more standard way.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs-io.c

@@ -861,7 +861,8 @@ loff_t bch2_remap_file_range(struct file *file_src, loff_t pos_src,
 	    abs(pos_src - pos_dst) < len)
 		return -EINVAL;
 
-	bch2_lock_inodes(INODE_LOCK|INODE_PAGECACHE_BLOCK, src, dst);
+	lock_two_nondirectories(&src->v, &dst->v);
+	bch2_lock_inodes(INODE_PAGECACHE_BLOCK, src, dst);
 
 	inode_dio_wait(&src->v);
 	inode_dio_wait(&dst->v);
@@ -914,7 +915,8 @@ loff_t bch2_remap_file_range(struct file *file_src, loff_t pos_src,
 		ret = bch2_flush_inode(c, dst);
 err:
 	bch2_quota_reservation_put(c, dst, &quota_res);
-	bch2_unlock_inodes(INODE_LOCK|INODE_PAGECACHE_BLOCK, src, dst);
+	bch2_unlock_inodes(INODE_PAGECACHE_BLOCK, src, dst);
+	unlock_two_nondirectories(&src->v, &dst->v);
 
 	return bch2_err_class(ret);
 }

fs/bcachefs/fs.h

@@ -77,9 +77,8 @@ static inline int ptrcmp(void *l, void *r)
 }
 
 enum bch_inode_lock_op {
-	INODE_LOCK		= (1U << 0),
-	INODE_PAGECACHE_BLOCK	= (1U << 1),
-	INODE_UPDATE_LOCK	= (1U << 2),
+	INODE_PAGECACHE_BLOCK	= (1U << 0),
+	INODE_UPDATE_LOCK	= (1U << 1),
 };
 
 #define bch2_lock_inodes(_locks, ...)					\
@@ -91,8 +90,6 @@ do {									\
 									\
 	for (i = 1; i < ARRAY_SIZE(a); i++)				\
 		if (a[i] != a[i - 1]) {					\
-			if ((_locks) & INODE_LOCK)			\
-				down_write_nested(&a[i]->v.i_rwsem, i);	\
 			if ((_locks) & INODE_PAGECACHE_BLOCK)		\
 				bch2_pagecache_block_get(a[i]);\
 			if ((_locks) & INODE_UPDATE_LOCK)			\
@@ -109,8 +106,6 @@ do {									\
 									\
 	for (i = 1; i < ARRAY_SIZE(a); i++)				\
 		if (a[i] != a[i - 1]) {					\
-			if ((_locks) & INODE_LOCK)			\
-				up_write(&a[i]->v.i_rwsem);		\
 			if ((_locks) & INODE_PAGECACHE_BLOCK)		\
 				bch2_pagecache_block_put(a[i]);\
 			if ((_locks) & INODE_UPDATE_LOCK)			\