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Message-ID: <20250813013240.GA78125@system.software.com>
Date: Wed, 13 Aug 2025 10:32:40 +0900
From: Byungchul Park <byungchul@...com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linuxppc-dev@...ts.ozlabs.org, virtualization@...ts.linux.dev,
linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
linux-btrfs@...r.kernel.org, jfs-discussion@...ts.sourceforge.net,
Andrew Morton <akpm@...ux-foundation.org>,
Madhavan Srinivasan <maddy@...ux.ibm.com>,
Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Jerrin Shaji George <jerrin.shaji-george@...adcom.com>,
Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
Eugenio Pérez <eperezma@...hat.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
Benjamin LaHaise <bcrl@...ck.org>, Chris Mason <clm@...com>,
Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
Muchun Song <muchun.song@...ux.dev>,
Oscar Salvador <osalvador@...e.de>,
Dave Kleikamp <shaggy@...nel.org>, Zi Yan <ziy@...dia.com>,
Matthew Brost <matthew.brost@...el.com>,
Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
Gregory Price <gourry@...rry.net>,
Ying Huang <ying.huang@...ux.alibaba.com>,
Alistair Popple <apopple@...dia.com>,
Minchan Kim <minchan@...nel.org>,
Sergey Senozhatsky <senozhatsky@...omium.org>,
kernel_team@...ynix.com
Subject: Re: [PATCH v1 2/2] treewide: remove MIGRATEPAGE_SUCCESS
On Mon, Aug 11, 2025 at 04:39:48PM +0200, David Hildenbrand wrote:
> At this point MIGRATEPAGE_SUCCESS is misnamed for all folio users,
> and now that we remove MIGRATEPAGE_UNMAP, it's really the only "success"
> return value that the code uses and expects.
>
> Let's just get rid of MIGRATEPAGE_SUCCESS completely and just use "0"
> for success.
>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
> arch/powerpc/platforms/pseries/cmm.c | 2 +-
> drivers/misc/vmw_balloon.c | 4 +--
> drivers/virtio/virtio_balloon.c | 2 +-
> fs/aio.c | 2 +-
> fs/btrfs/inode.c | 4 +--
> fs/hugetlbfs/inode.c | 4 +--
> fs/jfs/jfs_metapage.c | 8 +++---
> include/linux/migrate.h | 10 +------
> mm/migrate.c | 40 +++++++++++++---------------
> mm/migrate_device.c | 2 +-
> mm/zsmalloc.c | 4 +--
> 11 files changed, 36 insertions(+), 46 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c
> index 5e0a718d1be7b..0823fa2da1516 100644
> --- a/arch/powerpc/platforms/pseries/cmm.c
> +++ b/arch/powerpc/platforms/pseries/cmm.c
> @@ -545,7 +545,7 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
> /* balloon page list reference */
> put_page(page);
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
Yeah. The unnecessary thing has been kept. Looks better to me.
Reviewed-by: Byungchul Park <byungchul@...com>
Byungchul
> static void cmm_balloon_compaction_init(void)
> diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
> index 6653fc53c951c..6df51ee8db621 100644
> --- a/drivers/misc/vmw_balloon.c
> +++ b/drivers/misc/vmw_balloon.c
> @@ -1806,7 +1806,7 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
> * the list after acquiring the lock.
> */
> get_page(newpage);
> - ret = MIGRATEPAGE_SUCCESS;
> + ret = 0;
> }
>
> /* Update the balloon list under the @pages_lock */
> @@ -1817,7 +1817,7 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
> * If we succeed just insert it to the list and update the statistics
> * under the lock.
> */
> - if (ret == MIGRATEPAGE_SUCCESS) {
> + if (!ret) {
> balloon_page_insert(&b->b_dev_info, newpage);
> __count_vm_event(BALLOON_MIGRATE);
> }
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index e299e18346a30..eae65136cdfb5 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -875,7 +875,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
> balloon_page_finalize(page);
> put_page(page); /* balloon reference */
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
> #endif /* CONFIG_BALLOON_COMPACTION */
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 7fc7b6221312c..059e03cfa088c 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -445,7 +445,7 @@ static int aio_migrate_folio(struct address_space *mapping, struct folio *dst,
> folio_get(dst);
>
> rc = folio_migrate_mapping(mapping, dst, src, 1);
> - if (rc != MIGRATEPAGE_SUCCESS) {
> + if (rc) {
> folio_put(dst);
> goto out_unlock;
> }
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index b77dd22b8cdbe..1d64fee6f59e6 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -7411,7 +7411,7 @@ static int btrfs_migrate_folio(struct address_space *mapping,
> {
> int ret = filemap_migrate_folio(mapping, dst, src, mode);
>
> - if (ret != MIGRATEPAGE_SUCCESS)
> + if (ret)
> return ret;
>
> if (folio_test_ordered(src)) {
> @@ -7419,7 +7419,7 @@ static int btrfs_migrate_folio(struct address_space *mapping,
> folio_set_ordered(dst);
> }
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
> #else
> #define btrfs_migrate_folio NULL
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 09d4baef29cf9..34d496a2b7de6 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -1052,7 +1052,7 @@ static int hugetlbfs_migrate_folio(struct address_space *mapping,
> int rc;
>
> rc = migrate_huge_page_move_mapping(mapping, dst, src);
> - if (rc != MIGRATEPAGE_SUCCESS)
> + if (rc)
> return rc;
>
> if (hugetlb_folio_subpool(src)) {
> @@ -1063,7 +1063,7 @@ static int hugetlbfs_migrate_folio(struct address_space *mapping,
>
> folio_migrate_flags(dst, src);
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
> #else
> #define hugetlbfs_migrate_folio NULL
> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
> index b98cf3bb6c1fe..871cf4fb36366 100644
> --- a/fs/jfs/jfs_metapage.c
> +++ b/fs/jfs/jfs_metapage.c
> @@ -169,7 +169,7 @@ static int __metapage_migrate_folio(struct address_space *mapping,
> }
>
> rc = filemap_migrate_folio(mapping, dst, src, mode);
> - if (rc != MIGRATEPAGE_SUCCESS)
> + if (rc)
> return rc;
>
> for (i = 0; i < MPS_PER_PAGE; i++) {
> @@ -199,7 +199,7 @@ static int __metapage_migrate_folio(struct address_space *mapping,
> }
> }
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
> #endif /* CONFIG_MIGRATION */
>
> @@ -242,7 +242,7 @@ static int __metapage_migrate_folio(struct address_space *mapping,
> return -EAGAIN;
>
> rc = filemap_migrate_folio(mapping, dst, src, mode);
> - if (rc != MIGRATEPAGE_SUCCESS)
> + if (rc)
> return rc;
>
> if (unlikely(insert_metapage(dst, mp)))
> @@ -253,7 +253,7 @@ static int __metapage_migrate_folio(struct address_space *mapping,
> mp->folio = dst;
> remove_metapage(src, mp);
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
> #endif /* CONFIG_MIGRATION */
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 40f2b5a37efbb..02f11704fb686 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -12,13 +12,6 @@ typedef void free_folio_t(struct folio *folio, unsigned long private);
>
> struct migration_target_control;
>
> -/*
> - * Return values from addresss_space_operations.migratepage():
> - * - negative errno on page migration failure;
> - * - zero on page migration success;
> - */
> -#define MIGRATEPAGE_SUCCESS 0
> -
> /**
> * struct movable_operations - Driver page migration
> * @isolate_page:
> @@ -34,8 +27,7 @@ struct migration_target_control;
> * @src page. The driver should copy the contents of the
> * @src page to the @dst page and set up the fields of @dst page.
> * Both pages are locked.
> - * If page migration is successful, the driver should
> - * return MIGRATEPAGE_SUCCESS.
> + * If page migration is successful, the driver should return 0.
> * If the driver cannot migrate the page at the moment, it can return
> * -EAGAIN. The VM interprets this as a temporary migration failure and
> * will retry it later. Any other error value is a permanent migration
> diff --git a/mm/migrate.c b/mm/migrate.c
> index e9dacf1028dc7..2db4974178e6a 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -209,18 +209,17 @@ static void putback_movable_ops_page(struct page *page)
> * src and dst are also released by migration core. These pages will not be
> * folios in the future, so that must be reworked.
> *
> - * Returns MIGRATEPAGE_SUCCESS on success, otherwise a negative error
> - * code.
> + * Returns 0 on success, otherwise a negative error code.
> */
> static int migrate_movable_ops_page(struct page *dst, struct page *src,
> enum migrate_mode mode)
> {
> - int rc = MIGRATEPAGE_SUCCESS;
> + int rc;
>
> VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(src), src);
> VM_WARN_ON_ONCE_PAGE(!PageMovableOpsIsolated(src), src);
> rc = page_movable_ops(src)->migrate_page(dst, src, mode);
> - if (rc == MIGRATEPAGE_SUCCESS)
> + if (!rc)
> ClearPageMovableOpsIsolated(src);
> return rc;
> }
> @@ -565,7 +564,7 @@ static int __folio_migrate_mapping(struct address_space *mapping,
> if (folio_test_swapbacked(folio))
> __folio_set_swapbacked(newfolio);
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
>
> oldzone = folio_zone(folio);
> @@ -666,7 +665,7 @@ static int __folio_migrate_mapping(struct address_space *mapping,
> }
> local_irq_enable();
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
>
> int folio_migrate_mapping(struct address_space *mapping,
> @@ -715,7 +714,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
>
> xas_unlock_irq(&xas);
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
>
> /*
> @@ -831,14 +830,14 @@ static int __migrate_folio(struct address_space *mapping, struct folio *dst,
> return rc;
>
> rc = __folio_migrate_mapping(mapping, dst, src, expected_count);
> - if (rc != MIGRATEPAGE_SUCCESS)
> + if (rc)
> return rc;
>
> if (src_private)
> folio_attach_private(dst, folio_detach_private(src));
>
> folio_migrate_flags(dst, src);
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
>
> /**
> @@ -945,7 +944,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
> }
>
> rc = filemap_migrate_folio(mapping, dst, src, mode);
> - if (rc != MIGRATEPAGE_SUCCESS)
> + if (rc)
> goto unlock_buffers;
>
> bh = head;
> @@ -1049,7 +1048,7 @@ static int fallback_migrate_folio(struct address_space *mapping,
> *
> * Return value:
> * < 0 - error code
> - * MIGRATEPAGE_SUCCESS - success
> + * 0 - success
> */
> static int move_to_new_folio(struct folio *dst, struct folio *src,
> enum migrate_mode mode)
> @@ -1077,7 +1076,7 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
> else
> rc = fallback_migrate_folio(mapping, dst, src, mode);
>
> - if (rc == MIGRATEPAGE_SUCCESS) {
> + if (!rc) {
> /*
> * For pagecache folios, src->mapping must be cleared before src
> * is freed. Anonymous folios must stay anonymous until freed.
> @@ -1427,7 +1426,7 @@ static int unmap_and_move_huge_page(new_folio_t get_new_folio,
> if (folio_ref_count(src) == 1) {
> /* page was freed from under us. So we are done. */
> folio_putback_hugetlb(src);
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
>
> dst = get_new_folio(src, private);
> @@ -1490,8 +1489,7 @@ static int unmap_and_move_huge_page(new_folio_t get_new_folio,
> rc = move_to_new_folio(dst, src, mode);
>
> if (page_was_mapped)
> - remove_migration_ptes(src,
> - rc == MIGRATEPAGE_SUCCESS ? dst : src, 0);
> + remove_migration_ptes(src, !rc ? dst : src, 0);
>
> unlock_put_anon:
> folio_unlock(dst);
> @@ -1500,7 +1498,7 @@ static int unmap_and_move_huge_page(new_folio_t get_new_folio,
> if (anon_vma)
> put_anon_vma(anon_vma);
>
> - if (rc == MIGRATEPAGE_SUCCESS) {
> + if (!rc) {
> move_hugetlb_state(src, dst, reason);
> put_new_folio = NULL;
> }
> @@ -1508,7 +1506,7 @@ static int unmap_and_move_huge_page(new_folio_t get_new_folio,
> out_unlock:
> folio_unlock(src);
> out:
> - if (rc == MIGRATEPAGE_SUCCESS)
> + if (!rc)
> folio_putback_hugetlb(src);
> else if (rc != -EAGAIN)
> list_move_tail(&src->lru, ret);
> @@ -1618,7 +1616,7 @@ static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio,
> reason, ret_folios);
> /*
> * The rules are:
> - * Success: hugetlb folio will be put back
> + * 0: hugetlb folio will be put back
> * -EAGAIN: stay on the from list
> * -ENOMEM: stay on the from list
> * Other errno: put on ret_folios list
> @@ -1635,7 +1633,7 @@ static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio,
> retry++;
> nr_retry_pages += nr_pages;
> break;
> - case MIGRATEPAGE_SUCCESS:
> + case 0:
> stats->nr_succeeded += nr_pages;
> break;
> default:
> @@ -1689,7 +1687,7 @@ static void migrate_folios_move(struct list_head *src_folios,
> reason, ret_folios);
> /*
> * The rules are:
> - * Success: folio will be freed
> + * 0: folio will be freed
> * -EAGAIN: stay on the unmap_folios list
> * Other errno: put on ret_folios list
> */
> @@ -1699,7 +1697,7 @@ static void migrate_folios_move(struct list_head *src_folios,
> *thp_retry += is_thp;
> *nr_retry_pages += nr_pages;
> break;
> - case MIGRATEPAGE_SUCCESS:
> + case 0:
> stats->nr_succeeded += nr_pages;
> stats->nr_thp_succeeded += is_thp;
> break;
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index e05e14d6eacdb..abd9f6850db65 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -778,7 +778,7 @@ static void __migrate_device_pages(unsigned long *src_pfns,
> if (migrate && migrate->fault_page == page)
> extra_cnt = 1;
> r = folio_migrate_mapping(mapping, newfolio, folio, extra_cnt);
> - if (r != MIGRATEPAGE_SUCCESS)
> + if (r)
> src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
> else
> folio_migrate_flags(newfolio, folio);
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 2c5e56a653544..84eb91d47a226 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -1746,7 +1746,7 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
> * instead.
> */
> if (!zpdesc->zspage)
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
>
> /* The page is locked, so this pointer must remain valid */
> zspage = get_zspage(zpdesc);
> @@ -1813,7 +1813,7 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
> reset_zpdesc(zpdesc);
> zpdesc_put(zpdesc);
>
> - return MIGRATEPAGE_SUCCESS;
> + return 0;
> }
>
> static void zs_page_putback(struct page *page)
> --
> 2.50.1
>
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