linux-kernel - Re: [PATCH 2/9] mm: swap: factor out the actual swap entry freeing logic to new helper

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Message-ID: <a04c8908-a12a-dab8-f4e4-61f7b85443bf@huaweicloud.com>
Date: Fri, 14 Mar 2025 15:32:32 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: Kairui Song <ryncsn@...il.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/9] mm: swap: factor out the actual swap entry freeing
 logic to new helper



on 3/14/2025 1:42 AM, Kairui Song wrote:
> On Thu, Mar 13, 2025 at 8:09 PM Kemeng Shi <shikemeng@...weicloud.com> wrote:
>>
>> Factor out the actual swap entry freeing logic to new helper
>> __swap_entries_free().
>> This allow us to futher simplify other swap entry freeing code by
>> leveraging __swap_entries_free() helper function.
>>
>> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
>> ---
>>  mm/swapfile.c | 30 ++++++++++++++++++++----------
>>  1 file changed, 20 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/swapfile.c b/mm/swapfile.c
>> index 5a775456e26c..7c886f9dd6f9 100644
>> --- a/mm/swapfile.c
>> +++ b/mm/swapfile.c
>> @@ -1347,6 +1347,25 @@ static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
>>         return NULL;
>>  }
>>
>> +static inline void __swap_entries_free(struct swap_info_struct *si,
>> +                                      struct swap_cluster_info *ci,
>> +                                      swp_entry_t entry, unsigned int nr_pages)
>> +{
>> +       unsigned long offset = swp_offset(entry);
>> +
>> +       VM_BUG_ON(cluster_is_empty(ci));
>> +       VM_BUG_ON(ci->count < nr_pages);
>> +
>> +       ci->count -= nr_pages;
>> +       mem_cgroup_uncharge_swap(entry, nr_pages);
>> +       swap_range_free(si, offset, nr_pages);
>> +
>> +       if (!ci->count)
>> +               free_cluster(si, ci);
>> +       else
>> +               partial_free_cluster(si, ci);
>> +}
>> +
>>  static unsigned char swap_entry_put_locked(struct swap_info_struct *si,
>>                                            unsigned long offset,
>>                                            unsigned char usage)
>> @@ -1525,22 +1544,13 @@ static void swap_entry_range_free(struct swap_info_struct *si,
>>
>>         /* It should never free entries across different clusters */
>>         VM_BUG_ON(ci != offset_to_cluster(si, offset + nr_pages - 1));
>> -       VM_BUG_ON(cluster_is_empty(ci));
>> -       VM_BUG_ON(ci->count < nr_pages);
>>
>> -       ci->count -= nr_pages;
>>         do {
>>                 VM_BUG_ON(*map != SWAP_HAS_CACHE);
>>                 *map = 0;
>>         } while (++map < map_end);
>>
>> -       mem_cgroup_uncharge_swap(entry, nr_pages);
>> -       swap_range_free(si, offset, nr_pages);
>> -
>> -       if (!ci->count)
>> -               free_cluster(si, ci);
>> -       else
>> -               partial_free_cluster(si, ci);
>> +       __swap_entries_free(si, ci, entry, nr_pages);
>>  }
>>
>>  static void cluster_swap_free_nr(struct swap_info_struct *si,
>> --
>> 2.30.0
>>
>>
> 
> Hi Kemeng,
Hello Kairui,

Thanks for feedback.
> 
> This patch is a bit too trivial to be a standalone one, you can fold
> it with the later one easily. Also you may want to carry the
> VM_BUG_ON(ci != offset_to_cluster(si, offset + nr_pages - 1)); check
> as well.
Sure, I will do this in next version.
> 
> But, that is basically just renaming swap_entry_range_free, you may
> just remove the HAS_CACHE check as you rename it, that way the changes
> should be cleaner.
> 
Sorry, I don't quite follow. Are you suggesting that should fold this
patch to later one which removes the HAS_CACHE check and renmae the
swap_entry_range_free.

Thanks,
Kemeng