Re: [BUG BISECT] bug mm/vmalloc.c:470 (mm/vmalloc.c: get rid of one single unlink_va() when merge)

[Uladzislau Rezki]

Hello, Krzysztof.

On Mon, Jun 03, 2019 at 11:07:46AM +0200, Krzysztof Kozlowski wrote:
> Hi,
> 
> On recent next I see bugs during boot (after bringing up user-space or
> during reboot):
> kernel BUG at ../mm/vmalloc.c:470!
> On all my boards. On QEMU I see something similar, although the
> message is "Internal error: Oops - undefined instruction: 0 [#1] ARM",
> 
> The calltrace is:
> [   34.565126] [<c0275c9c>] (__free_vmap_area) from [<c0276044>]
> (__purge_vmap_area_lazy+0xd0/0x170)
> [   34.573963] [<c0276044>] (__purge_vmap_area_lazy) from [<c0276d50>]
> (_vm_unmap_aliases+0x1fc/0x244)
> [   34.582974] [<c0276d50>] (_vm_unmap_aliases) from [<c0279500>]
> (__vunmap+0x170/0x200)
> [   34.590770] [<c0279500>] (__vunmap) from [<c01d5a70>]
> (do_free_init+0x40/0x5c)
> [   34.597955] [<c01d5a70>] (do_free_init) from [<c01478f4>]
> (process_one_work+0x228/0x810)
> [   34.606018] [<c01478f4>] (process_one_work) from [<c0147f0c>]
> (worker_thread+0x30/0x570)
> [   34.614077] [<c0147f0c>] (worker_thread) from [<c014e8b4>]
> (kthread+0x134/0x164)
> [   34.621438] [<c014e8b4>] (kthread) from [<c01010b4>]
> (ret_from_fork+0x14/0x20)
> 
> Full log here:
> https://krzk.eu/#/builders/1/builds/3356/steps/14/logs/serial0
> https://krzk.eu/#/builders/22/builds/1118/steps/35/logs/serial0
> 
> Bisect pointed to:
> 728e0fbf263e3ed359c10cb13623390564102881 is the first bad commit
> commit 728e0fbf263e3ed359c10cb13623390564102881
> Author: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> Date:   Sat Jun 1 12:20:19 2019 +1000
>     mm/vmalloc.c: get rid of one single unlink_va() when merge
> 
I have checked the linux-next. I can confirm it happens because of:
 mm/vmalloc.c: get rid of one single unlink_va() when merge

The problem is that, it has been applied wrongly into linux-next tree
for some reason, i do not why. Probably due to the fact that i based
my work on 5.1/2-rcX, whereas linux-next is a bit ahead of it. If so,
sorry for that.

See below the clean patch for remotes/linux-next/master:

<snip>
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 650c89f38c1e..0ed95b864e31 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -719,9 +719,6 @@ merge_or_add_vmap_area(struct vmap_area *va,
                        /* Check and update the tree if needed. */
                        augment_tree_propagate_from(sibling);

-                       /* Remove this VA, it has been merged. */
-                       unlink_va(va, root);
-
                        /* Free vmap_area object. */
                        kmem_cache_free(vmap_area_cachep, va);

@@ -746,12 +743,11 @@ merge_or_add_vmap_area(struct vmap_area *va,
                        /* Check and update the tree if needed. */
                        augment_tree_propagate_from(sibling);

-                       /* Remove this VA, it has been merged. */
-                       unlink_va(va, root);
+                       if (merged)
+                               unlink_va(va, root);

                        /* Free vmap_area object. */
                        kmem_cache_free(vmap_area_cachep, va);
-
                        return;
                }
        }
-- 
2.11.0
<snip>

Andrew, i am not sure how to proceed with that. Should i send an updated series
based on linux-next tip or you can fix directly that patch?

Thank you!

--
Vlad Rezki