erofs: remove unneeded parameter

After commit 0615090c ("erofs: convert compressed files from
readpages to readahead"), add_to_page_cache_lru() was moved to mm
code, so that in below call path, no page will be cached into
@pagepool list or grabbed from @pagepool list:
- z_erofs_readpage
 - z_erofs_do_read_page
  - preload_compressed_pages
  - erofs_allocpage

Let's get rid of this unneeded @pagepool parameter.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20200917011821.22767-1-yuchao0@huawei.comReviewed-by: NGao Xiang <hsiangkao@redhat.com>
Signed-off-by: NGao Xiang <hsiangkao@redhat.com>

fs/erofs/zdata.c

@@ -153,8 +153,7 @@ static DEFINE_MUTEX(z_pagemap_global_lock);
 
 static void preload_compressed_pages(struct z_erofs_collector *clt,
 				     struct address_space *mc,
-				     enum z_erofs_cache_alloctype type,
-				     struct list_head *pagepool)
+				     enum z_erofs_cache_alloctype type)
 {
 	const struct z_erofs_pcluster *pcl = clt->pcl;
 	const unsigned int clusterpages = BIT(pcl->clusterbits);
@@ -562,8 +561,7 @@ static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
 }
 
 static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
-				struct page *page,
-				struct list_head *pagepool)
+				struct page *page)
 {
 	struct inode *const inode = fe->inode;
 	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
@@ -620,8 +618,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 	else
 		cache_strategy = DONTALLOC;
 
-	preload_compressed_pages(clt, MNGD_MAPPING(sbi),
-				 cache_strategy, pagepool);
+	preload_compressed_pages(clt, MNGD_MAPPING(sbi), cache_strategy);
 
 hitted:
 	/*
@@ -653,7 +650,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 	/* should allocate an additional staging page for pagevec */
 	if (err == -EAGAIN) {
 		struct page *const newpage =
-			erofs_allocpage(pagepool, GFP_NOFS | __GFP_NOFAIL);
+				alloc_page(GFP_NOFS | __GFP_NOFAIL);
 
 		newpage->mapping = Z_EROFS_MAPPING_STAGING;
 		err = z_erofs_attach_page(clt, newpage,
@@ -1282,7 +1279,7 @@ static int z_erofs_readpage(struct file *file, struct page *page)
 
 	f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
 
-	err = z_erofs_do_read_page(&f, page, &pagepool);
+	err = z_erofs_do_read_page(&f, page);
 	(void)z_erofs_collector_end(&f.clt);
 
 	/* if some compressed cluster ready, need submit them anyway */
@@ -1341,7 +1338,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
 		/* traversal in reverse order */
 		head = (void *)page_private(page);
 
-		err = z_erofs_do_read_page(&f, page, &pagepool);
+		err = z_erofs_do_read_page(&f, page);
 		if (err)
 			erofs_err(inode->i_sb,
 				  "readahead error at page %lu @ nid %llu",