On Wed, Apr 20, 2022 at 01:54:25PM -0600, Logan Gunthorpe wrote:

 struct stripe_request_ctx {
 	bool do_flush;
 	struct stripe_head *batch_last;
+	sector_t disk_sector_done;
+	sector_t start_disk_sector;

Very nitpicky, but why use two different naming styles for the sectors
here?

+	bool first_wrap;
+	sector_t last_sector;

And especially with the last_sector here a few comments explaining
what each of the sector values mean might be useful.

I'd also keep the two bool variables together for a better structure
layout.

+	 * if new_sector is less than the starting sector. Clear the
+	 * boolean once the start sector is hit for the second time.
+	 * When first_wrap is set, ignore the disk_sector_done.
+	 */
+	if (ctx->start_disk_sector == MaxSector) {
+		ctx->start_disk_sector = new_sector;
+	} else if (new_sector < ctx->start_disk_sector) {
+		ctx->first_wrap = true;
+	} else if (new_sector == ctx->start_disk_sector) {
+		ctx->first_wrap = false;
+		ctx->start_disk_sector = 0;
+		return STRIPE_SUCCESS;
+	} else if (!ctx->first_wrap && new_sector <= ctx->disk_sector_done) {
+		return STRIPE_SUCCESS;
+	}
+

I find this a bit confusing to read.  While trying to mentally untangle
it I came up with this version instead, but it could really use some
good comments explaining each of the checks as I found your big comment
to not quite match the logic easily.

	if (ctx->start_disk_sector == MaxSector) {
		/*
		 * First loop iteration, start our state machine.
		 * 
		ctx->start_disk_sector = new_sector;
	} else {
		/*
		 * We are done if we wrapped around to the same sector.
		 * (???)
		 */
		if (new_sector == ctx->start_disk_sector) {
			ctx->first_wrap = false;
			ctx->start_disk_sector = 0;
			return STRIPE_SUCCESS;
		}

		/*
		 * Sector before the start sector?  Keep going and wrap
		 * around.
		 */
		if (new_sector < ctx->start_disk_sector) {
			ctx->first_wrap = true;
		} else {
			// ???
			if (new_sector <= ctx->disk_sector_done &&
			   !ctx->first_wrap)
				return STRIPE_SUCCESS;
		}
	}