From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0354717E4 for ; Sat, 6 Sep 2025 00:27:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757118438; cv=none; b=L5Za+fqXRBE7ozht2wJj/+80fz35y1wAXUsIcEeTIwKT6Yzk+4ZWrZgcSvgpCUduStEzaOjGSrdhB6JVwkUOE5f1OE4OWVtD5BG0JKFkMvc79jSlj6KHEnHq0uLoDFsSyqz16uom4fuuj21VHWhkCrAEnxe5KigD0pGQuq6qhVc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757118438; c=relaxed/simple; bh=lRUwFwPCQ2aocRqkXmlDH/QGRXZScvYFj+px3ahS3nY=; h=Date:To:From:Subject:Message-Id; b=YOcepMbAhewoaQmcFXMoktAdEQM4XLzs28iHHVO/UuyIzCfk4onXO4IN/zXYilMBqXAvzK0J+cIi4B2qXfCKiztHgCdhUZ2Uw889BkHYiHtq8BRyI+lf2YOFx3pVSzQw1KsvCDnTrq9E/NOIN1rK5NXKajU1KrTcS5SmTv+8iVA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Bdm/C5vq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Bdm/C5vq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C3EBAC4CEF1; Sat, 6 Sep 2025 00:27:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1757118437; bh=lRUwFwPCQ2aocRqkXmlDH/QGRXZScvYFj+px3ahS3nY=; h=Date:To:From:Subject:From; b=Bdm/C5vqF9PPjc1e+IMQ8ElkXfJ24M2+lXk/Krnb0Uzy0AuenT3bFpJoK36NNYyT+ TPJYbj4mGj5niTq32Dest0XxeNg7zzJyZlIGY9WGdRI/xTGB7PkZ6kz28PPcGit023 ZyKXr9sThX8GnovXicpC8sBOcTQqXb4jVQYCrZlw= Date: Fri, 05 Sep 2025 17:27:17 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,yosryahmed@google.com,ying.huang@linux.alibaba.com,willy@infradead.org,shikemeng@huaweicloud.com,oliver.sang@intel.com,nphamcs@gmail.com,lorenzo.stoakes@oracle.com,hughd@google.com,hannes@cmpxchg.org,david@redhat.com,chrisl@kernel.org,bhe@redhat.com,baolin.wang@linux.alibaba.com,baohua@kernel.org,kasong@tencent.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-swap-wrap-swap-cache-replacement-with-a-helper.patch added to mm-new branch Message-Id: <20250906002717.C3EBAC4CEF1@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm, swap: wrap swap cache replacement with a helper has been added to the -mm mm-new branch. Its filename is mm-swap-wrap-swap-cache-replacement-with-a-helper.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-wrap-swap-cache-replacement-with-a-helper.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Kairui Song Subject: mm, swap: wrap swap cache replacement with a helper Date: Sat, 6 Sep 2025 03:13:52 +0800 There are currently three swap cache users that are trying to replace an existing folio with a new one: huge memory splitting, migration, and shmem replacement. What they are doing is quite similar. Introduce a common helper for this. In later commits, they can be easily switched to use the swap table by updating this helper. The newly added helper also makes the swap cache API better defined, and debugging is easier. Link: https://lkml.kernel.org/r/20250905191357.78298-11-ryncsn@gmail.com Signed-off-by: Kairui Song Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chris Li Cc: David Hildenbrand Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kemeng Shi Cc: kernel test robot Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Nhat Pham Cc: Yosry Ahmed Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/huge_memory.c | 5 ++--- mm/migrate.c | 11 +++-------- mm/shmem.c | 10 ++-------- mm/swap.h | 3 +++ mm/swap_state.c | 32 ++++++++++++++++++++++++++++++++ 5 files changed, 42 insertions(+), 19 deletions(-) --- a/mm/huge_memory.c~mm-swap-wrap-swap-cache-replacement-with-a-helper +++ a/mm/huge_memory.c @@ -3798,9 +3798,8 @@ static int __folio_split(struct folio *f * NOTE: shmem in swap cache is not supported yet. */ if (swap_cache) { - __xa_store(&swap_cache->i_pages, - swap_cache_index(new_folio->swap), - new_folio, 0); + __swap_cache_replace_folio(swap_cache, new_folio->swap, + folio, new_folio); continue; } --- a/mm/migrate.c~mm-swap-wrap-swap-cache-replacement-with-a-helper +++ a/mm/migrate.c @@ -566,7 +566,6 @@ static int __folio_migrate_mapping(struc struct zone *oldzone, *newzone; int dirty; long nr = folio_nr_pages(folio); - long entries, i; if (!mapping) { /* Take off deferred split queue while frozen and memcg set */ @@ -615,9 +614,6 @@ static int __folio_migrate_mapping(struc if (folio_test_swapcache(folio)) { folio_set_swapcache(newfolio); newfolio->private = folio_get_private(folio); - entries = nr; - } else { - entries = 1; } /* Move dirty while folio refs frozen and newfolio not yet exposed */ @@ -627,11 +623,10 @@ static int __folio_migrate_mapping(struc folio_set_dirty(newfolio); } - /* Swap cache still stores N entries instead of a high-order entry */ - for (i = 0; i < entries; i++) { + if (folio_test_swapcache(folio)) + __swap_cache_replace_folio(mapping, folio->swap, folio, newfolio); + else xas_store(&xas, newfolio); - xas_next(&xas); - } /* * Drop cache reference from old folio by unfreezing --- a/mm/shmem.c~mm-swap-wrap-swap-cache-replacement-with-a-helper +++ a/mm/shmem.c @@ -2086,10 +2086,8 @@ static int shmem_replace_folio(struct fo struct folio *new, *old = *foliop; swp_entry_t entry = old->swap; struct address_space *swap_mapping = swap_address_space(entry); - pgoff_t swap_index = swap_cache_index(entry); - XA_STATE(xas, &swap_mapping->i_pages, swap_index); int nr_pages = folio_nr_pages(old); - int error = 0, i; + int error = 0; /* * We have arrived here because our zones are constrained, so don't @@ -2118,12 +2116,8 @@ static int shmem_replace_folio(struct fo new->swap = entry; folio_set_swapcache(new); - /* Swap cache still stores N entries instead of a high-order entry */ xa_lock_irq(&swap_mapping->i_pages); - for (i = 0; i < nr_pages; i++) { - WARN_ON_ONCE(xas_store(&xas, new)); - xas_next(&xas); - } + __swap_cache_replace_folio(swap_mapping, entry, old, new); xa_unlock_irq(&swap_mapping->i_pages); mem_cgroup_replace_folio(old, new); --- a/mm/swap.h~mm-swap-wrap-swap-cache-replacement-with-a-helper +++ a/mm/swap.h @@ -182,6 +182,9 @@ int swap_cache_add_folio(struct folio *f void swap_cache_del_folio(struct folio *folio); void __swap_cache_del_folio(struct folio *folio, swp_entry_t entry, void *shadow); +void __swap_cache_replace_folio(struct address_space *address_space, + swp_entry_t entry, + struct folio *old, struct folio *new); void swap_cache_clear_shadow(int type, unsigned long begin, unsigned long end); --- a/mm/swap_state.c~mm-swap-wrap-swap-cache-replacement-with-a-helper +++ a/mm/swap_state.c @@ -235,6 +235,38 @@ void swap_cache_del_folio(struct folio * } /** + * __swap_cache_replace_folio - Replace a folio in the swap cache. + * @mapping: Swap mapping address space. + * @entry: The first swap entry that the new folio corresponds to. + * @old: The old folio to be replaced. + * @new: The new folio. + * + * Replace a existing folio in the swap cache with a new folio. + * + * Context: Caller must ensure both folios are locked, and lock the + * swap address_space that holds the entries to be replaced. + */ +void __swap_cache_replace_folio(struct address_space *mapping, + swp_entry_t entry, + struct folio *old, struct folio *new) +{ + unsigned long nr_pages = folio_nr_pages(new); + unsigned long offset = swap_cache_index(entry); + unsigned long end = offset + nr_pages; + XA_STATE(xas, &mapping->i_pages, offset); + + VM_WARN_ON_ONCE(entry.val != new->swap.val); + VM_WARN_ON_ONCE(!folio_test_locked(old) || !folio_test_locked(new)); + VM_WARN_ON_ONCE(!folio_test_swapcache(old) || !folio_test_swapcache(new)); + + /* Swap cache still stores N entries instead of a high-order entry */ + do { + WARN_ON_ONCE(xas_store(&xas, new) != old); + xas_next(&xas); + } while (++offset < end); +} + +/** * swap_cache_clear_shadow - Clears a set of shadows in the swap cache. * @type: Indicates the swap device. * @begin: Beginning offset of the range. _ Patches currently in -mm which might be from kasong@tencent.com are mm-swap-only-scan-one-cluster-in-fragment-list.patch mm-swap-remove-fragment-clusters-counter.patch mm-swap-prefer-nonfull-over-free-clusters.patch mm-mincore-swap-consolidate-swap-cache-checking-for-mincore.patch mm-mincore-use-a-helper-for-checking-the-swap-cache.patch mm-page-writeback-drop-usage-of-folio_index.patch mm-swap-use-unified-helper-for-swap-cache-look-up.patch mm-swap-fix-swap-cahe-index-error-when-retrying-reclaim.patch mm-swap-check-page-poison-flag-after-locking-it.patch mm-swap-always-lock-and-check-the-swap-cache-folio-before-use.patch mm-swap-rename-and-move-some-swap-cluster-definition-and-helpers.patch mm-swap-tidy-up-swap-device-and-cluster-info-helpers.patch mm-shmem-swap-remove-redundant-error-handling-for-replacing-folio.patch mm-swap-cleanup-swap-cache-api-and-add-kerneldoc.patch mm-swap-wrap-swap-cache-replacement-with-a-helper.patch mm-swap-use-the-swap-table-for-the-swap-cache-and-switch-api.patch mm-swap-mark-swap-address-space-ro-and-add-context-debug-check.patch mm-swap-remove-contention-workaround-for-swap-cache.patch mm-swap-implement-dynamic-allocation-of-swap-table.patch mm-swap-use-a-single-page-for-swap-table-when-the-size-fits.patch