Re: [PATCH v4 4/4] selftests/mm: add tests for HWPOISON hugetlbfs read

[Muhammad Usama Anjum]

On 1/11/24 7:32 AM, Sidhartha Kumar wrote:
> On 1/10/24 2:15 AM, Muhammad Usama Anjum wrote:
>> On 1/10/24 11:49 AM, Muhammad Usama Anjum wrote:
>>> On 1/6/24 2:13 AM, Jiaqi Yan wrote:
>>>> On Thu, Jan 4, 2024 at 10:27 PM Muhammad Usama Anjum
>>>> <usama.anjum@xxxxxxxxxxxxx> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> I'm trying to convert this test to TAP as I think the failures
>>>>> sometimes go
>>>>> unnoticed on CI systems if we only depend on the return value of the
>>>>> application. I've enabled the following configurations which aren't
>>>>> already
>>>>> present in tools/testing/selftests/mm/config:
>>>>> CONFIG_MEMORY_FAILURE=y
>>>>> CONFIG_HWPOISON_INJECT=m
>>>>>
>>>>> I'll send a patch to add these configs later. Right now I'm trying to
>>>>> investigate the failure when we are trying to inject the poison page by
>>>>> madvise(MADV_HWPOISON). I'm getting device busy every single time. The
>>>>> test
>>>>> fails as it doesn't expect any business for the hugetlb memory. I'm not
>>>>> sure if the poison handling code has issues or test isn't robust enough.
>>>>>
>>>>> ./hugetlb-read-hwpoison
>>>>> Write/read chunk size=0x800
>>>>>   ... HugeTLB read regression test...
>>>>>   ...  ... expect to read 0x200000 bytes of data in total
>>>>>   ...  ... actually read 0x200000 bytes of data in total
>>>>>   ... HugeTLB read regression test...TEST_PASSED
>>>>>   ... HugeTLB read HWPOISON test...
>>>>> [    9.280854] Injecting memory failure for pfn 0x102f01 at process
>>>>> virtual
>>>>> address 0x7f28ec101000
>>>>> [    9.282029] Memory failure: 0x102f01: huge page still referenced by
>>>>> 511
>>>>> users
>>>>> [    9.282987] Memory failure: 0x102f01: recovery action for huge
>>>>> page: Failed
>>>>>   ...  !!! MADV_HWPOISON failed: Device or resource busy
>>>>>   ... HugeTLB read HWPOISON test...TEST_FAILED
>>>>>
>>>>> I'm testing on v6.7-rc8. Not sure if this was working previously or not.
>>>>
>>>> Thanks for reporting this, Usama!
>>>>
>>>> I am also able to repro MADV_HWPOISON failure at "501a06fe8e4c
>>>> (akpm/mm-stable, mm-stable) zswap: memcontrol: implement zswap
>>>> writeback disabling."
>>>>
>>>> Then I checked out the earliest commit "ba91e7e5d15a (HEAD -> Base)
>>>> selftests/mm: add tests for HWPOISON hugetlbfs read". The
>>>> MADV_HWPOISON injection works and and the test passes:
>>>>
>>>>   ... HugeTLB read HWPOISON test...
>>>>   ...  ... expect to read 0x101000 bytes of data in total
>>>>   ...  !!! read failed: Input/output error
>>>>   ...  ... actually read 0x101000 bytes of data in total
>>>>   ... HugeTLB read HWPOISON test...TEST_PASSED
>>>>   ... HugeTLB seek then read HWPOISON test...
>>>>   ...  ... init val=4 with offset=0x102000
>>>>   ...  ... expect to read 0xfe000 bytes of data in total
>>>>   ...  ... actually read 0xfe000 bytes of data in total
>>>>   ... HugeTLB seek then read HWPOISON test...TEST_PASSED
>>>>   ...
>>>>
>>>> [ 2109.209225] Injecting memory failure for pfn 0x3190d01 at process
>>>> virtual address 0x7f75e3101000
>>>> [ 2109.209438] Memory failure: 0x3190d01: recovery action for huge
>>>> page: Recovered
>>>> ...
>>>>
>>>> I think something in between broken MADV_HWPOISON on hugetlbfs, and we
>>>> should be able to figure it out via bisection (and of course by
>>>> reading delta commits between them, probably related to page
>>>> refcount).
>>> Thank you for this information.
>>>
>>>>
>>>> That being said, I will be on vacation from tomorrow until the end of
>>>> next week. So I will get back to this after next weekend. Meanwhile if
>>>> you want to go ahead and bisect the problematic commit, that will be
>>>> very much appreciated.
>>> I'll try to bisect and post here if I find something.
>> Found the culprit commit by bisection:
>>
>> a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3
>> mm/filemap: remove hugetlb special casing in filemap.c
>>
>> hugetlb-read-hwpoison started failing from this patch. I've added the
>> author of this patch to this bug report.
>>
> Hi Usama,
> 
> Thanks for pointing this out. After debugging, the below diff seems to fix
> the issue and allows the tests to pass again. Could you test it on your
> configuration as well just to confirm.
> 
> Thanks,
> Sidhartha
> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 36132c9125f9..3a248e4f7e93 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -340,7 +340,7 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb,
> struct iov_iter *to)
>                 } else {
>                         folio_unlock(folio);
> 
> -                       if (!folio_test_has_hwpoisoned(folio))
> +                       if (!folio_test_hwpoison(folio))
>                                 want = nr;
>                         else {
>                                 /*
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index d8c853b35dbb..87f6bf7d8bc1 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -973,7 +973,7 @@ struct page_state {
>  static bool has_extra_refcount(struct page_state *ps, struct page *p,
>                                bool extra_pins)
>  {
> -       int count = page_count(p) - 1;
> +       int count = page_count(p) - folio_nr_pages(page_folio(p));
> 
>         if (extra_pins)
>                 count -= 1;
> 
Tested the patch, it fixes the test. Please send this patch.

Tested-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>

-- 
BR,
Muhammad Usama Anjum