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 C430C5304A7; Wed, 23 Sep 2026 14:54:10 +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=1790175252; cv=none; b=r6DLJEsD8AlieLYJ1mbofhyw8K/vOZjndCTIrpZVUHOIUot/rxW9ENZHVTP3DeanM0R2MksIvvSG+4SJVSONIytGqK+DPpU4cTII1HQLsngyaXyLYKqmTTqUJkY1eyhtfDTOoayR9P9ul27pvY9g1ExbT+a1Fap47MaDKbXkXFk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790175252; c=relaxed/simple; bh=EG9LLvdWsV9D1RVVWKWNiFn2j0qDmxGZNIg9bRJ/eqg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pSSbtSm9AnjpbkgoM1oRXqKeU5Kw+bouZ43POnjfNPbNuGuBx446U49NId8dfmj4KmKV+tZb9t1GjUMLVT5GS7Kps7Ub7/2W0BmvSMGl1l2s2AzyBQMGEUJVvleThsR0+62Po760EdW42LvrfXZ1DMZETAqFeVfQy+SCWS9e9LI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FWUZuGUe; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FWUZuGUe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03DCA1F000FF; Wed, 23 Sep 2026 14:54:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790175250; bh=u7S0/na2UcQC1za9COpsLjPEGpLb3Dp0N22VhulecKU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FWUZuGUecCsvwVZtFZ7LhMrILQEeedFjKwo5rcPo4zhH5RUXz0xJ0MBk08bTzqly1 hzdMF9X+s2rOqLuC3VZ8/ya0yjzTzSfhzy3C07XNvxPgd4ILTeH4WHM+M6/g3+4v+9 lBpdQYzmpFmffnmH8l/R23buj9SOhpFxShMGr8dw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Lorenzo Stoakes (ARM)" , Zi Yan , Cedric Le Goater , Saravanan D , Lance Yang , SJ Park , Baolin Wang , Barry Song , David Hildenbrand , Dev Jain , Jason Gunthorpe , "Liam R. Howlett" , Peter Xu , Ryan Roberts , Andrew Morton , Sasha Levin Subject: [PATCH 6.18 369/398] mm/huge_memory: bypass THP tuneables for huge pfnmap mappings Date: Wed, 23 Sep 2026 16:07:23 +0200 Message-ID: <20260923140653.009779123@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923140643.441954610@linuxfoundation.org> References: <20260923140643.441954610@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Lorenzo Stoakes (ARM)" [ Upstream commit e384abeb559d10d6505aec053ede9368d81d4c71 ] 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 [ replaced vma_test(vma, VMA_PFNMAP_BIT) with (vma->vm_flags & VM_PFNMAP) ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- mm/huge_memory.c | 86 ++++++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 64 insertions(+), 22 deletions(-) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -84,7 +84,7 @@ 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; @@ -102,6 +102,67 @@ static inline bool file_thp_enabled(stru return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } +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->vm_flags & VM_PFNMAP) && 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, @@ -174,27 +235,8 @@ unsigned long __thp_vma_allowable_orders vma, vma->vm_pgoff, 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;