Re: [Crash-utility] [RFC] [PATCH 0/6] Add maple tree vma iteration support for crash
On 2022/10/12 17:44, lijiang wrote:
Hi, Tao
Thanks for the work.
On Mon, Sep 19, 2022 at 11:10 PM <crash-utility-request(a)redhat.com> wrote:
> Date: Mon, 19 Sep 2022 23:10:22 +0800
> From: Tao Liu <ltao(a)redhat.com>
> To: crash-utility(a)redhat.com
> Subject: [Crash-utility] [RFC] [PATCH 0/6] Add maple tree vma
> iteration support for crash
> Message-ID: <20220919151028.25830-1-ltao(a)redhat.com>
> Content-Type: text/plain; charset="US-ASCII"; x-default=true
>
> Patchset [1] introduces maple tree data structure for linux, and the
> modification on mm subsystem.
>
> The main impact on crash utility, is the modification on vm_area_struct.
> Patch [2][3] removed the rbtree and linked list iteration of
> vm_area_struct, making it impossible for crash to iterate vma
> in the traditional way. For example, we can observe the failing
> of crash cmd vm/fuser on kernel which has integrated with patchset [1].
>
> This patchset deals with the issue by porting and adapting
> kernel's maple tree vma iteration code to crash utility. It has been
> tested on linux-next-next-20220914 [4].
>
>
Good job. But I still have several questions about the patchset.
Can you help try to tidy up the following patches? For example:
Step 1:
- introduce the maple tree data structures and iterative algorithms as
one patch.
- (they include two files: maple_tree.c, maple_tree.h)
Patch 1: the pure copy-and-paste work, extracting related kernel
> structures, functions, constants to crash.
> Patch 2: minimal code modification for crash adaption, kernel
> structures are kept for member resolving.
> Patch 3: modification on crash memory.c to use the maple vma
> iteration.
>
> The idea is to make patch 1-3 a POC work.
>
>
Step 2:
- imitate the do_rbtree(), do_radix_tree(), do_xarray()..., you could
refer to the filesys.c/tools.c
- the maple tree can be considered as a new structure and algorithm, just
like the rbtree, radix_tree and xarray..., crash can keep the same code
style.
- the advantage is that it is easy to maintain in the future.
Agree. The kernel code of the maple tree looks quite complex to make it
minimal and crash-like, so I thought that it's ok to copy and convert it.
But it may be worth trying.
Thanks,
Kazu
>
> Step 3:
> - call the do_maple_tree(),... in crash code, etc...
> - enable the maple tree support for crash-utility
>
> That is my concern. But this may increase the difficulty of implementation,
> can you also evaluate if it is doable?
>
> Thanks.
> Lianbo
>
> Patch 4: Get rid of kernel structures by rewriting the structure
>> member resolving code into the crash way, aka change
>> "node->member" into "readmem(node) and
OFFSET(member)"
>> Patch 5: print the added variables of offset/size table
>> Patch 6: Get rid of the compiling-time assgined arrays.
>>
>> Patch 4-6 will make the POC work formal for use.
>>
>>
>> [1]:
>> https://lore.kernel.org/all/20220906194824.2110408-1-Liam.Howlett@oracle....
>> [2]:
>>
https://github.com/oracle/linux-uek/commit/d19703645b80abe35dff1a88449d07...
>> [3]:
>>
https://github.com/oracle/linux-uek/commit/91dee01f1ebb6b6587463b6ee6f7bb...
>> [4]:
>>
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/snaps...
>>
>> Tao Liu (6):
>> Port linux maple tree related files to crash
>> Maple tree kernel code modification for step 1
>> Introduce maple tree vma iteration to memory.c
>> Maple tree kernel code modification for step 2
>> Dump maple tree offset variables by help -o
>> Remove mt_slots and mt_pivots array assignment
>>
>> Makefile | 12 +-
>> defs.h | 19 ++
>> maple_tree.c | 824 +++++++++++++++++++++++++++++++++++++++++++++++
>> maple_tree.h | 109 +++++++
>> maple_tree_vma.h | 34 ++
>> memory.c | 315 ++++++++++--------
>> symbols.c | 34 ++
>> xarray.h | 70 ++++
>> 8 files changed, 1285 insertions(+), 132 deletions(-)
>> create mode 100644 maple_tree.c
>> create mode 100644 maple_tree.h
>> create mode 100644 maple_tree_vma.h
>> create mode 100644 xarray.h
>>
>> --
>> 2.33.1