f2fs: fix to read source block before invalidating it

f2fs_allocate_data_block() invalidates old block address and enable new block
address. Then, if we try to read old block by f2fs_submit_page_bio(), it will
give WARN due to reading invalid blocks.

Let's make the order sanely back.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -796,6 +796,29 @@ static int move_data_block(struct inode *inode, block_t bidx,
 	if (lfs_mode)
 		down_write(&fio.sbi->io_order_lock);
 
+	mpage = f2fs_grab_cache_page(META_MAPPING(fio.sbi),
+					fio.old_blkaddr, false);
+	if (!mpage)
+		goto up_out;
+
+	fio.encrypted_page = mpage;
+
+	/* read source block in mpage */
+	if (!PageUptodate(mpage)) {
+		err = f2fs_submit_page_bio(&fio);
+		if (err) {
+			f2fs_put_page(mpage, 1);
+			goto up_out;
+		}
+		lock_page(mpage);
+		if (unlikely(mpage->mapping != META_MAPPING(fio.sbi) ||
+						!PageUptodate(mpage))) {
+			err = -EIO;
+			f2fs_put_page(mpage, 1);
+			goto up_out;
+		}
+	}
+
 	f2fs_allocate_data_block(fio.sbi, NULL, fio.old_blkaddr, &newaddr,
 					&sum, CURSEG_COLD_DATA, NULL, false);
 
@@ -803,44 +826,18 @@ static int move_data_block(struct inode *inode, block_t bidx,
 				newaddr, FGP_LOCK | FGP_CREAT, GFP_NOFS);
 	if (!fio.encrypted_page) {
 		err = -ENOMEM;
+		f2fs_put_page(mpage, 1);
 		goto recover_block;
 	}
 
-	mpage = f2fs_pagecache_get_page(META_MAPPING(fio.sbi),
-					fio.old_blkaddr, FGP_LOCK, GFP_NOFS);
-	if (mpage) {
-		bool updated = false;
-
-		if (PageUptodate(mpage)) {
+	/* write target block */
+	f2fs_wait_on_page_writeback(fio.encrypted_page, DATA, true, true);
 	memcpy(page_address(fio.encrypted_page),
 				page_address(mpage), PAGE_SIZE);
-			updated = true;
-		}
 	f2fs_put_page(mpage, 1);
 	invalidate_mapping_pages(META_MAPPING(fio.sbi),
 				fio.old_blkaddr, fio.old_blkaddr);
-		if (updated)
-			goto write_page;
-	}
 
-	err = f2fs_submit_page_bio(&fio);
-	if (err)
-		goto put_page_out;
-
-	/* write page */
-	lock_page(fio.encrypted_page);
-
-	if (unlikely(fio.encrypted_page->mapping != META_MAPPING(fio.sbi))) {
-		err = -EIO;
-		goto put_page_out;
-	}
-	if (unlikely(!PageUptodate(fio.encrypted_page))) {
-		err = -EIO;
-		goto put_page_out;
-	}
-
-write_page:
-	f2fs_wait_on_page_writeback(fio.encrypted_page, DATA, true, true);
 	set_page_dirty(fio.encrypted_page);
 	if (clear_page_dirty_for_io(fio.encrypted_page))
 		dec_page_count(fio.sbi, F2FS_DIRTY_META);
@@ -871,11 +868,12 @@ static int move_data_block(struct inode *inode, block_t bidx,
 put_page_out:
 	f2fs_put_page(fio.encrypted_page, 1);
 recover_block:
-	if (lfs_mode)
-		up_write(&fio.sbi->io_order_lock);
 	if (err)
 		f2fs_do_replace_block(fio.sbi, &sum, newaddr, fio.old_blkaddr,
 								true, true);
+up_out:
+	if (lfs_mode)
+		up_write(&fio.sbi->io_order_lock);
 put_out:
 	f2fs_put_dnode(&dn);
 out: