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 5AE415478D; Sat, 5 Sep 2026 18:48:08 +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=1788634090; cv=none; b=b/uZx/odGsRu+3M0bZ1l3yIzsr7klsbLnfwtQTN5RY8FTgIZ09z8pdRfUBeV1imNhVztnt4nZ1YH7CwtlcJxBBy0wuLGoyFMxO2xGCNWBT3r5iS0qw4ByCm9fI5uancQN/juqcG2QQ/4JQEzmu2rzB8G48nCRrs3Jht0CzUUnyc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788634090; c=relaxed/simple; bh=udFvITsnvIhSY/MPk2MhZDn535w+91kb/b9JCEEtU78=; h=Date:To:From:Subject:Message-Id; b=IPSZVso4ekYWqAJVEkXxvTvjAWihhUdQOQeqbt93/0LztsGxzfLgC/yGsoTeKa0hIdjp0w5drOUMx3OI4sNHS9NfTsy/N/NQtnEG61cKidvHC463VmXsFrNuka1csMeGsc66VEgo6PMbwjsSMFHTFnVohldI/U/+rWbP+tRrf0E= 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=Ju1+/rr+; 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="Ju1+/rr+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B94B81F00A3A; Sat, 5 Sep 2026 18:48:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788634088; bh=ycEAbdjQ92e8uYTru9iK552ET8xDhXY5zPrQqkum/3c=; h=Date:To:From:Subject; b=Ju1+/rr+Fori2x8rVpQmS8hOsDJfwEenP9CbgIZ9iisk0gdir8GL0DOQ2Co1V8RHG c2RxzQ0d+b9XTtOZlq7bNwHH2L5hSMHPAJNhQhmlaEZcwuE9X0odnjVv7kqoCU72L6 C4EqAmT8MEOOu6YLNQwTeRr8ANZeJ/AYseV56J/A= Date: Sat, 05 Sep 2026 11:48:08 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,stable@vger.kernel.org,sj@kernel.org,saravanand@crusoe.ai,ryan.roberts@arm.com,peterx@redhat.com,liam@infradead.org,lance.yang@linux.dev,jgg@ziepe.ca,dev.jain@arm.com,david@kernel.org,clg@redhat.com,baolin.wang@linux.alibaba.com,baohua@kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] mm-huge_memory-bypass-thp-tuneables-for-huge-pfnmap-mappings.patch removed from -mm tree Message-Id: <20260905184808.B94B81F00A3A@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/huge_memory: bypass THP tuneables for huge pfnmap mappings has been removed from the -mm tree. Its filename was mm-huge_memory-bypass-thp-tuneables-for-huge-pfnmap-mappings.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: "Lorenzo Stoakes (ARM)" Subject: mm/huge_memory: bypass THP tuneables for huge pfnmap mappings Date: Thu, 27 Aug 2026 20:55:57 +0100 The sysfs THP tuneables at /sys/kernel/mm/transparent_huge_pages/ rather confusingly only control the behaviour of THP in some instances. They are not applicable to MADV_COLLAPSE operations, nor to DAX mappings. Long-term, THP is predicated upon compaction being able to obtain large folios to populate THP ranges. However, vm_normal_folio() returns NULL for PFN map mappings, thus their reference count is maintained by the driver, not core mm. As a consequence, the folios are not subject to reclaim nor compaction, so are not truly part of the THP mechanism at all. However, since commit 5dd40721f147 ("mm: allow THP orders for PFNMAPs") introduced the ability to establish huge PFN maps, they have been subject to THP tuneables. This is incorrect - if a huge PFN map is available (defined by vma->vm_ops->huge_fault being non-NULL for a VMA_PFNMAP_BIT VMA), then it should be mapped huge upon fault-in. Correct this by explicitly checking for this while ensuring that smaps continues to accurately report THPeligible statistics. While here, abstract the entire file-backed THP check in vma_can_map_huge_file(), with sensible separation of logic into helper functions. Note that drm_gem_shmem_mmap() and panthor_gem_mmap() establish huge PFN maps of shmem folios, however they are marked unevictable in drm_gem_get_pages(), and in any case would fail the reference check in __remove_mapping() even if they weren't. Failing to map huge PFN maps has resulted in significant real-world performance degradation, see links for details. [ziy@nvidia.com: rename some functions] Link: https://lore.kernel.org/DL1HIHWYJ7TB.1CY76SJS0V03L@nvidia.com Link: https://lore.kernel.org/20260827-hugepfn-allowable-orders-v1-1-94819c8807c8@kernel.org Fixes: 5dd40721f147 ("mm: allow THP orders for PFNMAPs") Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Zi Yan Reported-by: Cedric Le Goater Closes: https://lore.kernel.org/linux-mm/20260805055544.1568534-1-clg@redhat.com/ Reported-by: Saravanan D Closes: https://lore.kernel.org/linux-mm/20260821070520.25759-1-saravanand@crusoe.ai/ Reviewed-by: Zi Yan Tested-by: Saravanan D Tested-by: Lance Yang Reviewed-by: SJ Park Reviewed-by: Baolin Wang Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Jason Gunthorpe Cc: Liam R. Howlett Cc: Peter Xu Cc: Ryan Roberts Cc: Signed-off-by: Andrew Morton --- mm/huge_memory.c | 86 +++++++++++++++++++++++++++++++++------------ 1 file changed, 64 insertions(+), 22 deletions(-) --- a/mm/huge_memory.c~mm-huge_memory-bypass-thp-tuneables-for-huge-pfnmap-mappings +++ a/mm/huge_memory.c @@ -92,7 +92,7 @@ unsigned long huge_anon_orders_madvise _ unsigned long huge_anon_orders_inherit __read_mostly; static bool anon_orders_configured __initdata; -static inline bool file_thp_enabled(struct vm_area_struct *vma) +static inline bool file_thp_enabled(const struct vm_area_struct *vma) { struct inode *inode; @@ -118,6 +118,67 @@ static bool vma_is_special_huge(const st return vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT); } +static bool vma_file_bypass_thp_tuneables(const struct vm_area_struct *vma, + enum tva_type type) +{ + const bool has_huge_fault = vma->vm_ops->huge_fault; + + /* MADV_COLLAPSE ignores tuneables. */ + if (type == TVA_FORCED_COLLAPSE) + return true; + /* Huge PFN mappings are uncompactable so the policy doesn't apply. */ + if (vma_test(vma, VMA_PFNMAP_BIT) && has_huge_fault) + return true; + return false; +} + +static bool vma_file_allow_thp_tuneables(vm_flags_t vm_flags) +{ + /* THP=always? */ + if (hugepage_global_always()) + return true; + /* THP=madvise and marked MADV_HUGEPAGE? */ + if (hugepage_global_enabled() && (vm_flags & VM_HUGEPAGE)) + return true; + return false; +} + +static bool vma_file_check_thp_tuneables(const struct vm_area_struct *vma, + vm_flags_t vm_flags, enum tva_type type) +{ + return vma_file_bypass_thp_tuneables(vma, type) || + vma_file_allow_thp_tuneables(vm_flags); +} + +static bool vma_can_map_huge_file(const struct vm_area_struct *vma, + vm_flags_t vm_flags, enum tva_type type) +{ + const bool has_huge_fault = vma->vm_ops->huge_fault; + + /* + * Enforce THP collapse requirements as necessary. Anonymous vmas + * were already handled in thp_vma_allowable_orders(). + */ + if (!vma_file_check_thp_tuneables(vma, vm_flags, type)) + return false; + + switch (type) { + case TVA_PAGEFAULT: + /* + * Trust that ->huge_fault() handlers know what they are doing + * in fault path. + */ + return has_huge_fault; + case TVA_SMAPS: + if (has_huge_fault) + return true; + fallthrough; + default: + /* Only regular file is valid in collapse path. */ + return file_thp_enabled(vma); + } +} + unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, vm_flags_t vm_flags, enum tva_type type, @@ -190,27 +251,8 @@ unsigned long __thp_vma_allowable_orders vma, vma_start_pgoff(vma), 0, forced_collapse); - if (!vma_is_anonymous(vma)) { - /* - * Enforce THP collapse requirements as necessary. Anonymous vmas - * were already handled in thp_vma_allowable_orders(). - */ - if (!forced_collapse && - (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) && - !hugepage_global_always()))) - return 0; - - /* - * Trust that ->huge_fault() handlers know what they are doing - * in fault path. - */ - if (((in_pf || smaps)) && vma->vm_ops->huge_fault) - return orders; - /* Only regular file is valid in collapse path */ - if (((!in_pf || smaps)) && file_thp_enabled(vma)) - return orders; - return 0; - } + if (!vma_is_anonymous(vma)) + return vma_can_map_huge_file(vma, vm_flags, type) ? orders : 0; if (vma_is_temporary_stack(vma)) return 0; _ Patches currently in -mm which might be from ljs@kernel.org are mm-vma-correctly-unaccount-on-mmap_prepare-failure.patch mm-vmpressure-remove-window-size-todo.patch tools-testing-selftests-mm-add-missing-gitignore-entries.patch mm-move-drivers-char-memc-to-mm-char-memc.patch mm-implement-file_is_dev_zero-to-uniquely-identify-dev-zero.patch mm-vma-only-permit-map_private-dev-zero-to-be-mapped-anonymous.patch mm-vma-make-map_private-mapped-dev-zero-mappings-truly-anonymous.patch tools-testing-vma-add-test-to-assert-map_private-dev-zero-is-anon.patch tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch