linux-kernel - Re: [PATCH] Raise maximum number of memory controllers

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Date:   Wed, 26 Sep 2018 17:27:52 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Justin Ernst <justin.ernst@....com>, russ.anderson@....com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Raise maximum number of memory controllers

On Wed, Sep 26, 2018 at 11:35:11AM +0200, Borislav Petkov wrote:
> * or Greg coming and saying, you're using bus_type all wrong and you
> shouldn't and you should remove it completely! :-)

Yap, and so he did! :-)

It looks like we can remove the whole per-MC bus thing, see below. Patch
seems to work here and grepping sysfs hierarchy before and after:

find /sys/ | grep -i edac > ...

doesn't show any differences.

Tony, I'd appreciate running this on one of your big boxes to check
nothing is missing in sysfs...

Thx.

---
 drivers/edac/edac_mc.c       |  9 +--------
 drivers/edac/edac_mc_sysfs.c | 30 ++----------------------------
 include/linux/edac.h         |  6 ------
 3 files changed, 3 insertions(+), 42 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 7d3edd713932..13594ffadcb3 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -55,8 +55,6 @@ static LIST_HEAD(mc_devices);
  */
 static const char *edac_mc_owner;
 
-static struct bus_type mc_bus[EDAC_MAX_MCS];
-
 int edac_get_report_status(void)
 {
 	return edac_report;
@@ -716,11 +714,6 @@ int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
 	int ret = -EINVAL;
 	edac_dbg(0, "\n");
 
-	if (mci->mc_idx >= EDAC_MAX_MCS) {
-		pr_warn_once("Too many memory controllers: %d\n", mci->mc_idx);
-		return -ENODEV;
-	}
-
 #ifdef CONFIG_EDAC_DEBUG
 	if (edac_debug_level >= 3)
 		edac_mc_dump_mci(mci);
@@ -760,7 +753,7 @@ int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
 	/* set load time so that error rate can be tracked */
 	mci->start_time = jiffies;
 
-	mci->bus = &mc_bus[mci->mc_idx];
+	mci->bus = edac_get_sysfs_subsys();
 
 	if (edac_create_sysfs_mci_device(mci, groups)) {
 		edac_mc_printk(mci, KERN_WARNING,
diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 20374b8248f0..2ca2012f2857 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -914,27 +914,8 @@ static const struct device_type mci_attr_type = {
 int edac_create_sysfs_mci_device(struct mem_ctl_info *mci,
 				 const struct attribute_group **groups)
 {
-	char *name;
 	int i, err;
 
-	/*
-	 * The memory controller needs its own bus, in order to avoid
-	 * namespace conflicts at /sys/bus/edac.
-	 */
-	name = kasprintf(GFP_KERNEL, "mc%d", mci->mc_idx);
-	if (!name)
-		return -ENOMEM;
-
-	mci->bus->name = name;
-
-	edac_dbg(0, "creating bus %s\n", mci->bus->name);
-
-	err = bus_register(mci->bus);
-	if (err < 0) {
-		kfree(name);
-		return err;
-	}
-
 	/* get the /sys/devices/system/edac subsys reference */
 	mci->dev.type = &mci_attr_type;
 	device_initialize(&mci->dev);
@@ -950,7 +931,7 @@ int edac_create_sysfs_mci_device(struct mem_ctl_info *mci,
 	err = device_add(&mci->dev);
 	if (err < 0) {
 		edac_dbg(1, "failure: create device %s\n", dev_name(&mci->dev));
-		goto fail_unregister_bus;
+		goto out;
 	}
 
 	/*
@@ -998,10 +979,8 @@ int edac_create_sysfs_mci_device(struct mem_ctl_info *mci,
 		device_unregister(&dimm->dev);
 	}
 	device_unregister(&mci->dev);
-fail_unregister_bus:
-	bus_unregister(mci->bus);
-	kfree(name);
 
+out:
 	return err;
 }
 
@@ -1032,13 +1011,8 @@ void edac_remove_sysfs_mci_device(struct mem_ctl_info *mci)
 
 void edac_unregister_sysfs(struct mem_ctl_info *mci)
 {
-	struct bus_type *bus = mci->bus;
-	const char *name = mci->bus->name;
-
 	edac_dbg(1, "Unregistering device %s\n", dev_name(&mci->dev));
 	device_unregister(&mci->dev);
-	bus_unregister(bus);
-	kfree(name);
 }
 
 static void mc_attr_release(struct device *dev)
diff --git a/include/linux/edac.h b/include/linux/edac.h
index a45ce1f84bfc..dd8d006f1837 100644
--- a/include/linux/edac.h
+++ b/include/linux/edac.h
@@ -668,10 +668,4 @@ struct mem_ctl_info {
 	bool fake_inject_ue;
 	u16 fake_inject_count;
 };
-
-/*
- * Maximum number of memory controllers in the coherent fabric.
- */
-#define EDAC_MAX_MCS	16
-
 #endif
-- 
2.17.0.582.gccdcbd54c

-- 
Regards/Gruss,
    Boris.

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