f2fs: introduce CP_TRIMMED_FLAG to avoid unneeded discard

Introduce CP_TRIMMED_FLAG to indicate all invalid block were trimmed
before umount, so once we do mount with image which contain the flag,
we don't record invalid blocks as undiscard one, when fstrim is being
triggered, we can avoid issuing redundant discard commands.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 37360b9..f0481fb 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -130,6 +130,7 @@ enum {
 #define	CP_SYNC		0x00000004
 #define	CP_RECOVERY	0x00000008
 #define	CP_DISCARD	0x00000010
+#define CP_TRIMMED	0x00000020
 
 #define DEF_BATCHED_TRIM_SECTIONS	2048
 #define BATCHED_TRIM_SEGMENTS(sbi)	\