linux-kernel - [Patch v4 5/7] acpi_memhotplug.c: don't allow to eject the memory device if it is being used

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Message-Id: <1352372693-32411-6-git-send-email-wency@cn.fujitsu.com>
Date:	Thu, 8 Nov 2012 19:04:51 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-acpi@...r.kernel.org, Len Brown <len.brown@...el.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Toshi Kani <toshi.kani@...com>,
	Wen Congyang <wency@...fujitsu.com>,
	Jiang Liu <liuj97@...il.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Christoph Lameter <cl@...ux.com>
Subject: [Patch v4 5/7] acpi_memhotplug.c: don't allow to eject the memory device if it is being used

We eject the memory device even if it is in use.  It is very dangerous,
and it will cause the kernel to be panicked.

CC: David Rientjes <rientjes@...gle.com>
CC: Jiang Liu <liuj97@...il.com>
CC: Len Brown <len.brown@...el.com>
CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC: Paul Mackerras <paulus@...ba.org>
CC: Christoph Lameter <cl@...ux.com>
Cc: Minchan Kim <minchan.kim@...il.com>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
CC: Rafael J. Wysocki <rjw@...k.pl>
CC: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Wen Congyang <wency@...fujitsu.com>
---
 drivers/acpi/acpi_memhotplug.c | 46 +++++++++++++++++++++++++++++++++---------
 1 file changed, 36 insertions(+), 10 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 8914399..1fb1342 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -78,6 +78,7 @@ struct acpi_memory_info {
 	unsigned short caching;	/* memory cache attribute */
 	unsigned short write_protect;	/* memory read/write attribute */
 	unsigned int enabled:1;
+	unsigned int failed:1;
 };
 
 struct acpi_memory_device {
@@ -266,9 +267,23 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 			node = memory_add_physaddr_to_nid(info->start_addr);
 
 		result = add_memory(node, info->start_addr, info->length);
-		if (result)
+
+		/*
+		 * If the memory block has been used by the kernel, add_memory()
+		 * returns -EEXIST. If add_memory() returns the other error, it
+		 * means that this memory block is not used by the kernel.
+		 */
+		if (result && result != -EEXIST) {
+			info->failed = 1;
 			continue;
-		info->enabled = 1;
+		}
+
+		if (!result)
+			info->enabled = 1;
+		/*
+		 * Add num_enable even if add_memory() returns -EEXIST, so the
+		 * device is bound to this driver.
+		 */
 		num_enabled++;
 	}
 	mutex_unlock(&mem_device->list_lock);
@@ -324,25 +339,36 @@ static int acpi_memory_powerdown_device(struct acpi_memory_device *mem_device)
 
 static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
 {
-	int result;
+	int result = 0;
 	struct acpi_memory_info *info, *n;
 
 	mutex_lock(&mem_device->list_lock);
 	list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
-		if (info->enabled) {
-			result = remove_memory(info->start_addr, info->length);
-			if (result) {
-				mutex_unlock(&mem_device->list_lock);
-				return result;
-			}
+		if (info->failed)
+			/* The kernel does not use this memory block */
+			continue;
+
+		if (!info->enabled) {
+			/*
+			 * The kernel uses this memory block, but it may be not
+			 * managed by us.
+			 */
+			result = -EBUSY;
+			goto out;
 		}
 
+		result = remove_memory(info->start_addr, info->length);
+		if (result)
+			goto out;
+
 		list_del(&info->list);
 		kfree(info);
 	}
+
+out:
 	mutex_unlock(&mem_device->list_lock);
 
-	return 0;
+	return result;
 }
 
 static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
-- 
1.8.0

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