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.
--
Cheers,
Justin (Jia He)
> -----Original Message-----
> From: gregkh@xxxxxxxxxxxxxxxxxxx <gregkh@xxxxxxxxxxxxxxxxxxx>
> Sent: Wednesday, August 19, 2020 8:29 PM
> To: Justin He <Justin.He@xxxxxxx>; Jonathan.Cameron@xxxxxxxxxx; Kaly Xin
> <Kaly.Xin@xxxxxxx>; akpm@xxxxxxxxxxxxxxxxxxxx; bhe@xxxxxxxxxx;
> bp@xxxxxxxxx; Catalin Marinas <Catalin.Marinas@xxxxxxx>; dalias@xxxxxxxx;
> dan.j.williams@xxxxxxxxx; dave.hansen@xxxxxxxxxxxxxxx;
> dave.jiang@xxxxxxxxx; david@xxxxxxxxxx; fenghua.yu@xxxxxxxxx;
> hpa@xxxxxxxxx; hslester96@xxxxxxxxx; logang@xxxxxxxxxxxx; luto@xxxxxxxxxx;
> masahiroy@xxxxxxxxxx; mhocko@xxxxxxxx; mingo@xxxxxxxxxx;
> peterz@xxxxxxxxxxxxx; rppt@xxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx;
> tglx@xxxxxxxxxxxxx; tony.luck@xxxxxxxxx; torvalds@xxxxxxxxxxxxxxxxxxxx;
> vishal.l.verma@xxxxxxxxx; will@xxxxxxxxxx; ysato@xxxxxxxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> 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 <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From b4223a510e2ab1bf0f971d50af7c1431014b25ad Mon Sep 17 00:00:00 2001
> From: Jia He <justin.he@xxxxxxx>
> 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 <justin.he@xxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>[5.6+]
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Baoquan He <bhe@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Chuhong Yuan <hslester96@xxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Cc: Kaly Xin <Kaly.Xin@xxxxxxx>
> Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Rich Felker <dalias@xxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
> Link: http://lkml.kernel.org/r/20200710031619.18762-3-justin.he@xxxxxxx
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6289a909ea36..ce3d858319bd 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -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");
> @@ -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;
> }
>
> /**
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