f2fs: support passing down write hints to block layer with F2FS policy

Add 'whint_mode=fs-based' mount option. In this mode, F2FS passes
down write hints with its policy.

* whint_mode=fs-based. F2FS passes down hints with its policy.

User F2FS Block
---- ---- -----
META WRITE_LIFE_MEDIUM;
HOT_NODE WRITE_LIFE_NOT_SET
WARM_NODE "
COLD_NODE WRITE_LIFE_NONE
ioctl(COLD) COLD_DATA WRITE_LIFE_EXTREME
extension list " "

-- buffered io
WRITE_LIFE_EXTREME COLD_DATA WRITE_LIFE_EXTREME
WRITE_LIFE_SHORT HOT_DATA WRITE_LIFE_SHORT
WRITE_LIFE_NOT_SET WARM_DATA WRITE_LIFE_LONG
WRITE_LIFE_NONE " "
WRITE_LIFE_MEDIUM " "
WRITE_LIFE_LONG " "

-- direct io
WRITE_LIFE_EXTREME COLD_DATA WRITE_LIFE_EXTREME
WRITE_LIFE_SHORT HOT_DATA WRITE_LIFE_SHORT
WRITE_LIFE_NOT_SET WARM_DATA WRITE_LIFE_NOT_SET
WRITE_LIFE_NONE " WRITE_LIFE_NONE
WRITE_LIFE_MEDIUM " WRITE_LIFE_MEDIUM
WRITE_LIFE_LONG " WRITE_LIFE_LONG

Many thanks to Chao Yu and Jaegeuk Kim for comments to
implement this patch.

Signed-off-by: Hyunchul Lee <[e-mail]>
Reviewed-by: Chao Yu <[e-mail]>
Signed-off-by: Jaegeuk Kim <[e-mail]>

fs/f2fs/f2fs.h

···
 enum {
 	WHINT_MODE_OFF,		/* not pass down write hints */
 	WHINT_MODE_USER,	/* try to pass down hints given by users */
+	WHINT_MODE_FS,		/* pass down hints with F2FS policy */
 };
 
 struct f2fs_sb_info {

fs/f2fs/segment.c

···
  * WRITE_LIFE_MEDIUM     "                        WRITE_LIFE_MEDIUM
  * WRITE_LIFE_LONG       "                        WRITE_LIFE_LONG
  *
+ * 3) whint_mode=fs-based. F2FS passes down hints with its policy.
+ *
+ * User                  F2FS                     Block
+ * ----                  ----                     -----
+ *                       META                     WRITE_LIFE_MEDIUM;
+ *                       HOT_NODE                 WRITE_LIFE_NOT_SET
+ *                       WARM_NODE                "
+ *                       COLD_NODE                WRITE_LIFE_NONE
+ * ioctl(COLD)           COLD_DATA                WRITE_LIFE_EXTREME
+ * extension list        "                        "
+ *
+ * -- buffered io
+ * WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
+ * WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
+ * WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_LONG
+ * WRITE_LIFE_NONE       "                        "
+ * WRITE_LIFE_MEDIUM     "                        "
+ * WRITE_LIFE_LONG       "                        "
+ *
+ * -- direct io
+ * WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
+ * WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
+ * WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_NOT_SET
+ * WRITE_LIFE_NONE       "                        WRITE_LIFE_NONE
+ * WRITE_LIFE_MEDIUM     "                        WRITE_LIFE_MEDIUM
+ * WRITE_LIFE_LONG       "                        WRITE_LIFE_LONG
  */
 
 enum rw_hint io_type_to_rw_hint(struct f2fs_sb_info *sbi,
···
 {
 	if (sbi->whint_mode == WHINT_MODE_USER) {
 		if (type == DATA) {
-			switch (temp) {
-			case COLD:
-				return WRITE_LIFE_EXTREME;
-			case HOT:
-				return WRITE_LIFE_SHORT;
-			default:
+			if (temp == WARM)
 				return WRITE_LIFE_NOT_SET;
-			}
+			else if (temp == HOT)
+				return WRITE_LIFE_SHORT;
+			else if (temp == COLD)
+				return WRITE_LIFE_EXTREME;
 		} else {
 			return WRITE_LIFE_NOT_SET;
 		}
-	} else {
-		return WRITE_LIFE_NOT_SET;
+	} else if (sbi->whint_mode == WHINT_MODE_FS) {
+		if (type == DATA) {
+			if (temp == WARM)
+				return WRITE_LIFE_LONG;
+			else if (temp == HOT)
+				return WRITE_LIFE_SHORT;
+			else if (temp == COLD)
+				return WRITE_LIFE_EXTREME;
+		} else if (type == NODE) {
+			if (temp == WARM || temp == HOT)
+				return WRITE_LIFE_NOT_SET;
+			else if (temp == COLD)
+				return WRITE_LIFE_NONE;
+		} else if (type == META) {
+			return WRITE_LIFE_MEDIUM;
+		}
 	}
+	return WRITE_LIFE_NOT_SET;
 }
 
 static int __get_segment_type_2(struct f2fs_io_info *fio)

fs/f2fs/super.c

···
 			} else if (strlen(name) == 3 &&
 					!strncmp(name, "off", 3)) {
 				sbi->whint_mode = WHINT_MODE_OFF;
+			} else if (strlen(name) == 8 &&
+					!strncmp(name, "fs-based", 8)) {
+				sbi->whint_mode = WHINT_MODE_FS;
 			} else {
 				kfree(name);
 				return -EINVAL;
···
 	f2fs_show_quota_options(seq, sbi->sb);
 	if (sbi->whint_mode == WHINT_MODE_USER)
 		seq_printf(seq, ",whint_mode=%s", "user-based");
+	else if (sbi->whint_mode == WHINT_MODE_FS)
+		seq_printf(seq, ",whint_mode=%s", "fs-based");
 
 	return 0;
 }