raid5: copy write hint from origin bio to stripe

Store write hint from original bio in stripe head so it can be assigned
to bio sent to each RAID device.

Signed-off-by: Mariusz Dabrowski <mariusz.dabrowski@intel.com>
Reviewed-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Reviewed-by: Pawel Baldysiak <pawel.baldysiak@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>

drivers/md/raid5.c

@@ -1139,6 +1139,9 @@ again:
 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
 			bi->bi_io_vec[0].bv_offset = 0;
 			bi->bi_iter.bi_size = STRIPE_SIZE;
+			bi->bi_write_hint = sh->dev[i].write_hint;
+			if (!rrdev)
+				sh->dev[i].write_hint = RWF_WRITE_LIFE_NOT_SET;
 			/*
 			 * If this is discard request, set bi_vcnt 0. We don't
 			 * want to confuse SCSI because SCSI will replace payload
@@ -1190,6 +1193,8 @@ again:
 			rbi->bi_io_vec[0].bv_len = STRIPE_SIZE;
 			rbi->bi_io_vec[0].bv_offset = 0;
 			rbi->bi_iter.bi_size = STRIPE_SIZE;
+			rbi->bi_write_hint = sh->dev[i].write_hint;
+			sh->dev[i].write_hint = RWF_WRITE_LIFE_NOT_SET;
 			/*
 			 * If this is discard request, set bi_vcnt 0. We don't
 			 * want to confuse SCSI because SCSI will replace payload
@@ -3204,6 +3209,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 		(unsigned long long)sh->sector);
 
 	spin_lock_irq(&sh->stripe_lock);
+	sh->dev[dd_idx].write_hint = bi->bi_write_hint;
 	/* Don't allow new IO added to stripes in batch list */
 	if (sh->batch_head)
 		goto overlap;

drivers/md/raid5.h

@@ -257,6 +257,7 @@ struct stripe_head {
 		sector_t	sector;			/* sector of this page */
 		unsigned long	flags;
 		u32		log_checksum;
+		unsigned short	write_hint;
 	} dev[1]; /* allocated with extra space depending of RAID geometry */
 };