From: Mike Kravetz <mike.kravetz@oracle.com>
To: Wei Yang <richard.weiyang@linux.alibaba.com>,
Baoquan He <bhe@redhat.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/10] mm/hugetlb: make sure to get NULL when list is empty
Date: Mon, 10 Aug 2020 13:28:46 -0700 [thread overview]
Message-ID: <9cf6749d-3a0a-480a-ef76-ae8cf5413a90@oracle.com> (raw)
In-Reply-To: <20200807142800.GA14692@L-31X9LVDL-1304.local>
On 8/7/20 7:28 AM, Wei Yang wrote:
> On Fri, Aug 07, 2020 at 08:49:51PM +0800, Baoquan He wrote:
>> On 08/07/20 at 05:12pm, Wei Yang wrote:
>>> list_first_entry() may not return NULL even when the list is empty.
>>>
>>> Let's make sure the behavior by using list_first_entry_or_null(),
>>> otherwise it would corrupt the list.
>>>
>>> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
>>> ---
>>> mm/hugetlb.c | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 62ec74f6d03f..0a2f3851b828 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -237,7 +237,8 @@ get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
>>> VM_BUG_ON(resv->region_cache_count <= 0);
>>
>>
>> We have had above line, is it possible to be NULL from list_first_entry?
>>
>>>
>>> resv->region_cache_count--;
>>> - nrg = list_first_entry(&resv->region_cache, struct file_region, link);
>>> + nrg = list_first_entry_or_null(&resv->region_cache,
>>> + struct file_region, link);
>>> VM_BUG_ON(!nrg);
>
> Or we can remove this VM_BUG_ON()?
>
I would prefer that we just remove the 'VM_BUG_ON(!nrg)'. Code elsewhere
is responsible for making sure there is ALWAYS an entry in the cache. That
is why the 'VM_BUG_ON(resv->region_cache_count <= 0)' is at the beginning
of the routine.
--
Mike Kravetz
next prev parent reply other threads:[~2020-08-10 20:30 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-07 9:12 [PATCH 00/10] mm/hugetlb: code refine and simplification Wei Yang
2020-08-07 9:12 ` [PATCH 01/10] mm/hugetlb: not necessary to coalesce regions recursively Wei Yang
2020-08-07 12:47 ` Baoquan He
2020-08-10 20:22 ` Mike Kravetz
2020-08-07 9:12 ` [PATCH 02/10] mm/hugetlb: make sure to get NULL when list is empty Wei Yang
2020-08-07 12:49 ` Baoquan He
2020-08-07 14:28 ` Wei Yang
2020-08-10 0:57 ` Baoquan He
2020-08-10 20:28 ` Mike Kravetz [this message]
2020-08-10 23:05 ` Wei Yang
2020-08-07 9:12 ` [PATCH 03/10] mm/hugetlb: use list_splice to merge two list at once Wei Yang
2020-08-07 12:53 ` Baoquan He
2020-08-10 21:07 ` Mike Kravetz
2020-08-07 9:12 ` [PATCH 04/10] mm/hugetlb: count file_region to be added when regions_needed != NULL Wei Yang
2020-08-07 12:54 ` Baoquan He
2020-08-10 21:46 ` Mike Kravetz
2020-08-07 9:12 ` [PATCH 05/10] mm/hugetlb: remove the redundant check on non_swap_entry() Wei Yang
2020-08-07 12:55 ` Baoquan He
2020-08-07 14:28 ` Wei Yang
2020-08-07 9:12 ` [PATCH 06/10] mm/hugetlb: remove redundant huge_pte_alloc() in hugetlb_fault() Wei Yang
2020-08-07 12:59 ` Baoquan He
2020-08-10 22:00 ` Mike Kravetz
2020-08-07 9:12 ` [PATCH 07/10] mm/hugetlb: a page from buddy is not on any list Wei Yang
2020-08-07 13:06 ` Baoquan He
2020-08-10 22:25 ` Mike Kravetz
2020-08-07 9:12 ` [PATCH 08/10] mm/hugetlb: return non-isolated page in the loop instead of break and check Wei Yang
2020-08-07 13:09 ` Baoquan He
2020-08-07 14:32 ` Wei Yang
2020-08-10 22:55 ` Mike Kravetz
2020-08-07 9:12 ` [PATCH 09/10] mm/hugetlb: narrow the hugetlb_lock protection area during preparing huge page Wei Yang
2020-08-07 13:12 ` Baoquan He
2020-08-10 23:02 ` Mike Kravetz
2020-08-07 9:12 ` [PATCH 10/10] mm/hugetlb: not necessary to abuse temporary page to workaround the nasty free_huge_page Wei Yang
2020-08-10 2:17 ` Baoquan He
2020-08-11 0:19 ` Mike Kravetz
2020-08-11 1:51 ` Baoquan He
2020-08-11 6:54 ` Michal Hocko
2020-08-11 21:43 ` Mike Kravetz
2020-08-11 23:19 ` Wei Yang
2020-08-11 23:25 ` Mike Kravetz
2020-08-12 5:40 ` Baoquan He
2020-08-13 11:46 ` Michal Hocko
2020-08-17 3:04 ` Wei Yang
2020-08-11 23:55 ` Baoquan He
2020-08-07 22:25 ` [PATCH 00/10] mm/hugetlb: code refine and simplification Mike Kravetz
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