linux-kernel - [PATCH 05/26] cxl/core: Simplify cxl_dpa_set

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Date: Sun, 24 Mar 2024 16:18:08 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Dave Jiang <dave.jiang@...el.com>, Fan Ni <fan.ni@...sung.com>, 
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 Navneet Singh <navneet.singh@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>, 
 Davidlohr Bueso <dave@...olabs.net>, 
 Alison Schofield <alison.schofield@...el.com>, 
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, 
 linux-btrfs@...r.kernel.org, linux-cxl@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH 05/26] cxl/core: Simplify cxl_dpa_set_mode()

cxl_dpa_set_mode() checks the mode for validity two times, once outside
of the DPA RW semaphore and again within.  The function is not in a
critical path.  Prior to Dynamic Capacity the extra check was not much
of an issue.  The addition of DC modes increases the complexity of
the check.

Simplify the mode check before adding the more complex DC modes.

Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes for v1:
[iweiny: new patch]
[Jonathan: based on getting rid of the loop in cxl_dpa_set_mode]
[Jonathan: standardize on resource_size() == 0]
---
 drivers/cxl/core/hdm.c | 45 ++++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 7d97790b893d..66b8419fd0c3 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -411,44 +411,35 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
 	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	struct device *dev = &cxled->cxld.dev;
-	int rc;
 
+	guard(rwsem_write)(&cxl_dpa_rwsem);
+	if (cxled->cxld.flags & CXL_DECODER_F_ENABLE)
+		return -EBUSY;
+
+	/*
+	 * Check that the mode is supported by the current partition
+	 * configuration
+	 */
 	switch (mode) {
 	case CXL_DECODER_RAM:
+		if (!resource_size(&cxlds->ram_res)) {
+			dev_dbg(dev, "no available ram capacity\n");
+			return -ENXIO;
+		}
+		break;
 	case CXL_DECODER_PMEM:
+		if (!resource_size(&cxlds->pmem_res)) {
+			dev_dbg(dev, "no available pmem capacity\n");
+			return -ENXIO;
+		}
 		break;
 	default:
 		dev_dbg(dev, "unsupported mode: %d\n", mode);
 		return -EINVAL;
 	}
 
-	down_write(&cxl_dpa_rwsem);
-	if (cxled->cxld.flags & CXL_DECODER_F_ENABLE) {
-		rc = -EBUSY;
-		goto out;
-	}
-
-	/*
-	 * Only allow modes that are supported by the current partition
-	 * configuration
-	 */
-	if (mode == CXL_DECODER_PMEM && !resource_size(&cxlds->pmem_res)) {
-		dev_dbg(dev, "no available pmem capacity\n");
-		rc = -ENXIO;
-		goto out;
-	}
-	if (mode == CXL_DECODER_RAM && !resource_size(&cxlds->ram_res)) {
-		dev_dbg(dev, "no available ram capacity\n");
-		rc = -ENXIO;
-		goto out;
-	}
-
 	cxled->mode = mode;
-	rc = 0;
-out:
-	up_write(&cxl_dpa_rwsem);
-
-	return rc;
+	return 0;
 }
 
 int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)

-- 
2.44.0