f2fs: introduce f2fs_read_single_page() for cleanup

This patch introduces f2fs_read_single_page() to wrap core operations
of reading one page in f2fs_mpage_readpages().

In addition, if we failed in f2fs_mpage_readpages(), propagate error
number to f2fs_read_data_page(), for f2fs_read_data_pages() path,
always return success.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1508,50 +1508,21 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	return ret;
 }
 
-/*
- * This function was originally taken from fs/mpage.c, and customized for f2fs.
- * Major change was from block_size == page_size in f2fs by default.
- *
- * Note that the aops->readpages() function is ONLY used for read-ahead. If
- * this function ever deviates from doing just read-ahead, it should either
- * use ->readpage() or do the necessary surgery to decouple ->readpages()
- * from read-ahead.
- */
-static int f2fs_mpage_readpages(struct address_space *mapping,
-			struct list_head *pages, struct page *page,
-			unsigned nr_pages, bool is_readahead)
-{
-	struct bio *bio = NULL;
-	sector_t last_block_in_bio = 0;
-	struct inode *inode = mapping->host;
+static int f2fs_read_single_page(struct inode *inode, struct page *page,
+					unsigned nr_pages,
+					struct f2fs_map_blocks *map,
+					struct bio **bio_ret,
+					sector_t *last_block_in_bio,
+					bool is_readahead)
+{
+	struct bio *bio = *bio_ret;
 	const unsigned blkbits = inode->i_blkbits;
 	const unsigned blocksize = 1 << blkbits;
 	sector_t block_in_file;
 	sector_t last_block;
 	sector_t last_block_in_file;
 	sector_t block_nr;
-	struct f2fs_map_blocks map;
-
-	map.m_pblk = 0;
-	map.m_lblk = 0;
-	map.m_len = 0;
-	map.m_flags = 0;
-	map.m_next_pgofs = NULL;
-	map.m_next_extent = NULL;
-	map.m_seg_type = NO_CHECK_TYPE;
-	map.m_may_create = false;
-
-	for (; nr_pages; nr_pages--) {
-		if (pages) {
-			page = list_last_entry(pages, struct page, lru);
-
-			prefetchw(&page->flags);
-			list_del(&page->lru);
-			if (add_to_page_cache_lru(page, mapping,
-						  page->index,
-						  readahead_gfp_mask(mapping)))
-				goto next_page;
-		}
+	int ret = 0;
 
 	block_in_file = (sector_t)page->index;
 	last_block = block_in_file + nr_pages;
@@ -1566,23 +1537,24 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 	/*
 	 * Map blocks using the previous result first.
 	 */
-		if ((map.m_flags & F2FS_MAP_MAPPED) &&
-				block_in_file > map.m_lblk &&
-				block_in_file < (map.m_lblk + map.m_len))
+	if ((map->m_flags & F2FS_MAP_MAPPED) &&
+			block_in_file > map->m_lblk &&
+			block_in_file < (map->m_lblk + map->m_len))
 		goto got_it;
 
 	/*
 	 * Then do more f2fs_map_blocks() calls until we are
 	 * done with this page.
 	 */
-		map.m_lblk = block_in_file;
-		map.m_len = last_block - block_in_file;
+	map->m_lblk = block_in_file;
+	map->m_len = last_block - block_in_file;
 
-		if (f2fs_map_blocks(inode, &map, 0, F2FS_GET_BLOCK_DEFAULT))
-			goto set_error_page;
+	ret = f2fs_map_blocks(inode, map, 0, F2FS_GET_BLOCK_DEFAULT);
+	if (ret)
+		goto out;
 got_it:
-		if ((map.m_flags & F2FS_MAP_MAPPED)) {
-			block_nr = map.m_pblk + block_in_file - map.m_lblk;
+	if ((map->m_flags & F2FS_MAP_MAPPED)) {
+		block_nr = map->m_pblk + block_in_file - map->m_lblk;
 		SetPageMappedToDisk(page);
 
 		if (!PageUptodate(page) && !cleancache_get_page(page)) {
@@ -1591,22 +1563,24 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 		}
 
 		if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), block_nr,
-								DATA_GENERIC))
-				goto set_error_page;
+							DATA_GENERIC)) {
+			ret = -EFAULT;
+			goto out;
+		}
 	} else {
 zero_out:
 		zero_user_segment(page, 0, PAGE_SIZE);
 		if (!PageUptodate(page))
 			SetPageUptodate(page);
 		unlock_page(page);
-			goto next_page;
+		goto out;
 	}
 
 	/*
 	 * This page will go to BIO.  Do we need to send this
 	 * BIO off first?
 	 */
-		if (bio && (last_block_in_bio != block_nr - 1 ||
+	if (bio && (*last_block_in_bio != block_nr - 1 ||
 		!__same_bdev(F2FS_I_SB(inode), block_nr, bio))) {
 submit_and_realloc:
 		__submit_bio(F2FS_I_SB(inode), bio, DATA);
@@ -1616,8 +1590,9 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 		bio = f2fs_grab_read_bio(inode, block_nr, nr_pages,
 				is_readahead ? REQ_RAHEAD : 0);
 		if (IS_ERR(bio)) {
+			ret = PTR_ERR(bio);
 			bio = NULL;
-				goto set_error_page;
+			goto out;
 		}
 	}
 
@@ -1632,19 +1607,66 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 
 	inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
 	ClearPageError(page);
-		last_block_in_bio = block_nr;
-		goto next_page;
-set_error_page:
-		SetPageError(page);
-		zero_user_segment(page, 0, PAGE_SIZE);
-		unlock_page(page);
-		goto next_page;
+	*last_block_in_bio = block_nr;
+	goto out;
 confused:
 	if (bio) {
 		__submit_bio(F2FS_I_SB(inode), bio, DATA);
 		bio = NULL;
 	}
 	unlock_page(page);
+out:
+	*bio_ret = bio;
+	return ret;
+}
+
+/*
+ * This function was originally taken from fs/mpage.c, and customized for f2fs.
+ * Major change was from block_size == page_size in f2fs by default.
+ *
+ * Note that the aops->readpages() function is ONLY used for read-ahead. If
+ * this function ever deviates from doing just read-ahead, it should either
+ * use ->readpage() or do the necessary surgery to decouple ->readpages()
+ * from read-ahead.
+ */
+static int f2fs_mpage_readpages(struct address_space *mapping,
+			struct list_head *pages, struct page *page,
+			unsigned nr_pages, bool is_readahead)
+{
+	struct bio *bio = NULL;
+	sector_t last_block_in_bio = 0;
+	struct inode *inode = mapping->host;
+	struct f2fs_map_blocks map;
+	int ret = 0;
+
+	map.m_pblk = 0;
+	map.m_lblk = 0;
+	map.m_len = 0;
+	map.m_flags = 0;
+	map.m_next_pgofs = NULL;
+	map.m_next_extent = NULL;
+	map.m_seg_type = NO_CHECK_TYPE;
+	map.m_may_create = false;
+
+	for (; nr_pages; nr_pages--) {
+		if (pages) {
+			page = list_last_entry(pages, struct page, lru);
+
+			prefetchw(&page->flags);
+			list_del(&page->lru);
+			if (add_to_page_cache_lru(page, mapping,
+						  page->index,
+						  readahead_gfp_mask(mapping)))
+				goto next_page;
+		}
+
+		ret = f2fs_read_single_page(inode, page, nr_pages, &map, &bio,
+					&last_block_in_bio, is_readahead);
+		if (ret) {
+			SetPageError(page);
+			zero_user_segment(page, 0, PAGE_SIZE);
+			unlock_page(page);
+		}
 next_page:
 		if (pages)
 			put_page(page);
@@ -1652,7 +1674,7 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 	BUG_ON(pages && !list_empty(pages));
 	if (bio)
 		__submit_bio(F2FS_I_SB(inode), bio, DATA);
-	return 0;
+	return pages ? 0 : ret;
 }
 
 static int f2fs_read_data_page(struct file *file, struct page *page)