FAILED: patch "[PATCH] mm/memory_hotplug: fix unpaired mem_hotplug_begin/done" failed to apply to 4.19-stable tree

-----Original Message-----
From: [email protected] <[email protected]>
Sent: Wednesday, August 19, 2020 8:29 PM
To: Justin He <[email protected]>; [email protected]; Kaly Xin <[email protected]>; [email protected]; [email protected]; [email protected]; Catalin Marinas <[email protected]>; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Cc: [email protected]
Subject: FAILED: patch "[PATCH] mm/memory_hotplug: fix unpaired mem_hotplug_begin/done" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b4223a510e2ab1bf0f971d50af7c1431014b25ad Mon Sep 17 00:00:00 2001
From: Jia He <[email protected]>
Date: Tue, 11 Aug 2020 18:32:20 -0700
Subject: [PATCH] mm/memory_hotplug: fix unpaired mem_hotplug_begin/done

When check_memblock_offlined_cb() returns failed rc(e.g. the memblock is online at that time), mem_hotplug_begin/done is unpaired in such case.

Therefore a warning:

 Call Trace:
  percpu_up_write+0x33/0x40
  try_remove_memory+0x66/0x120
  ? _cond_resched+0x19/0x30
  remove_memory+0x2b/0x40
  dev_dax_kmem_remove+0x36/0x72 [kmem]
  device_release_driver_internal+0xf0/0x1c0
  device_release_driver+0x12/0x20
  bus_remove_device+0xe1/0x150
  device_del+0x17b/0x3e0
  unregister_dev_dax+0x29/0x60
  devm_action_release+0x15/0x20
  release_nodes+0x19a/0x1e0
  devres_release_all+0x3f/0x50
  device_release_driver_internal+0x100/0x1c0
  driver_detach+0x4c/0x8f
  bus_remove_driver+0x5c/0xd0
  driver_unregister+0x31/0x50
  dax_pmem_exit+0x10/0xfe0 [dax_pmem]

Fixes f1037ec0cc8a ("mm/memory_hotplug: fix remove_memory() lockdep

splat")

Signed-off-by Jia He <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Reviewed-by David Hildenbrand <[email protected]>

Acked-by Michal Hocko <[email protected]>

Acked-by Dan Williams <[email protected]>

Cc <[email protected]>[5.6+]

Cc Andy Lutomirski <[email protected]>

Cc Baoquan He <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Catalin Marinas <[email protected]>

Cc Chuhong Yuan <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Dave Jiang <[email protected]>

Cc Fenghua Yu <[email protected]>

Cc "H. Peter Anvin" <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc Jonathan Cameron <[email protected]>

Cc Kaly Xin <[email protected]>

Cc Logan Gunthorpe <[email protected]>

Cc Masahiro Yamada <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Peter Zijlstra <[email protected]>

Cc Rich Felker <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Tony Luck <[email protected]>

Cc Vishal Verma <[email protected]>

Cc Will Deacon <[email protected]>

Cc Yoshinori Sato <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Linus Torvalds <[email protected]>

mm/memory_hotplug.c +1 -1

index 6289a909ea36..ce3d858319bd 100644
@@ -1757,7 +1757,7 @@ static int __ref try_remove_memory(int nid, u64
 start, u64 size)
  */
 rc = walk_memory_blocks(start, size, NULL,
 check_memblock_offlined_cb);
 if (rc)
-goto done;
+return rc;
 

/* remove memmap entry */ firmware_map_remove(start, start + size, "System RAM");

mm/memory_hotplug.c +1 -2

@@ -1781,9 +1781,8 @@ static int __ref try_remove_memory(int nid, u64
 start, u64 size)
 
 try_offline_node(nid);
 
-done:
 mem_hotplug_done();
-return rc;
+return 0;
 }
 

/**

Hi Greg,
If anybody wants to backport it to stable tree, there are 2 pre-condition for this commit ("[PATCH] mm/memory_hotplug: fix unpaired mem_hotplug_begin/done")

1. eca499ab3 ("mm/hotplug: make remove_memory() interface usable") applied in v5.2, it disabled the BUG() when check_memblock_offlined_cb() failed.
2. f1037ec0c ("mm/memory_hotplug: fix remove_memory() lockdep splat") in v5.5, it introduced the unpair but depends on eca499ab3

I checked https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/memory_hotplug.c?h=linux-4.19.y#n1913.
Looks like stable tree v4.19 hasn't applied eca499ab3 but applied f1037ec0c.
Hence I don't think v4.19 needs this patch.