From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 3179C3B0581 for ; Thu, 30 Jul 2026 19:26:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785439597; cv=none; b=Ieucz8IZvUhXXoubyEOcH7nF89bijXb+ozvMeiRwywf2SbnIn32Tc2GfH1WqkDvNFOdsKQ2OQYcoaFTUxQ33pMPuhfl1PGOVQN9kM2H3Wjc5anSb+03EMXacaU6QBbJIjmXBtCh/MJMxuLfXnYw06Zu/8CNpU+Om3riBYJ0T6NQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785439597; c=relaxed/simple; bh=yN4O2b4AWuOvFBxbY09Cv/au4l0uvd2AEZsg7by7WlE=; h=Date:To:From:Subject:Message-Id; b=axzSySjvtqreA8mMtSWh9MXxiTId3EfywPYZq7XyXMOYlsvG1TyUZN3HkX1X6DXcZrhfD9xRFpkmFmoRHP9yTxuXWA3l7ykPH4ZWTDYgAB4L2PMgbP6wm5ObVu7uOSDYSXcL7KagJCXkQv3v7xAlkULOX+X0Vsj3CoH2ViGBWg0= 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=JkxFoyJk; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="JkxFoyJk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F83D1F00A3D; Thu, 30 Jul 2026 19:26:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1785439592; bh=78Yu7NF0dxITQcPzODhRvQfzpIC/qOd2ew9b8u6yUso=; h=Date:To:From:Subject; b=JkxFoyJko90p3wp2kIG78fBq1iyK6hgA6LQr3HjnDy4pcgsI3ebI759suVWn7iA6A BT7HdgKc3DfRTNZodYWCRp7T1xEHZGzXTjT0zMxAFcAiuunSzdiVYgVeckpe+GsEMt +YeK4YKLbZZHVF465Mh/ETc43HkPAwwyTLWPwJwY= Date: Thu, 30 Jul 2026 12:26:32 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,ryan.roberts@arm.com,riel@surriel.com,osalvador@suse.de,muchun.song@linux.dev,ljs@kernel.org,liam@infradead.org,lance.yang@linux.dev,jannh@google.com,harry@kernel.org,david@kernel.org,anshuman.khandual@arm.com,dev.jain@arm.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-rmap-refactor-some-code-around-lazyfree-folio-unmapping.patch added to mm-unstable branch Message-Id: <20260730192632.9F83D1F00A3D@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/rmap: refactor some code around lazyfree folio unmapping has been added to the -mm mm-unstable branch. Its filename is mm-rmap-refactor-some-code-around-lazyfree-folio-unmapping.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rmap-refactor-some-code-around-lazyfree-folio-unmapping.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm 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 various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Dev Jain Subject: mm/rmap: refactor some code around lazyfree folio unmapping Date: Thu, 30 Jul 2026 09:45:54 +0000 For lazyfree folio unmapping, after clearing the ptes we must abort the operation if the folio got dirtied or it has unexpected references. Refactor this logic into a function which will return whether we need to abort or not. If we abort, we restore the ptes and bail out of try_to_unmap_one. Otherwise adjust the rss stats of the mm and jump to a label. Also rename that label from "discard" to "finish_unmap"; the former is appropriate in the lazyfree context, but the code following the label is executed for other successful unmap code paths too, so 'discard' does not sound correct for them. No functional change intended. Link: https://lore.kernel.org/20260730094559.418003-4-dev.jain@arm.com Signed-off-by: Dev Jain Acked-by: David Hildenbrand (Arm) Cc: Anshuman Khandual Cc: Harry Yoo Cc: Jann Horn Cc: Lance Yang Cc: Liam R. Howlett Cc: Lorenzo Stoakes (ARM) Cc: Muchun Song Cc: Oscar Salvador Cc: Rik van Riel Cc: Ryan Roberts Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/rmap.c | 87 ++++++++++++++++++++++++++++------------------------ 1 file changed, 48 insertions(+), 39 deletions(-) --- a/mm/rmap.c~mm-rmap-refactor-some-code-around-lazyfree-folio-unmapping +++ a/mm/rmap.c @@ -2068,6 +2068,50 @@ range_end: return ret; } +static bool ttu_anon_lazyfree_folio(struct vm_area_struct *vma, + struct folio *folio, unsigned long nr_pages) +{ + int ref_count, map_count; + + /* + * Synchronize with gup_pte_range(): + * - clear PTE; barrier; read refcount + * - inc refcount; barrier; read PTE + */ + smp_mb(); + + ref_count = folio_ref_count(folio); + map_count = folio_mapcount(folio); + + /* + * Order reads for page refcount and dirty flag + * (see comments in __remove_mapping()). + */ + smp_rmb(); + + if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) { + /* + * redirtied either using the page table or a previously + * obtained GUP reference. + */ + folio_set_swapbacked(folio); + return false; + } + + /* + * Additional references could be due to GUP or speculative lookups. + * GUP users must mark the folio dirty if there was a modification. + * This folio cannot be reclaimed right now either way, so act just + * like nothing happened. We'll come back here later and detect if the + * folio was dirtied when the additional reference is gone. + */ + if (ref_count != 1 + map_count) + return false; + + add_mm_counter(vma->vm_mm, MM_ANONPAGES, -nr_pages); + return true; +} + /* * @arg: enum ttu_flags will be passed to this argument */ @@ -2261,47 +2305,12 @@ static bool try_to_unmap_one(struct foli /* MADV_FREE page check */ if (!folio_test_swapbacked(folio)) { - int ref_count, map_count; - - /* - * Synchronize with gup_pte_range(): - * - clear PTE; barrier; read refcount - * - inc refcount; barrier; read PTE - */ - smp_mb(); - - ref_count = folio_ref_count(folio); - map_count = folio_mapcount(folio); - - /* - * Order reads for page refcount and dirty flag - * (see comments in __remove_mapping()). - */ - smp_rmb(); - - if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) { - /* - * redirtied either using the page table or a previously - * obtained GUP reference. - */ - set_ptes(mm, address, pvmw.pte, pteval, nr_pages); - folio_set_swapbacked(folio); - goto walk_abort; - } else if (ref_count != 1 + map_count) { - /* - * Additional reference. Could be a GUP reference or any - * speculative reference. GUP users must mark the folio - * dirty if there was a modification. This folio cannot be - * reclaimed right now either way, so act just like nothing - * happened. - * We'll come back here later and detect if the folio was - * dirtied when the additional reference is gone. - */ + if (!ttu_anon_lazyfree_folio(vma, folio, + nr_pages)) { set_ptes(mm, address, pvmw.pte, pteval, nr_pages); goto walk_abort; } - add_mm_counter(mm, MM_ANONPAGES, -nr_pages); - goto discard; + goto finish_unmap; } if (folio_dup_swap(folio, subpage) < 0) { @@ -2359,7 +2368,7 @@ static bool try_to_unmap_one(struct foli */ add_mm_counter(mm, mm_counter_file(folio), -nr_pages); } -discard: +finish_unmap: folio_remove_rmap_ptes(folio, subpage, nr_pages, vma); if (vma->vm_flags & VM_LOCKED) mlock_drain_local(); _ Patches currently in -mm which might be from dev.jain@arm.com are mm-rmap-use-huge_ptep_get-in-try_to_unmap_one.patch mm-rmap-use-huge_ptep_get-in-try_to_migrate_one.patch mm-migrate-use-huge_ptep_get-in-remove_migration_pte.patch mm-page_vma_mapped-use-huge_ptep_get-for-hugetlb.patch mm-mprotect-use-huge_ptep_get-for-hugetlb.patch mm-rmap-convert-page-folio-for-hwpoison-checks.patch mm-rmap-add-try_to_unmap_poisoned_hugetlb_one.patch mm-rmap-refactor-some-code-around-lazyfree-folio-unmapping.patch mm-rmap-refactor-anon-folio-unmap-in-try_to_unmap_one.patch mm-rmap-add-anon-folio-unmap-dispatcher.patch mm-memory-move-pte_install_uffd_wp_if_needed-into-memoryc.patch mm-memory-batch-set-uffd-wp-markers-during-zapping.patch mm-rmap-batch-unmap-file-folios-belonging-to-uffd-wp-vmas.patch