[PATCH V2] megaraid: kmemleak: Track page allocation for fusion

[shuwang@redhat.com]

From: Shu Wang <shuwang@redhat.com>

Kmemleak reports about a thousand false positives for fusion->
cmd_list[]. Root casue is the cmd_list objects are allocated from
slab allocator, and stored its pointer in object allocated by page
allocator. The fix will tell kmemleak to track and scan fusion
object.

V2:
Add comment, balance braces, move kmemleak_free before free_pages.
checkpatch passed.

Before patch:
kmemleak: 1004 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

unreferenced object 0xffff88042584e000 (size 8192):
  backtrace:
     kmemleak_alloc+0x4a/0xa0
     __kmalloc+0xec/0x220
     megasas_alloc_cmdlist_fusion+0x3e/0x140 [megaraid_sas]
     megasas_alloc_cmds_fusion+0x44/0x450 [megaraid_sas]
     megasas_init_adapter_fusion+0x21d/0x6e0 [megaraid_sas]
     megasas_init_fw+0x357/0xd30 [megaraid_sas]
     megasas_probe_one.part.34+0x5be/0x1040 [megaraid_sas]
     megasas_probe_one+0x46/0xc0 [megaraid_sas]
     local_pci_probe+0x45/0xa0
     work_for_cpu_fn+0x14/0x20
     process_one_work+0x149/0x360
     worker_thread+0x1d8/0x3c0
     kthread+0x109/0x140
     ret_from_fork+0x25/0x30

Signed-off-by: Shu Wang <shuwang@redhat.com>
---
 drivers/scsi/megaraid/megaraid_sas_fusion.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c
index 11bd2e698b84..161b8e5518c0 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
@@ -48,6 +48,7 @@
 #include <linux/mutex.h>
 #include <linux/poll.h>
 #include <linux/vmalloc.h>
+#include <linux/kmemleak.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -4512,6 +4513,13 @@ megasas_alloc_fusion_context(struct megasas_instance *instance)
 			dev_err(&instance->pdev->dev, "Failed from %s %d\n", __func__, __LINE__);
 			return -ENOMEM;
 		}
+	} else {
+		/*
+		 * Allow kmemleak to scan these pages as they contain pointers
+		 * to additional allocations. fusion->cmd_list[].
+		 */
+		kmemleak_alloc(instance->ctrl_context,
+			sizeof(struct fusion_context), 1, GFP_KERNEL);
 	}
 
 	fusion = instance->ctrl_context;
@@ -4548,9 +4556,11 @@ megasas_free_fusion_context(struct megasas_instance *instance)
 
 		if (is_vmalloc_addr(fusion))
 			vfree(fusion);
-		else
+		else {
+			kmemleak_free(fusion);
 			free_pages((ulong)fusion,
 				instance->ctrl_context_pages);
+		}
 	}
 }
 
-- 
2.13.5