Re: [PATCH 15/25] device-dax: use the dev_pagemap internal refcount

[Dan Williams <dan.j.williams@intel.com>]

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On Mon, Jun 17, 2019 at 5:28 AM Christoph Hellwig <hch@lst.de> wrote:
>
> The functionality is identical to the one currently open coded in
> device-dax.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/dax/dax-private.h |  4 ----
>  drivers/dax/device.c      | 43 ---------------------------------------
>  2 files changed, 47 deletions(-)

This needs the mock devm_memremap_pages() to setup the common
percpu_ref. Incremental patch attached:

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From 875e71489c8485448a5b7df2d8a8b2ed77d2b555 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Tue, 18 Jun 2019 11:58:24 -0700
Subject: [PATCH] tools/testing/nvdimm: Support the 'internal' ref of
 dev_pagemap

For users of the common percpu-ref implementation, like device-dax,
arrange for nfit_test to initialize the common parameters.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 tools/testing/nvdimm/test/iomap.c | 41 ++++++++++++++++++++++++-------
 1 file changed, 32 insertions(+), 9 deletions(-)

diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
index 3bc1c16c4ef9..9019dd8afbc1 100644
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -108,8 +108,6 @@ static void nfit_test_kill(void *_pgmap)
 {
 	struct dev_pagemap *pgmap = _pgmap;
 
-	WARN_ON(!pgmap || !pgmap->ref);
-
 	if (pgmap->ops && pgmap->ops->kill)
 		pgmap->ops->kill(pgmap);
 	else
@@ -123,20 +121,45 @@ static void nfit_test_kill(void *_pgmap)
 	}
 }
 
+static void dev_pagemap_percpu_release(struct percpu_ref *ref)
+{
+	struct dev_pagemap *pgmap =
+		container_of(ref, struct dev_pagemap, internal_ref);
+
+	complete(&pgmap->done);
+}
+
 void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 {
+	int error;
 	resource_size_t offset = pgmap->res.start;
 	struct nfit_test_resource *nfit_res = get_nfit_res(offset);
 
-	if (nfit_res) {
-		int rc;
+	if (!nfit_res)
+		return devm_memremap_pages(dev, pgmap);
 
-		rc = devm_add_action_or_reset(dev, nfit_test_kill, pgmap);
-		if (rc)
-			return ERR_PTR(rc);
-		return nfit_res->buf + offset - nfit_res->res.start;
+	pgmap->dev = dev;
+	if (!pgmap->ref) {
+		if (pgmap->ops && (pgmap->ops->kill || pgmap->ops->cleanup))
+			return ERR_PTR(-EINVAL);
+
+		init_completion(&pgmap->done);
+		error = percpu_ref_init(&pgmap->internal_ref,
+				dev_pagemap_percpu_release, 0, GFP_KERNEL);
+		if (error)
+			return ERR_PTR(error);
+		pgmap->ref = &pgmap->internal_ref;
+	} else {
+		if (!pgmap->ops || !pgmap->ops->kill || !pgmap->ops->cleanup) {
+			WARN(1, "Missing reference count teardown definition\n");
+			return ERR_PTR(-EINVAL);
+		}
 	}
-	return devm_memremap_pages(dev, pgmap);
+
+	error = devm_add_action_or_reset(dev, nfit_test_kill, pgmap);
+	if (error)
+		return ERR_PTR(error);
+	return nfit_res->buf + offset - nfit_res->res.start;
 }
 EXPORT_SYMBOL_GPL(__wrap_devm_memremap_pages);
 
-- 
2.20.1