erofs: get rid of ->lru usage

Currently, ->lru is a way to arrange non-LRU pages and has some
in-kernel users. In order to minimize noticable issues of page
reclaim and cache thrashing under high memory presure, limited
temporary pages were all chained with ->lru and can be reused
during the request. However, it seems that ->lru could be removed
when folio is landing.

Let's use page->private to chain temporary pages for now instead
and transform EROFS formally after the topic of the folio / file
page design is finalized.

Link: https://lore.kernel.org/r/20211022090120.14675-1-hsiangkao@linux.alibaba.com
Cc: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c
index bd86067a63f7..84da2c280012 100644
--- a/fs/erofs/utils.c
+++ b/fs/erofs/utils.c
@@ -6,20 +6,29 @@
 #include "internal.h"
 #include <linux/pagevec.h>
 
-struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
+struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp)
 {
-	struct page *page;
+	struct page *page = *pagepool;
 
-	if (!list_empty(pool)) {
-		page = lru_to_page(pool);
+	if (page) {
 		DBG_BUGON(page_ref_count(page) != 1);
-		list_del(&page->lru);
+		*pagepool = (struct page *)page_private(page);
 	} else {
 		page = alloc_page(gfp);
 	}
 	return page;
 }
 
+void erofs_release_pages(struct page **pagepool)
+{
+	while (*pagepool) {
+		struct page *page = *pagepool;
+
+		*pagepool = (struct page *)page_private(page);
+		put_page(page);
+	}
+}
+
 #ifdef CONFIG_EROFS_FS_ZIP
 /* global shrink count (for all mounted EROFS instances) */
 static atomic_long_t erofs_global_shrink_cnt;