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: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1508,6 +1508,118 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	return ret;
 }
 
+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;
+	int ret = 0;
+
+	block_in_file = (sector_t)page->index;
+	last_block = block_in_file + nr_pages;
+	last_block_in_file = (i_size_read(inode) + blocksize - 1) >>
+							blkbits;
+	if (last_block > last_block_in_file)
+		last_block = last_block_in_file;
+
+	/* just zeroing out page which is beyond EOF */
+	if (block_in_file >= last_block)
+		goto zero_out;
+	/*
+	 * 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))
+		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;
+
+	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;
+		SetPageMappedToDisk(page);
+
+		if (!PageUptodate(page) && !cleancache_get_page(page)) {
+			SetPageUptodate(page);
+			goto confused;
+		}
+
+		if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), block_nr,
+							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 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 ||
+		!__same_bdev(F2FS_I_SB(inode), block_nr, bio))) {
+submit_and_realloc:
+		__submit_bio(F2FS_I_SB(inode), bio, DATA);
+		bio = NULL;
+	}
+	if (bio == NULL) {
+		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 out;
+		}
+	}
+
+	/*
+	 * If the page is under writeback, we need to wait for
+	 * its completion to see the correct decrypted data.
+	 */
+	f2fs_wait_on_block_writeback(inode, block_nr);
+
+	if (bio_add_page(bio, page, blocksize, 0) < blocksize)
+		goto submit_and_realloc;
+
+	inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
+	ClearPageError(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.
@@ -1524,13 +1636,8 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 	struct bio *bio = NULL;
 	sector_t last_block_in_bio = 0;
 	struct inode *inode = mapping->host;
-	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;
+	int ret = 0;
 
 	map.m_pblk = 0;
 	map.m_lblk = 0;
@@ -1553,98 +1660,13 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 				goto next_page;
 		}
 
-		block_in_file = (sector_t)page->index;
-		last_block = block_in_file + nr_pages;
-		last_block_in_file = (i_size_read(inode) + blocksize - 1) >>
-								blkbits;
-		if (last_block > last_block_in_file)
-			last_block = last_block_in_file;
-
-		/* just zeroing out page which is beyond EOF */
-		if (block_in_file >= last_block)
-			goto zero_out;
-		/*
-		 * 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))
-			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;
-
-		if (f2fs_map_blocks(inode, &map, 0, F2FS_GET_BLOCK_DEFAULT))
-			goto set_error_page;
-got_it:
-		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)) {
-				SetPageUptodate(page);
-				goto confused;
-			}
-
-			if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), block_nr,
-								DATA_GENERIC))
-				goto set_error_page;
-		} else {
-zero_out:
+		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);
-			if (!PageUptodate(page))
-				SetPageUptodate(page);
 			unlock_page(page);
-			goto next_page;
 		}
-
-		/*
-		 * This page will go to BIO.  Do we need to send this
-		 * BIO off first?
-		 */
-		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);
-			bio = NULL;
-		}
-		if (bio == NULL) {
-			bio = f2fs_grab_read_bio(inode, block_nr, nr_pages,
-					is_readahead ? REQ_RAHEAD : 0);
-			if (IS_ERR(bio)) {
-				bio = NULL;
-				goto set_error_page;
-			}
-		}
-
-		/*
-		 * If the page is under writeback, we need to wait for
-		 * its completion to see the correct decrypted data.
-		 */
-		f2fs_wait_on_block_writeback(inode, block_nr);
-
-		if (bio_add_page(bio, page, blocksize, 0) < blocksize)
-			goto submit_and_realloc;
-
-		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;
-confused:
-		if (bio) {
-			__submit_bio(F2FS_I_SB(inode), bio, DATA);
-			bio = NULL;
-		}
-		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)