linux-kernel - Re: [PATCH v5 3/5] mm: move ``get_order_from

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Message-ID: <06b96a7f-c9bb-4a65-8077-ba10e0ea1e7d@igalia.com>
Date: Mon, 4 Nov 2024 08:16:02 -0300
From: Maíra Canal <mcanal@...lia.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>,
 Hugh Dickins <hughd@...gle.com>, Barry Song <baohua@...nel.org>,
 David Hildenbrand <david@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Lance Yang <ioworker0@...il.com>
Cc: linux-mm@...ck.org, dri-devel@...ts.freedesktop.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel-dev@...lia.com
Subject: Re: [PATCH v5 3/5] mm: move ``get_order_from_str()`` to internal.h

Hi Baolin,

On 03/11/24 23:25, Baolin Wang wrote:
> 
> 
> On 2024/11/2 00:54, Maíra Canal wrote:
>> In order to implement a kernel parameter similar to ``thp_anon=`` for
>> shmem, we'll need the function ``get_order_from_str()``.
>>
>> Instead of duplicating the function, move the function to a shared
>> header, in which both mm/shmem.c and mm/huge_memory.c will be able to
>> use it.
>>
>> Signed-off-by: Maíra Canal <mcanal@...lia.com>
>> ---
>>   mm/huge_memory.c | 38 +++++++++++++++-----------------------
>>   mm/internal.h    | 22 ++++++++++++++++++++++
>>   2 files changed, 37 insertions(+), 23 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index f92068864469..a6edbd8c4f49 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -958,26 +958,6 @@ static int __init setup_transparent_hugepage(char 
>> *str)
>>   }
>>   __setup("transparent_hugepage=", setup_transparent_hugepage);
>> -static inline int get_order_from_str(const char *size_str)
>> -{
>> -    unsigned long size;
>> -    char *endptr;
>> -    int order;
>> -
>> -    size = memparse(size_str, &endptr);
>> -
>> -    if (!is_power_of_2(size))
>> -        goto err;
>> -    order = get_order(size);
>> -    if (BIT(order) & ~THP_ORDERS_ALL_ANON)
>> -        goto err;
>> -
>> -    return order;
>> -err:
>> -    pr_err("invalid size %s in thp_anon boot parameter\n", size_str);
>> -    return -EINVAL;
>> -}
>> -
>>   static char str_dup[PAGE_SIZE] __initdata;
>>   static int __init setup_thp_anon(char *str)
>>   {
>> @@ -1007,10 +987,22 @@ static int __init setup_thp_anon(char *str)
>>                   start_size = strsep(&subtoken, "-");
>>                   end_size = subtoken;
>> -                start = get_order_from_str(start_size);
>> -                end = get_order_from_str(end_size);
>> +                start = get_order_from_str(start_size, 
>> THP_ORDERS_ALL_ANON);
>> +                end = get_order_from_str(end_size, THP_ORDERS_ALL_ANON);
>>               } else {
>> -                start = end = get_order_from_str(subtoken);
>> +                start_size = end_size = subtoken;
>> +                start = end = get_order_from_str(subtoken,
>> +                                 THP_ORDERS_ALL_ANON);
>> +            }
>> +
>> +            if (start == -EINVAL) {
>> +                pr_err("invalid size %s in thp_anon boot 
>> parameter\n", start_size);
>> +                goto err;
>> +            }
>> +
>> +            if (end == -EINVAL) {
>> +                pr_err("invalid size %s in thp_anon boot 
>> parameter\n", end_size);
>> +                goto err;
>>               }
> 
> There are already checks for ‘start’ and ‘end’ below, and will print 
> error messages if error occurs. So I suspect whether these repeated 
> checks and error infor are helpful.

The idea is to explicitly show to the user which part of the kernel
parameter is broke. Instead of saying that something is broken, it is
going to return that, for example, "33K" is invalid.

Best Regards,
- Maíra

> 
> Anyway, I don't have a strong preference.
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>