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Date: Wed, 08 May 2024 15:56:33 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Ryan Roberts <ryan.roberts@....com>, Barry Song <21cnbao@...il.com>
Cc: <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
<baolin.wang@...ux.alibaba.com>, <chrisl@...nel.org>,
<david@...hat.com>, <hanchuanhua@...o.com>, <hannes@...xchg.org>,
<hughd@...gle.com>, <kasong@...cent.com>,
<linux-kernel@...r.kernel.org>, <surenb@...gle.com>,
<v-songbaohua@...o.com>, <willy@...radead.org>, <xiang@...nel.org>,
<yosryahmed@...gle.com>, <yuzhao@...gle.com>, <ziy@...dia.com>,
"Rafael J. Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@....cz>,
Len Brown <len.brown@...el.com>
Subject: Re: [PATCH v3 2/6] mm: remove swap_free() and always use
swap_free_nr()
Ryan Roberts <ryan.roberts@....com> writes:
> On 03/05/2024 01:50, Barry Song wrote:
>> From: Barry Song <v-songbaohua@...o.com>
>>
>> To streamline maintenance efforts, we propose discontinuing the use of
>> swap_free(). Instead, we can simply invoke swap_free_nr() with nr set
>> to 1. This adjustment offers the advantage of enabling batch processing
>> within kernel/power/swap.c. Furthermore, swap_free_nr() is designed with
>> a bitmap consisting of only one long, resulting in overhead that can be
>> ignored for cases where nr equals 1.
>>
>> Suggested-by: "Huang, Ying" <ying.huang@...el.com>
>> Signed-off-by: Barry Song <v-songbaohua@...o.com>
>> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
>> Cc: Pavel Machek <pavel@....cz>
>> Cc: Len Brown <len.brown@...el.com>
>> Cc: Hugh Dickins <hughd@...gle.com>
>> ---
>> include/linux/swap.h | 5 -----
>> kernel/power/swap.c | 7 +++----
>> mm/memory.c | 2 +-
>> mm/rmap.c | 4 ++--
>> mm/shmem.c | 4 ++--
>> mm/swapfile.c | 19 +++++--------------
>> 6 files changed, 13 insertions(+), 28 deletions(-)
>>
>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>> index d1d35e92d7e9..f03cb446124e 100644
>> --- a/include/linux/swap.h
>> +++ b/include/linux/swap.h
>> @@ -482,7 +482,6 @@ extern int add_swap_count_continuation(swp_entry_t, gfp_t);
>> extern void swap_shmem_alloc(swp_entry_t);
>> extern int swap_duplicate(swp_entry_t);
>> extern int swapcache_prepare(swp_entry_t);
>> -extern void swap_free(swp_entry_t);
>
> I wonder if it would be cleaner to:
>
> #define swap_free(entry) swap_free_nr((entry), 1)
>
> To save all the churn for the callsites that just want to pass a single entry?
I prefer this way. Although I prefer inline functions.
Otherwise, LGTM. Feel free to add
Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
in the future version.
>> extern void swap_free_nr(swp_entry_t entry, int nr_pages);
>> extern void swapcache_free_entries(swp_entry_t *entries, int n);
>> extern void free_swap_and_cache_nr(swp_entry_t entry, int nr);
>> @@ -561,10 +560,6 @@ static inline int swapcache_prepare(swp_entry_t swp)
>> return 0;
>> }
>>
>> -static inline void swap_free(swp_entry_t swp)
>> -{
>> -}
>> -
>> static inline void swap_free_nr(swp_entry_t entry, int nr_pages)
>> {
>> }
>> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
>> index 5bc04bfe2db1..6befaa88a342 100644
>> --- a/kernel/power/swap.c
>> +++ b/kernel/power/swap.c
>> @@ -181,7 +181,7 @@ sector_t alloc_swapdev_block(int swap)
>> offset = swp_offset(get_swap_page_of_type(swap));
>> if (offset) {
>> if (swsusp_extents_insert(offset))
>> - swap_free(swp_entry(swap, offset));
>> + swap_free_nr(swp_entry(swap, offset), 1);
>> else
>> return swapdev_block(swap, offset);
>> }
>> @@ -200,12 +200,11 @@ void free_all_swap_pages(int swap)
>>
>> while ((node = swsusp_extents.rb_node)) {
>> struct swsusp_extent *ext;
>> - unsigned long offset;
>>
>> ext = rb_entry(node, struct swsusp_extent, node);
>> rb_erase(node, &swsusp_extents);
>> - for (offset = ext->start; offset <= ext->end; offset++)
>> - swap_free(swp_entry(swap, offset));
>> + swap_free_nr(swp_entry(swap, ext->start),
>> + ext->end - ext->start + 1);
>>
>> kfree(ext);
>> }
>> diff --git a/mm/memory.c b/mm/memory.c
>> index eea6e4984eae..f033eb3528ba 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -4225,7 +4225,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>> * We're already holding a reference on the page but haven't mapped it
>> * yet.
>> */
>> - swap_free(entry);
>> + swap_free_nr(entry, 1);
>> if (should_try_to_free_swap(folio, vma, vmf->flags))
>> folio_free_swap(folio);
>>
>> diff --git a/mm/rmap.c b/mm/rmap.c
>> index 087a79f1f611..39ec7742acec 100644
>> --- a/mm/rmap.c
>> +++ b/mm/rmap.c
>> @@ -1865,7 +1865,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>> goto walk_done_err;
>> }
>> if (arch_unmap_one(mm, vma, address, pteval) < 0) {
>> - swap_free(entry);
>> + swap_free_nr(entry, 1);
>> set_pte_at(mm, address, pvmw.pte, pteval);
>> goto walk_done_err;
>> }
>> @@ -1873,7 +1873,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>> /* See folio_try_share_anon_rmap(): clear PTE first. */
>> if (anon_exclusive &&
>> folio_try_share_anon_rmap_pte(folio, subpage)) {
>> - swap_free(entry);
>> + swap_free_nr(entry, 1);
>> set_pte_at(mm, address, pvmw.pte, pteval);
>> goto walk_done_err;
>> }
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index fa2a0ed97507..bfc8a2beb24f 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -1836,7 +1836,7 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
>> * in shmem_evict_inode().
>> */
>> shmem_recalc_inode(inode, -1, -1);
>> - swap_free(swap);
>> + swap_free_nr(swap, 1);
>> }
>>
>> /*
>> @@ -1927,7 +1927,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
>>
>> delete_from_swap_cache(folio);
>> folio_mark_dirty(folio);
>> - swap_free(swap);
>> + swap_free_nr(swap, 1);
>> put_swap_device(si);
>>
>> *foliop = folio;
>> diff --git a/mm/swapfile.c b/mm/swapfile.c
>> index ec12f2b9d229..ddcd0f24b9a1 100644
>> --- a/mm/swapfile.c
>> +++ b/mm/swapfile.c
>> @@ -1343,19 +1343,6 @@ static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
>> swap_range_free(p, offset, 1);
>> }
>>
>> -/*
>> - * Caller has made sure that the swap device corresponding to entry
>> - * is still around or has not been recycled.
>> - */
>> -void swap_free(swp_entry_t entry)
>> -{
>> - struct swap_info_struct *p;
>> -
>> - p = _swap_info_get(entry);
>> - if (p)
>> - __swap_entry_free(p, entry);
>> -}
>> -
>> static void cluster_swap_free_nr(struct swap_info_struct *sis,
>> unsigned long offset, int nr_pages)
>> {
>> @@ -1385,6 +1372,10 @@ static void cluster_swap_free_nr(struct swap_info_struct *sis,
>> unlock_cluster_or_swap_info(sis, ci);
>> }
>>
>> +/*
>> + * Caller has made sure that the swap device corresponding to entry
>> + * is still around or has not been recycled.
>> + */
>> void swap_free_nr(swp_entry_t entry, int nr_pages)
>> {
>> int nr;
>> @@ -1930,7 +1921,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
>> new_pte = pte_mkuffd_wp(new_pte);
>> setpte:
>> set_pte_at(vma->vm_mm, addr, pte, new_pte);
>> - swap_free(entry);
>> + swap_free_nr(entry, 1);
>> out:
>> if (pte)
>> pte_unmap_unlock(pte, ptl);
--
Best Regards,
Huang, Ying
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