f2fs: do not assign a new segment for dio under space shortage

If there is not enough free segment, we should not assign a new segment
explicitly. Otherwise, we can run out of free segment.

Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 7d53cb4..bf1605d 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1225,7 +1225,8 @@
 	mutex_lock(&sit_i->sentry_lock);
 
 	/* direct_io'ed data is aligned to the segment for better performance */
-	if (direct_io && curseg->next_blkoff)
+	if (direct_io && curseg->next_blkoff &&
+				!has_not_enough_free_secs(sbi, 0))
 		__allocate_new_segments(sbi, type);
 
 	*new_blkaddr = NEXT_FREE_BLKADDR(sbi, curseg);