Btrfs: fill ->last_trans for delayed inode in btrfs_fill_inode.

We need to fill inode when we found a node for it in delayed_nodes_tree.
But we did not fill the ->last_trans currently, it will cause the test
of xfstest/generic/311 fail. Scenario of the 311 is shown as below:

Problem:
	(1). test_fd = open(fname, O_RDWR|O_DIRECT)
	(2). pwrite(test_fd, buf, 4096, 0)
	(3). close(test_fd)
	(4). drop_all_caches()	<-------- "echo 3 > /proc/sys/vm/drop_caches"
	(5). test_fd = open(fname, O_RDWR|O_DIRECT)
	(6). fsync(test_fd);
				<-------- we did not get the correct log entry for the file
Reason:
	When we re-open this file in (5), we would find a node
in delayed_nodes_tree and fill the inode we are lookup with the
information. But the ->last_trans is not filled, then the fsync()
will check the ->last_trans and found it's 0 then say this inode
is already in our tree which is commited, not recording the extents
for it.

Fix:
	This patch fill the ->last_trans properly and set the
runtime_flags if needed in this situation. Then we can get the
log entries we expected after (6) and generic/311 passed.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Reviewed-by: Miao Xie <miaoxie@huawei.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/delayed-inode.c

@@ -1802,6 +1802,8 @@ int btrfs_fill_inode(struct inode *inode, u32 *rdev)
 	set_nlink(inode, btrfs_stack_inode_nlink(inode_item));
 	inode_set_bytes(inode, btrfs_stack_inode_nbytes(inode_item));
 	BTRFS_I(inode)->generation = btrfs_stack_inode_generation(inode_item);
+        BTRFS_I(inode)->last_trans = btrfs_stack_inode_transid(inode_item);
+
 	inode->i_version = btrfs_stack_inode_sequence(inode_item);
 	inode->i_rdev = 0;
 	*rdev = btrfs_stack_inode_rdev(inode_item);

fs/btrfs/inode.c

@@ -3633,16 +3633,6 @@ static void btrfs_read_locked_inode(struct inode *inode)
 	BTRFS_I(inode)->generation = btrfs_inode_generation(leaf, inode_item);
 	BTRFS_I(inode)->last_trans = btrfs_inode_transid(leaf, inode_item);
 
-	/*
-	 * If we were modified in the current generation and evicted from memory
-	 * and then re-read we need to do a full sync since we don't have any
-	 * idea about which extents were modified before we were evicted from
-	 * cache.
-	 */
-	if (BTRFS_I(inode)->last_trans == root->fs_info->generation)
-		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
-			&BTRFS_I(inode)->runtime_flags);
-
 	inode->i_version = btrfs_inode_sequence(leaf, inode_item);
 	inode->i_generation = BTRFS_I(inode)->generation;
 	inode->i_rdev = 0;
@@ -3652,6 +3642,19 @@ static void btrfs_read_locked_inode(struct inode *inode)
 	BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);
 
 cache_index:
+	/*
+	 * If we were modified in the current generation and evicted from memory
+	 * and then re-read we need to do a full sync since we don't have any
+	 * idea about which extents were modified before we were evicted from
+	 * cache.
+	 *
+	 * This is required for both inode re-read from disk and delayed inode
+	 * in delayed_nodes_tree.
+	 */
+	if (BTRFS_I(inode)->last_trans == root->fs_info->generation)
+		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+			&BTRFS_I(inode)->runtime_flags);
+
 	path->slots[0]++;
 	if (inode->i_nlink != 1 ||
 	    path->slots[0] >= btrfs_header_nritems(leaf))