erofs: get rid of __stagingpage_alloc helper

Now open code is much cleaner due to iterative development.

Link: https://lore.kernel.org/r/20191124025217.12345-1-hsiangkao@aol.com
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>

fs/erofs/decompressor.c

@@ -73,7 +73,7 @@ static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
 			victim = availables[--top];
 			get_page(victim);
 		} else {
-			victim = erofs_allocpage(pagepool, GFP_KERNEL, false);
+			victim = erofs_allocpage(pagepool, GFP_KERNEL);
 			if (!victim)
 				return -ENOMEM;
 			victim->mapping = Z_EROFS_MAPPING_STAGING;

fs/erofs/internal.h

@@ -382,7 +382,7 @@ int erofs_namei(struct inode *dir, struct qstr *name,
 extern const struct file_operations erofs_dir_fops;
 
 /* utils.c / zdata.c */
-struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp, bool nofail);
+struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp);
 
 #if (EROFS_PCPUBUF_NR_PAGES > 0)
 void *erofs_get_pcpubuf(unsigned int pagenr);

fs/erofs/utils.c

@@ -7,7 +7,7 @@
 #include "internal.h"
 #include <linux/pagevec.h>
 
-struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp, bool nofail)
+struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
 {
 	struct page *page;
 
@@ -16,7 +16,7 @@ struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp, bool nofail)
 		DBG_BUGON(page_ref_count(page) != 1);
 		list_del(&page->lru);
 	} else {
-		page = alloc_pages(gfp | (nofail ? __GFP_NOFAIL : 0), 0);
+		page = alloc_page(gfp);
 	}
 	return page;
 }

fs/erofs/zdata.c

@@ -546,15 +546,6 @@ static bool z_erofs_collector_end(struct z_erofs_collector *clt)
 	return true;
 }
 
-static inline struct page *__stagingpage_alloc(struct list_head *pagepool,
-					       gfp_t gfp)
-{
-	struct page *page = erofs_allocpage(pagepool, gfp, true);
-
-	page->mapping = Z_EROFS_MAPPING_STAGING;
-	return page;
-}
-
 static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
 				       unsigned int cachestrategy,
 				       erofs_off_t la)
@@ -661,8 +652,9 @@ retry:
 	/* should allocate an additional staging page for pagevec */
 	if (err == -EAGAIN) {
 		struct page *const newpage =
-			__stagingpage_alloc(pagepool, GFP_NOFS);
+			erofs_allocpage(pagepool, GFP_NOFS | __GFP_NOFAIL);
 
+		newpage->mapping = Z_EROFS_MAPPING_STAGING;
 		err = z_erofs_attach_page(clt, newpage,
 					  Z_EROFS_PAGE_TYPE_EXCLUSIVE);
 		if (!err)
@@ -1079,19 +1071,24 @@ repeat:
 	unlock_page(page);
 	put_page(page);
 out_allocpage:
-	page = __stagingpage_alloc(pagepool, gfp);
+	page = erofs_allocpage(pagepool, gfp | __GFP_NOFAIL);
-	if (oldpage != cmpxchg(&pcl->compressed_pages[nr], oldpage, page)) {
+	if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
-		list_add(&page->lru, pagepool);
+		/* non-LRU / non-movable temporary page is needed */
-		cpu_relax();
-		goto repeat;
-	}
-	if (!tocache)
-		goto out;
-	if (add_to_page_cache_lru(page, mc, index + nr, gfp)) {
 		page->mapping = Z_EROFS_MAPPING_STAGING;
-		goto out;
+		tocache = false;
 	}
 
+	if (oldpage != cmpxchg(&pcl->compressed_pages[nr], oldpage, page)) {
+		if (tocache) {
+			/* since it added to managed cache successfully */
+			unlock_page(page);
+			put_page(page);
+		} else {
+			list_add(&page->lru, pagepool);
+		}
+		cond_resched();
+		goto repeat;
+	}
 	set_page_private(page, (unsigned long)pcl);
 	SetPagePrivate(page);
 out:	/* the only exit (for tracing and debugging) */