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@google.com>
CC: Jiang Liu <redacted>
CC: Len Brown <redacted>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <redacted>
CC: Christoph Lameter <redacted>
Cc: Minchan Kim <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <redacted>
CC: Yasuaki Ishimatsu <redacted>
CC: Rafael J. Wysocki <redacted>
CC: Konrad Rzeszutek Wilk <redacted>
Signed-off-by: Wen Congyang <redacted>
---
 drivers/acpi/acpi_memhotplug.c | 42 +++++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index e52ad5d..f7e3007 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 {

@@ -257,9 +258,23 @@ 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++;
        }
        if (!num_enabled) {

@@ -280,21 +295,30 @@ static int acpi_memory_enable_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;

        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);
        }

-       return 0;
+       return result;
 }

 static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
--

1.8.0

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