linux-kernel - [PATCH v1 07/20] cxl/region: Add new function cxl_endpoint_get_region() to simplify cxl_add_to

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Message-ID: <20250715191143.1023512-8-rrichter@amd.com>
Date: Tue, 15 Jul 2025 21:11:30 +0200
From: Robert Richter <rrichter@....com>
To: Alison Schofield <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>, Davidlohr Bueso <dave@...olabs.net>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Gregory Price
	<gourry@...rry.net>, "Fabio M. De Francesco"
	<fabio.m.de.francesco@...ux.intel.com>, Terry Bowman <terry.bowman@....com>,
	Robert Richter <rrichter@....com>
Subject: [PATCH v1 07/20] cxl/region: Add new function cxl_endpoint_get_region() to simplify cxl_add_to_region()

Reduce complexity of cxl_add_to_region() by adding the new function
cxl_endpoint_get_region(). The function handles the creation and
construction of a region, if a region already exists, that will be
used instead.

The split in two functions helps grouping the code, simplifies the
error handlers and further reworks, and reduces both functions'
complexity and number of local variables.

Signed-off-by: Robert Richter <rrichter@....com>
---
 drivers/cxl/core/region.c | 37 ++++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 760455c760e8..57ee758bdece 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3396,7 +3396,7 @@ static int __construct_region(struct cxl_region *cxlr,
 		dev_name(&cxlr->dev), p->res, p->interleave_ways,
 		p->interleave_granularity);
 
-	/* ...to match put_device() in cxl_add_to_region() */
+	/* Pair with cxl_find_region_by_range() in cxl_endpoint_get_region(). */
 	get_device(&cxlr->dev);
 
 	return 0;
@@ -3434,13 +3434,12 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 	return cxlr;
 }
 
-int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
+static struct cxl_region *
+cxl_endpoint_get_region(struct cxl_endpoint_decoder *cxled)
 {
 	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
 	struct range *hpa = &cxled->cxld.hpa_range;
-	struct cxl_region_params *p;
-	bool attach = false;
-	int rc;
+	struct cxl_region *cxlr;
 
 	struct cxl_root_decoder *cxlrd __free(put_cxl_root_decoder) =
 		cxl_find_root_decoder(cxled);
@@ -3450,23 +3449,31 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 			"%s:%s no CXL window for range %#llx:%#llx\n",
 			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
 			hpa->start, hpa->end);
-		return -ENXIO;
+		return ERR_PTR(-ENXIO);
 	}
 
 	/*
 	 * Ensure that if multiple threads race to construct_region() for @hpa
 	 * one does the construction and the others add to that.
 	 */
-	mutex_lock(&cxlrd->range_lock);
-	struct cxl_region *cxlr __free(put_cxl_region) =
-		cxl_find_region_by_range(cxlrd, hpa);
+	guard(mutex)(&cxlrd->range_lock);
+
+	cxlr = cxl_find_region_by_range(cxlrd, hpa);
 	if (!cxlr)
-		cxlr = construct_region(cxlrd, cxled);
-	mutex_unlock(&cxlrd->range_lock);
+		return construct_region(cxlrd, cxled);
 
-	rc = PTR_ERR_OR_ZERO(cxlr);
-	if (rc)
-		return rc;
+	return cxlr;
+}
+
+int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_region *cxlr;
+	struct cxl_region_params *p;
+	bool attach = false;
+
+	cxlr = cxl_endpoint_get_region(cxled);
+	if (IS_ERR(cxlr))
+		return PTR_ERR(cxlr);
 
 	attach_target(cxlr, cxled, -1, TASK_UNINTERRUPTIBLE);
 
@@ -3486,7 +3493,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 				p->res);
 	}
 
-	return rc;
+	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_add_to_region, "CXL");
 
-- 
2.39.5