Merge tag 'erofs-for-5.11-rc1' of git://git.kernel.org/pub/scm/linux/…

…kernel/git/xiang/erofs

Pull erofs updates from Gao Xiang:
 "This cycle we got rid of magical page->mapping type marks for
  temporary pages which had some concern before, now such usage is
  replaced with specific page->private.

  Also switch to inplace I/O instead of allocating extra cached pages to
  avoid direct reclaim under low memory scenario.

  There are some bmap bugfix and minor cleanups as well"

* tag 'erofs-for-5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: avoid using generic_block_bmap
  erofs: force inplace I/O under low memory scenario
  erofs: simplify try_to_claim_pcluster()
  erofs: insert to managed cache after adding to pcl
  erofs: get rid of magical Z_EROFS_MAPPING_STAGING
  erofs: remove a void EROFS_VERSION macro set in Makefile

fs/erofs/Makefile

@@ -1,11 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
-EROFS_VERSION = "1.0"
-
-ccflags-y += -DEROFS_VERSION=\"$(EROFS_VERSION)\"
-
 obj-$(CONFIG_EROFS_FS) += erofs.o
 erofs-objs := super.o inode.o data.o namei.o dir.o utils.o
 erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
 erofs-$(CONFIG_EROFS_FS_ZIP) += decompressor.o zmap.o zdata.o
-

fs/erofs/compress.h

@@ -26,30 +26,58 @@ struct z_erofs_decompress_req {
 	bool inplace_io, partial_decoding;
 };
 
+/* some special page->private (unsigned long, see below) */
+#define Z_EROFS_SHORTLIVED_PAGE		(-1UL << 2)
+#define Z_EROFS_PREALLOCATED_PAGE	(-2UL << 2)
+
 /*
- * - 0x5A110C8D ('sallocated', Z_EROFS_MAPPING_STAGING) -
- * used to mark temporary allocated pages from other
- * file/cached pages and NULL mapping pages.
+ * For all pages in a pcluster, page->private should be one of
+ * Type                         Last 2bits      page->private
+ * short-lived page             00              Z_EROFS_SHORTLIVED_PAGE
+ * preallocated page (tryalloc) 00              Z_EROFS_PREALLOCATED_PAGE
+ * cached/managed page          00              pointer to z_erofs_pcluster
+ * online page (file-backed,    01/10/11        sub-index << 2 | count
+ *              some pages can be used for inplace I/O)
+ *
+ * page->mapping should be one of
+ * Type                 page->mapping
+ * short-lived page     NULL
+ * preallocated page    NULL
+ * cached/managed page  non-NULL or NULL (invalidated/truncated page)
+ * online page          non-NULL
+ *
+ * For all managed pages, PG_private should be set with 1 extra refcount,
+ * which is used for page reclaim / migration.
  */
-#define Z_EROFS_MAPPING_STAGING         ((void *)0x5A110C8D)
 
-/* check if a page is marked as staging */
-static inline bool z_erofs_page_is_staging(struct page *page)
+/*
+ * short-lived pages are pages directly from buddy system with specific
+ * page->private (no need to set PagePrivate since these are non-LRU /
+ * non-movable pages and bypass reclaim / migration code).
+ */
+static inline bool z_erofs_is_shortlived_page(struct page *page)
 {
-	return page->mapping == Z_EROFS_MAPPING_STAGING;
+	if (page->private != Z_EROFS_SHORTLIVED_PAGE)
+		return false;
+
+	DBG_BUGON(page->mapping);
+	return true;
 }
 
-static inline bool z_erofs_put_stagingpage(struct list_head *pagepool,
-					   struct page *page)
+static inline bool z_erofs_put_shortlivedpage(struct list_head *pagepool,
+					      struct page *page)
 {
-	if (!z_erofs_page_is_staging(page))
+	if (!z_erofs_is_shortlived_page(page))
 		return false;
 
-	/* staging pages should not be used by others at the same time */
-	if (page_ref_count(page) > 1)
+	/* short-lived pages should not be used by others at the same time */
+	if (page_ref_count(page) > 1) {
 		put_page(page);
-	else
+	} else {
+		/* follow the pcluster rule above. */
+		set_page_private(page, 0);
 		list_add(&page->lru, pagepool);
+	}
 	return true;
 }
 

fs/erofs/data.c

@@ -312,27 +312,12 @@ static void erofs_raw_access_readahead(struct readahead_control *rac)
 		submit_bio(bio);
 }
 
-static int erofs_get_block(struct inode *inode, sector_t iblock,
-			   struct buffer_head *bh, int create)
-{
-	struct erofs_map_blocks map = {
-		.m_la = iblock << 9,
-	};
-	int err;
-
-	err = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
-	if (err)
-		return err;
-
-	if (map.m_flags & EROFS_MAP_MAPPED)
-		bh->b_blocknr = erofs_blknr(map.m_pa);
-
-	return err;
-}
-
 static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
 {
 	struct inode *inode = mapping->host;
+	struct erofs_map_blocks map = {
+		.m_la = blknr_to_addr(block),
+	};
 
 	if (EROFS_I(inode)->datalayout == EROFS_INODE_FLAT_INLINE) {
 		erofs_blk_t blks = i_size_read(inode) >> LOG_BLOCK_SIZE;
@@ -341,7 +326,10 @@ static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
 			return 0;
 	}
 
-	return generic_block_bmap(mapping, block, erofs_get_block);
+	if (!erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW))
+		return erofs_blknr(map.m_pa);
+
+	return 0;
 }
 
 /* for uncompressed (aligned) files and raw access for other files */

fs/erofs/decompressor.c

@@ -76,7 +76,7 @@ static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
 			victim = erofs_allocpage(pagepool, GFP_KERNEL);
 			if (!victim)
 				return -ENOMEM;
-			victim->mapping = Z_EROFS_MAPPING_STAGING;
+			set_page_private(victim, Z_EROFS_SHORTLIVED_PAGE);
 		}
 		rq->out[i] = victim;
 	}