linux-kernel - [PATCH 4/8] donot allow to eject the memory device if it is being used

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Date:	Tue, 26 Jun 2012 17:20:44 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	lenb@...nel.org, linux-acpi@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Yasuaki ISIMATU <isimatu.yasuaki@...fujitsu.com>
Subject: [PATCH 4/8] donot 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 panicked.

Signed-off-by: Wen Congyang <wency@...fujitsu.com>
---
 drivers/acpi/acpi_memhotplug.c |   34 +++++++++++++++++++++++++++-------
 1 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index a325bb9..2e5d5ab 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 {
@@ -251,9 +252,19 @@ 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;
 		num_enabled++;
 	}
 	if (!num_enabled) {
@@ -317,11 +328,20 @@ static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
 	 * Note: Assume that this function returns zero on success
 	 */
 	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)
-				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.
+			 */
+			return -EBUSY;
+
+		result = remove_memory(info->start_addr, info->length);
+		if (result)
+			return result;
 		list_del(&info->list);
 		kfree(info);
 	}
-- 
1.7.1

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