f2fs: reflow prepare_write_begin

Reflow prepare_write_begin so that it reads more straight forward,
and so that there is one place that does an extent cache lookup
instead of three, two of which are hidden in f2fs_get_block calls.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -3333,8 +3333,8 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
 	struct dnode_of_data dn;
 	struct page *ipage;
 	bool locked = false;
+	int flag = F2FS_GET_BLOCK_PRE_AIO;
 	int err = 0;
-	int flag;
 
 	/*
 	 * If a whole page is being written and we already preallocated all the
@@ -3344,13 +3344,12 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
 		return 0;
 
 	/* f2fs_lock_op avoids race between write CP and convert_inline_page */
-	if (f2fs_has_inline_data(inode) && pos + len > MAX_INLINE_DATA(inode))
-		flag = F2FS_GET_BLOCK_DEFAULT;
-	else
-		flag = F2FS_GET_BLOCK_PRE_AIO;
-
-	if (f2fs_has_inline_data(inode) ||
-			(pos & PAGE_MASK) >= i_size_read(inode)) {
+	if (f2fs_has_inline_data(inode)) {
+		if (pos + len > MAX_INLINE_DATA(inode))
+			flag = F2FS_GET_BLOCK_DEFAULT;
+		f2fs_map_lock(sbi, flag);
+		locked = true;
+	} else if ((pos & PAGE_MASK) >= i_size_read(inode)) {
 		f2fs_map_lock(sbi, flag);
 		locked = true;
 	}
@@ -3371,32 +3370,36 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
 			set_inode_flag(inode, FI_DATA_EXIST);
 			if (inode->i_nlink)
 				set_page_private_inline(ipage);
-		} else {
-			err = f2fs_convert_inline_page(&dn, page);
-			if (err)
-				goto out;
-			if (dn.data_blkaddr == NULL_ADDR)
-				err = f2fs_get_block(&dn, index);
+			goto out;
 		}
-	} else if (locked) {
-		err = f2fs_get_block(&dn, index);
-	} else if (!f2fs_lookup_read_extent_cache_block(inode, index,
-							&dn.data_blkaddr)) {
+		err = f2fs_convert_inline_page(&dn, page);
+		if (err || dn.data_blkaddr != NULL_ADDR)
+			goto out;
+	}
+
+	if (!f2fs_lookup_read_extent_cache_block(inode, index,
+						 &dn.data_blkaddr)) {
+		if (locked) {
+			err = f2fs_reserve_block(&dn, index);
+			goto out;
+		}
+
 		/* hole case */
 		err = f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE);
-		if (err || dn.data_blkaddr == NULL_ADDR) {
-			f2fs_put_dnode(&dn);
-			f2fs_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO);
-			WARN_ON(flag != F2FS_GET_BLOCK_PRE_AIO);
-			locked = true;
-			goto restart;
-		}
+		if (!err && dn.data_blkaddr != NULL_ADDR)
+			goto out;
+		f2fs_put_dnode(&dn);
+		f2fs_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO);
+		WARN_ON(flag != F2FS_GET_BLOCK_PRE_AIO);
+		locked = true;
+		goto restart;
 	}
-
-	/* convert_inline_page can make node_changed */
-	*blk_addr = dn.data_blkaddr;
-	*node_changed = dn.node_changed;
 out:
+	if (!err) {
+		/* convert_inline_page can make node_changed */
+		*blk_addr = dn.data_blkaddr;
+		*node_changed = dn.node_changed;
+	}
 	f2fs_put_dnode(&dn);
 unlock_out:
 	if (locked)