powerpc/pseries: Check memory device state before onlining/offlining

When DLPAR adding or removing memory we need to check the device
offline status before trying to online/offline the memory. This is
needed because calls device_online() and device_offline() will return
non-zero for memory that is already online and offline respectively.

This update resolves two scenarios. First, for kernel built with
auto-online memory enabled, memory will be onlined as part of calls
to add_memory(). After adding the memory the pseries dlpar code tries
to online it and fails since the memory is already online. The dlpar
code then tries to remove the memory which produces the oops message
below because the memory is not offline.

The second scenario occurs when removing memory that is already offline,
i.e. marking memory offline (via sysfs) and the trying to remove that
memory. This doesn't work because offlining the already offline memory
does not succeed and the dlpar code then fails the dlpar remove operation.

The fix for both scenarios is to check the device.offline status before
making the calls to device_online() or device_offline().

kernel BUG at mm/memory_hotplug.c:2189!
Oops: Exception in kernel mode, sig: 5 [#1]
SMP NR_CPUS=2048
NUMA
pSeries
CPU: 0 PID: 5 Comm: kworker/u129:0 Not tainted 4.12.0-rc3 torvalds#272
Workqueue: pseries hotplug workque .pseries_hp_work_fn
task: c0000003f9c89200 task.stack: c0000003f9d10000
NIP: c0000000002ca428 LR: c0000000002ca3cc CTR: c000000000ba16a0
REGS: c0000003f9d13630 TRAP: 0700   Not tainted  (4.12.0-rc3)
MSR: 800000000282b032 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI>
  CR: 22002024  XER: 0000000a
CFAR: c0000000002ca3d0 SOFTE: 1
GPR00: c0000000002ca3cc c0000003f9d138b0 c000000001bb0200 0000000000000001
GPR04: c0000003fb143c80 c0000003fef21630 0000000000000003 0000000000000002
GPR08: 0000000000000003 0000000000000003 0000000000000003 00000000000031b1
GPR12: 0000000028002042 c00000000fd80000 c000000000118ae0 c0000003fb170180
GPR16: 0000000000000000 0000000000000004 0000000000000010 c0000003ffff79c8
GPR20: c0000003ffff7b68 c0000003f728ff84 0000000000000002 0000000000000010
GPR24: 0000000000000002 c0000003f728ff80 0000000000000002 0000000000000001
GPR28: c0000003fb143c38 0000000000000002 0000000010000000 0000000020000000
NIP [c0000000002ca428] .remove_memory+0xb8/0xc0
LR [c0000000002ca3cc] .remove_memory+0x5c/0xc0
Call Trace:
[c0000003f9d138b0] [c0000000002ca3cc] .remove_memory+0x5c/0xc0 (unreliable)
[c0000003f9d13940] [c0000000000938a4] .dlpar_add_lmb+0x384/0x400
[c0000003f9d13a30] [c00000000009456c] .dlpar_memory+0x5dc/0xca0
[c0000003f9d13af0] [c00000000008ce84] .handle_dlpar_errorlog+0x74/0xe0
[c0000003f9d13b70] [c00000000008cf1c] .pseries_hp_work_fn+0x2c/0x90
[c0000003f9d13bf0] [c000000000110a5c] .process_one_work+0x17c/0x460
[c0000003f9d13c90] [c000000000110dc8] .worker_thread+0x88/0x500
[c0000003f9d13d70] [c000000000118c3c] .kthread+0x15c/0x1a0
[c0000003f9d13e30] [c00000000000ba18] .ret_from_kernel_thread+0x58/0xc0
Instruction dump:
7fe3fb78 4bd7c845 60000000 7fa3eb78 4bfdd3c9 38210090 e8010010 eba1ffe8
ebc1fff0 ebe1fff8 7c0803a6 4bfdc2ac <0fe00000> 00000000 7c0802a6 fb01ffc0

Fixes: 943db62 ("powerpc/pseries: Revert 'Auto-online hotplugged memory'")
Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>

arch/powerpc/platforms/pseries/hotplug-memory.c

@@ -336,7 +336,35 @@ static struct memory_block *lmb_to_memblock(struct of_drconf_cell *lmb)
 	return mem_block;
 }
 
+static int dlpar_change_lmb_state(struct of_drconf_cell *lmb, int online)
+{
+	struct memory_block *mem_block;
+	int rc = 0;
+
+	mem_block = lmb_to_memblock(lmb);
+	if (!mem_block)
+		return -EINVAL;
+
+	if (online && mem_block->dev.offline)
+		rc = device_online(&mem_block->dev);
+	else if (!online && !mem_block->dev.offline)
+		rc = device_offline(&mem_block->dev);
+
+	put_device(&mem_block->dev);
+	return rc;
+}
+
+static int dlpar_online_lmb(struct of_drconf_cell *lmb)
+{
+	return dlpar_change_lmb_state(lmb, 1);
+}
+
 #ifdef CONFIG_MEMORY_HOTREMOVE
+static int dlpar_offline_lmb(struct of_drconf_cell *lmb)
+{
+	return dlpar_change_lmb_state(lmb, 0);
+}
+
 static int pseries_remove_memblock(unsigned long base, unsigned int memblock_size)
 {
 	unsigned long block_sz, start_pfn;
@@ -431,19 +459,13 @@ static int dlpar_add_lmb(struct of_drconf_cell *);
 
 static int dlpar_remove_lmb(struct of_drconf_cell *lmb)
 {
-	struct memory_block *mem_block;
 	unsigned long block_sz;
 	int nid, rc;
 
 	if (!lmb_is_removable(lmb))
 		return -EINVAL;
 
-	mem_block = lmb_to_memblock(lmb);
-	if (!mem_block)
-		return -EINVAL;
-
-	rc = device_offline(&mem_block->dev);
-	put_device(&mem_block->dev);
+	rc = dlpar_offline_lmb(lmb);
 	if (rc)
 		return rc;
 
@@ -737,20 +759,6 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index,
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
-static int dlpar_online_lmb(struct of_drconf_cell *lmb)
-{
-	struct memory_block *mem_block;
-	int rc;
-
-	mem_block = lmb_to_memblock(lmb);
-	if (!mem_block)
-		return -EINVAL;
-
-	rc = device_online(&mem_block->dev);
-	put_device(&mem_block->dev);
-	return rc;
-}
-
 static int dlpar_add_lmb(struct of_drconf_cell *lmb)
 {
 	unsigned long block_sz;