[PATCH v3 11/15] md/raid5: Refactor add_stripe_bio()

[Logan Gunthorpe]

Factor out two helper functions from add_stripe_bio(): one to check for
overlap (stripe_bio_overlaps()), and one to actually add the bio to the
stripe (__add_stripe_bio()). The latter function will always succeed.

This will be useful in the next patch so that overlap can be checked for
multiple disks before adding any

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/md/raid5.c | 86 ++++++++++++++++++++++++++++++----------------
 1 file changed, 56 insertions(+), 30 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 34f8d6c18bd3..f12773c2387a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3415,39 +3415,32 @@ schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
 		s->locked, s->ops_request);
 }
 
-/*
- * Each stripe/dev can have one or more bion attached.
- * toread/towrite point to the first in a chain.
- * The bi_next chain must be in order.
- */
-static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
-			  int forwrite, int previous)
+static bool stripe_bio_overlaps(struct stripe_head *sh, struct bio *bi,
+				int dd_idx, int forwrite)
 {
-	struct bio **bip;
 	struct r5conf *conf = sh->raid_conf;
-	int firstwrite=0;
+	struct bio **bip;
 
-	pr_debug("adding bi b#%llu to stripe s#%llu\n",
-		(unsigned long long)bi->bi_iter.bi_sector,
-		(unsigned long long)sh->sector);
+	pr_debug("checking bi b#%llu to stripe s#%llu\n",
+		 bi->bi_iter.bi_sector, sh->sector);
 
-	spin_lock_irq(&sh->stripe_lock);
 	/* Don't allow new IO added to stripes in batch list */
 	if (sh->batch_head)
-		goto overlap;
-	if (forwrite) {
+		return true;
+
+	if (forwrite)
 		bip = &sh->dev[dd_idx].towrite;
-		if (*bip == NULL)
-			firstwrite = 1;
-	} else
+	else
 		bip = &sh->dev[dd_idx].toread;
+
 	while (*bip && (*bip)->bi_iter.bi_sector < bi->bi_iter.bi_sector) {
 		if (bio_end_sector(*bip) > bi->bi_iter.bi_sector)
-			goto overlap;
-		bip = & (*bip)->bi_next;
+			return true;
+		bip = &(*bip)->bi_next;
 	}
+
 	if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
-		goto overlap;
+		return true;
 
 	if (forwrite && raid5_has_ppl(conf)) {
 		/*
@@ -3476,9 +3469,30 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 		}
 
 		if (first + conf->chunk_sectors * (count - 1) != last)
-			goto overlap;
+			return true;
 	}
 
+	return false;
+}
+
+static void __add_stripe_bio(struct stripe_head *sh, struct bio *bi,
+			     int dd_idx, int forwrite, int previous)
+{
+	struct r5conf *conf = sh->raid_conf;
+	struct bio **bip;
+	int firstwrite = 0;
+
+	if (forwrite) {
+		bip = &sh->dev[dd_idx].towrite;
+		if (!*bip)
+			firstwrite = 1;
+	} else {
+		bip = &sh->dev[dd_idx].toread;
+	}
+
+	while (*bip && (*bip)->bi_iter.bi_sector < bi->bi_iter.bi_sector)
+		bip = &(*bip)->bi_next;
+
 	if (!forwrite || previous)
 		clear_bit(STRIPE_BATCH_READY, &sh->state);
 
@@ -3505,8 +3519,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 	}
 
 	pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
-		(unsigned long long)(*bip)->bi_iter.bi_sector,
-		(unsigned long long)sh->sector, dd_idx);
+		 (*bip)->bi_iter.bi_sector, sh->sector, dd_idx);
 
 	if (conf->mddev->bitmap && firstwrite) {
 		/* Cannot hold spinlock over bitmap_startwrite,
@@ -3514,7 +3527,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 		 * we have added to the bitmap and set bm_seq.
 		 * So set STRIPE_BITMAP_PENDING to prevent
 		 * batching.
-		 * If multiple add_stripe_bio() calls race here they
+		 * If multiple __add_stripe_bio() calls race here they
 		 * much all set STRIPE_BITMAP_PENDING.  So only the first one
 		 * to complete "bitmap_startwrite" gets to set
 		 * STRIPE_BIT_DELAY.  This is important as once a stripe
@@ -3532,14 +3545,27 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 			set_bit(STRIPE_BIT_DELAY, &sh->state);
 		}
 	}
-	spin_unlock_irq(&sh->stripe_lock);
+}
 
-	return 1;
+/*
+ * Each stripe/dev can have one or more bios attached.
+ * toread/towrite point to the first in a chain.
+ * The bi_next chain must be in order.
+ */
+static bool add_stripe_bio(struct stripe_head *sh, struct bio *bi,
+			   int dd_idx, int forwrite, int previous)
+{
+	spin_lock_irq(&sh->stripe_lock);
 
- overlap:
-	set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
+	if (stripe_bio_overlaps(sh, bi, dd_idx, forwrite)) {
+		set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
+		spin_unlock_irq(&sh->stripe_lock);
+		return false;
+	}
+
+	__add_stripe_bio(sh, bi, dd_idx, forwrite, previous);
 	spin_unlock_irq(&sh->stripe_lock);
-	return 0;
+	return true;
 }
 
 static void end_reshape(struct r5conf *conf);
-- 
2.30.2