erofs: remove useless cache strategy of DELAYEDALLOC

After commit 1825c8d7 ("erofs: force inplace I/O under low
memory scenario") and TRYALLOC is widely used, DELAYEDALLOC won't
be used anymore. Remove related dead code. Also, remove the blank
line at the end of zdata.h.

Link: https://lore.kernel.org/r/20211106082315.25781-1-huyue2@yulong.comReviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Yue Hu <huyue2@yulong.com>
Signed-off-by: Gao Xiang <xiang@kernel.org>

fs/erofs/zdata.c

@@ -96,16 +96,9 @@ static void z_erofs_free_pcluster(struct z_erofs_pcluster *pcl)
 	DBG_BUGON(1);
 }
 
-/*
- * a compressed_pages[] placeholder in order to avoid
- * being filled with file pages for in-place decompression.
- */
-#define PAGE_UNALLOCATED     ((void *)0x5F0E4B1D)
-
 /* how to allocate cached pages for a pcluster */
 enum z_erofs_cache_alloctype {
 	DONTALLOC,	/* don't allocate any cached pages */
-	DELAYEDALLOC,	/* delayed allocation (at the time of submitting io) */
 	/*
 	 * try to use cached I/O if page allocation succeeds or fallback
 	 * to in-place I/O instead to avoid any direct reclaim.
@@ -267,10 +260,6 @@ static void preload_compressed_pages(struct z_erofs_collector *clt,
 			/* I/O is needed, no possible to decompress directly */
 			standalone = false;
 			switch (type) {
-			case DELAYEDALLOC:
-				t = tagptr_init(compressed_page_t,
-						PAGE_UNALLOCATED);
-				break;
 			case TRYALLOC:
 				newpage = erofs_allocpage(pagepool, gfp);
 				if (!newpage)
@@ -1092,15 +1081,6 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
 	if (!page)
 		goto out_allocpage;
 
-	/*
-	 * the cached page has not been allocated and
-	 * an placeholder is out there, prepare it now.
-	 */
-	if (page == PAGE_UNALLOCATED) {
-		tocache = true;
-		goto out_allocpage;
-	}
-
 	/* process the target tagged pointer */
 	t = tagptr_init(compressed_page_t, page);
 	justfound = tagptr_unfold_tags(t);

fs/erofs/zdata.h

@@ -186,4 +186,3 @@ static inline void z_erofs_onlinepage_endio(struct page *page)
 #define Z_EROFS_VMAP_GLOBAL_PAGES	2048
 
 #endif
-