f2fs: skip encrypted inode in ASYNC IPU policy

Async request may be throttled in block layer, so page for async may keep WRITE_BACK
for a long time.

For encrytped inode, we need wait on page writeback no matter if the device supports
BDI_CAP_STABLE_WRITES. This may result in a higher waiting page writeback time for
async encrypted inode page.

This patch skips IPU for encrypted inode's updating write.
Signed-off-by: Hou Pengyang <houpengyang@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.h

@@ -593,7 +593,8 @@ static inline bool need_inplace_update(struct inode *inode,
 	 */
 	if (policy & (0x1 << F2FS_IPU_ASYNC) &&
 			fio && fio->op == REQ_OP_WRITE &&
-			!(fio->op_flags & REQ_SYNC))
+			!(fio->op_flags & REQ_SYNC) &&
+			!f2fs_encrypted_inode(inode))
 		return true;
 
 	/* this is only set during fdatasync */