[PATCH RFC 3/4] btrfs: introduce dedicated helper to scrub simple-stripe based range

[Qu Wenruo <wqu@suse.com>]

The new entrance will iterate through each data stripe which belongs to
the target device.

And since inside each data stripe, RAID0 is just SINGLE, while RAID10 is
just RAID1, we can reuse scrub_simple_mirror() to do the scrub properly.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/scrub.c | 60 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 57 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index ddd069bd2375..aff9db6fbc7e 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -3446,6 +3446,55 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
 	return ret;
 }
 
+static int scrub_simple_stripe(struct scrub_ctx *sctx,
+				struct btrfs_root *extent_root,
+				struct btrfs_root *csum_root,
+				struct btrfs_block_group *bg,
+				struct map_lookup *map,
+				struct btrfs_device *device,
+				int stripe_index)
+{
+	/* The increment of logical bytenr */
+	const u64 logical_increment = (map->num_stripes / map->sub_stripes) *
+				      map->stripe_len;
+	/*
+	 * Our starting logical bytenr needs to be calculated based on
+	 * stripe_index.
+	 *
+	 * stripe_index / sub_stripes gives how many data stripes we need to
+	 * skip.
+	 */
+	const u64 orig_logical = (stripe_index / map->sub_stripes) *
+				 map->stripe_len + bg->start;
+	const u64 orig_physical = map->stripes[stripe_index].physical;
+	/*
+	 * For RAID0, it's fixed to 1.
+	 * For RAID10, the mirror_num is always 0,1,0,1,...
+	 */
+	const int mirror_num = stripe_index % map->sub_stripes + 1;
+	u64 cur_logical = orig_logical;
+	u64 cur_physical = orig_physical;
+	int ret = 0;
+
+	while (cur_logical < bg->start + bg->length) {
+		/*
+		 * Inside each stripe, RAID0 is just SINGLE, and RAID10 is
+		 * just RAID1, so we can reuse scrub_simple_mirror() to scrub
+		 * this stripe.
+		 */
+		ret = scrub_simple_mirror(sctx, extent_root, csum_root, bg, map,
+					  cur_logical, map->stripe_len, device,
+					  cur_physical, mirror_num);
+		if (ret)
+			return ret;
+		/* Skip to next stripe which belongs to the target device */
+		cur_logical += logical_increment;
+		/* For physical offset, we just go to next stripe */
+		cur_physical += map->stripe_len;
+	}
+	return ret;
+}
+
 static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 					   struct btrfs_block_group *bg,
 					   struct map_lookup *map,
@@ -3576,9 +3625,14 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 				stripe_index + 1);
 		goto out;
 	}
-	/*
-	 * now find all extents for each stripe and scrub them
-	 */
+	if (profile & (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID10)) {
+		ret = scrub_simple_stripe(sctx, root, csum_root, bg, map,
+					  scrub_dev, stripe_index);
+		goto out;
+	}
+
+	/* Only RAID56 goes through the old code */
+	ASSERT(map->type & BTRFS_BLOCK_GROUP_RAID56_MASK);
 	ret = 0;
 	while (physical < physical_end) {
 		/*
-- 
2.34.1