erofs: get rid of buf->kmap_type

After commit 927e501 ("erofs: use kmap_local_page() only for
erofs_bread()"), `buf->kmap_type` actually has no use at all.

Let's get rid of `buf->kmap_type` now.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241114095813.839866-1-hsiangkao@linux.alibaba.com

Author: hsiangkao

fs/erofs/data.c

@@ -10,10 +10,10 @@
 
 void erofs_unmap_metabuf(struct erofs_buf *buf)
 {
-	if (buf->kmap_type == EROFS_KMAP)
-		kunmap_local(buf->base);
+	if (!buf->base)
+		return;
+	kunmap_local(buf->base);
 	buf->base = NULL;
-	buf->kmap_type = EROFS_NO_KMAP;
 }
 
 void erofs_put_metabuf(struct erofs_buf *buf)
@@ -43,15 +43,8 @@ void *erofs_bread(struct erofs_buf *buf, erofs_off_t offset,
 			return folio;
 	}
 	buf->page = folio_file_page(folio, index);
-
-	if (buf->kmap_type == EROFS_NO_KMAP) {
-		if (type == EROFS_KMAP)
-			buf->base = kmap_local_page(buf->page);
-		buf->kmap_type = type;
-	} else if (buf->kmap_type != type) {
-		DBG_BUGON(1);
-		return ERR_PTR(-EFAULT);
-	}
+	if (!buf->base && type == EROFS_KMAP)
+		buf->base = kmap_local_page(buf->page);
 	if (type == EROFS_NO_KMAP)
 		return NULL;
 	return buf->base + (offset & ~PAGE_MASK);
@@ -352,7 +345,6 @@ static int erofs_iomap_end(struct inode *inode, loff_t pos, loff_t length,
 		struct erofs_buf buf = {
 			.page = kmap_to_page(ptr),
 			.base = ptr,
-			.kmap_type = EROFS_KMAP,
 		};
 
 		DBG_BUGON(iomap->type != IOMAP_INLINE);

fs/erofs/internal.h

@@ -212,7 +212,6 @@ struct erofs_buf {
 	struct file *file;
 	struct page *page;
 	void *base;
-	enum erofs_kmap_type kmap_type;
 };
 #define __EROFS_BUF_INITIALIZER	((struct erofs_buf){ .page = NULL })