Merge tag 'erofs-for-5.16-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

Pull erofs fixes from Gao Xiang:

 - fix unsafe pagevec reuse which could cause unexpected behaviors

 - get rid of the unused DELAYEDALLOC strategy that has been replaced by
   TRYALLOC

* tag 'erofs-for-5.16-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: remove useless cache strategy of DELAYEDALLOC
  erofs: fix unsafe pagevec reuse of hooked pclusters

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)
@@ -371,8 +360,8 @@ static bool z_erofs_try_inplace_io(struct z_erofs_collector *clt,
 
 /* callers must be with collection lock held */
 static int z_erofs_attach_page(struct z_erofs_collector *clt,
-			       struct page *page,
-			       enum z_erofs_page_type type)
+			       struct page *page, enum z_erofs_page_type type,
+			       bool pvec_safereuse)
 {
 	int ret;
 
@@ -382,9 +371,9 @@ static int z_erofs_attach_page(struct z_erofs_collector *clt,
 	    z_erofs_try_inplace_io(clt, page))
 		return 0;
 
-	ret = z_erofs_pagevec_enqueue(&clt->vector, page, type);
+	ret = z_erofs_pagevec_enqueue(&clt->vector, page, type,
+				      pvec_safereuse);
 	clt->cl->vcnt += (unsigned int)ret;
-
 	return ret ? 0 : -EAGAIN;
 }
 
@@ -727,7 +716,8 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 		tight &= (clt->mode >= COLLECT_PRIMARY_FOLLOWED);
 
 retry:
-	err = z_erofs_attach_page(clt, page, page_type);
+	err = z_erofs_attach_page(clt, page, page_type,
+				  clt->mode >= COLLECT_PRIMARY_FOLLOWED);
 	/* should allocate an additional short-lived page for pagevec */
 	if (err == -EAGAIN) {
 		struct page *const newpage =
@@ -735,7 +725,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 
 		set_page_private(newpage, Z_EROFS_SHORTLIVED_PAGE);
 		err = z_erofs_attach_page(clt, newpage,
-					  Z_EROFS_PAGE_TYPE_EXCLUSIVE);
+					  Z_EROFS_PAGE_TYPE_EXCLUSIVE, true);
 		if (!err)
 			goto retry;
 	}
@@ -1089,15 +1079,6 @@ 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

@@ -179,4 +179,3 @@ static inline void z_erofs_onlinepage_endio(struct page *page)
 #define Z_EROFS_VMAP_GLOBAL_PAGES	2048
 
 #endif
-

fs/erofs/zpvec.h

@@ -106,11 +106,18 @@ static inline void z_erofs_pagevec_ctor_init(struct z_erofs_pagevec_ctor *ctor,
 
 static inline bool z_erofs_pagevec_enqueue(struct z_erofs_pagevec_ctor *ctor,
 					   struct page *page,
-					   enum z_erofs_page_type type)
+					   enum z_erofs_page_type type,
+					   bool pvec_safereuse)
 {
-	if (!ctor->next && type)
-		if (ctor->index + 1 == ctor->nr)
+	if (!ctor->next) {
+		/* some pages cannot be reused as pvec safely without I/O */
+		if (type == Z_EROFS_PAGE_TYPE_EXCLUSIVE && !pvec_safereuse)
+			type = Z_EROFS_VLE_PAGE_TYPE_TAIL_SHARED;
+
+		if (type != Z_EROFS_PAGE_TYPE_EXCLUSIVE &&
+		    ctor->index + 1 == ctor->nr)
 			return false;
+	}
 
 	if (ctor->index >= ctor->nr)
 		z_erofs_pagevec_ctor_pagedown(ctor, false);