linux-kernel - [PATCH v1 6/8] md/raid5: Refactor add_stripe

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Date:   Thu,  7 Apr 2022 10:45:09 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        Song Liu <song@...nel.org>
Cc:     Shaohua Li <shli@...nel.org>,
        Guoqing Jiang <guoqing.jiang@...ux.dev>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <Martin.Oliveira@...eticom.com>,
        David Sloan <David.Sloan@...eticom.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v1 6/8] md/raid5: Refactor add_stripe_bio()

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@...tatee.com>
---
 drivers/md/raid5.c | 79 ++++++++++++++++++++++++++++++----------------
 1 file changed, 52 insertions(+), 27 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b852b6439898..52227dd91e89 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3371,39 +3371,33 @@ 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 int 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",
+		 (unsigned long long)bi->bi_iter.bi_sector,
+		 (unsigned long long)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 1;
+
+	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;
+			return 1;
 		bip = & (*bip)->bi_next;
 	}
+
 	if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
-		goto overlap;
+		return 1;
 
 	if (forwrite && raid5_has_ppl(conf)) {
 		/*
@@ -3432,7 +3426,25 @@ 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 1;
+	}
+
+	return 0;
+}
+
+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;
 	}
 
 	if (!forwrite || previous)
@@ -3470,7 +3482,7 @@ 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
@@ -3488,14 +3500,27 @@ 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 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)
+{
+	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 0;
+	}
+
+	__add_stripe_bio(sh, bi, dd_idx, forwrite, previous);
 	spin_unlock_irq(&sh->stripe_lock);
-	return 0;
+	return 1;
 }
 
 static void end_reshape(struct r5conf *conf);
-- 
2.30.2