btrfs: remove unused map_private_extent_buffer

All uses of map_private_extent_buffer have been replaced by more
effective way. The set/get helpers have their own bounds checker.
The function name was confusing since the non-private helper was removed
in a6591715 ("Btrfs: stop using highmem for extent_buffers") many
years ago.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -5685,48 +5685,6 @@ int read_extent_buffer_to_user(const struct extent_buffer *eb,
 	return ret;
 }
 
-/*
- * return 0 if the item is found within a page.
- * return 1 if the item spans two pages.
- * return -EINVAL otherwise.
- */
-int map_private_extent_buffer(const struct extent_buffer *eb,
-			      unsigned long start, unsigned long min_len,
-			      char **map, unsigned long *map_start,
-			      unsigned long *map_len)
-{
-	size_t offset;
-	char *kaddr;
-	struct page *p;
-	size_t start_offset = offset_in_page(eb->start);
-	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
-	unsigned long end_i = (start_offset + start + min_len - 1) >>
-		PAGE_SHIFT;
-
-	if (start + min_len > eb->len) {
-		WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, wanted %lu %lu\n",
-		       eb->start, eb->len, start, min_len);
-		return -EINVAL;
-	}
-
-	if (i != end_i)
-		return 1;
-
-	if (i == 0) {
-		offset = start_offset;
-		*map_start = 0;
-	} else {
-		offset = 0;
-		*map_start = ((u64)i << PAGE_SHIFT) - start_offset;
-	}
-
-	p = eb->pages[i];
-	kaddr = page_address(p);
-	*map = kaddr + offset;
-	*map_len = PAGE_SIZE - offset;
-	return 0;
-}
-
 int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv,
 			 unsigned long start, unsigned long len)
 {

fs/btrfs/extent_io.h

@@ -271,10 +271,6 @@ bool set_extent_buffer_dirty(struct extent_buffer *eb);
 void set_extent_buffer_uptodate(struct extent_buffer *eb);
 void clear_extent_buffer_uptodate(struct extent_buffer *eb);
 int extent_buffer_under_io(struct extent_buffer *eb);
-int map_private_extent_buffer(const struct extent_buffer *eb,
-			      unsigned long offset, unsigned long min_len,
-			      char **map, unsigned long *map_start,
-			      unsigned long *map_len);
 void extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end);
 void extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end);
 void extent_clear_unlock_delalloc(struct inode *inode, u64 start, u64 end,