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 2CEFC3B0AD2 for ; Thu, 19 Mar 2026 10:39:39 +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=1773916779; cv=none; b=pml9tdCgWB1uLf+jbsJbT2FInIem2jP69uIoEk423feoDf/rYwxsxiuNUnMUd9Kf4EgtEg6S52E7feBSfBhfMcbikqcKhi9MZD0SKg49ZGLYdzQpw8roe45J19TzXK+55gKRHYRvqECyUEtkuAkjShwoJJ6rSrFXdU2Mz54wzr4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773916779; c=relaxed/simple; bh=Wg7+9Y2K5YQyAEuOcnbcZyxttxGObbw3kzU8lDtgx34=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kUfBmaShXegqVQUqPUzL2DPDrSIbk0iY32NmCp3xCDISwrgC8WSqSLCre+EKxpGo0Q4o5qkmnzd85lP06Kqm+JVs93iqBiasDvVqu75MF7WlMcWDstlWK2cQJwEHXf5Ej7OW0UrfkIZT+RYItK4boiPtojpb4XmvSHUJv+d4zjw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=q6HaUy1m; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="q6HaUy1m" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D49FC19424; Thu, 19 Mar 2026 10:39:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773916778; bh=Wg7+9Y2K5YQyAEuOcnbcZyxttxGObbw3kzU8lDtgx34=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=q6HaUy1ml9AOF9G/OXp7Hs7j58PoXZGVhBiZYEyXbwf61DbMxN6wwejhcIgfQwr+n dRZkEXCL0Lae9PFzGWP85V8N+2JtJUTjf0k/Jgot4KlwfDmsW7CFVhMYFj2CIWn6oa DTQYu1KnEGvsM505J1IUomTzs+8KCb4QbT8vdinTva5+lIsnYO3aQqmjZlkqH7j1y7 aPzsjXqfZnXFsNReiGIRgnkT1cYv+MwCEHp7/n3THJovmltsL8LHlC99eZx8EwL0vW 1LId9T6gJSmvjyewIuiPUJiUlMY32PNdZ2/j8hDxxY23tcrODHGqGM/vz+vq7kgVHI DNeoWq5j4TxPQ== Date: Thu, 19 Mar 2026 10:39:36 +0000 From: "Lorenzo Stoakes (Oracle)" To: Qi Zheng Cc: David Hildenbrand , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH 1/8] mm/huge_memory: simplify vma_is_specal_huge() Message-ID: References: <84712e37721c557f887e4a405759be31a4961100.1773865827.git.ljs@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Mar 19, 2026 at 11:16:20AM +0800, Qi Zheng wrote: > > > On 3/19/26 4:39 AM, Lorenzo Stoakes (Oracle) wrote: > > This function is confused - it overloads the term 'special' yet again, > > checks for DAX but in many cases the code explicitly excludes DAX before > > invoking the predicate. > > > > It also unnecessarily checks for vma->vm_file - this has to be present for > > a driver to have set VMA_MIXEDMAP_BIT or VMA_PFNMAP_BIT. > > > > In fact, a far simpler form of this is to reverse the DAX predicate and > > return false if DAX is set. > > > > This makes sense from the point of view of 'special' as in > > vm_normal_page(), as DAX actually does potentially have retrievable folios. > > > > Also there's no need to have this in mm.h so move it to huge_memory.c. > > > > Signed-off-by: Lorenzo Stoakes (Oracle) > > --- > > include/linux/huge_mm.h | 4 ++-- > > include/linux/mm.h | 16 ---------------- > > mm/huge_memory.c | 30 +++++++++++++++++++++++------- > > 3 files changed, 25 insertions(+), 25 deletions(-) > > > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > > index bd7f0e1d8094..61fda1672b29 100644 > > --- a/include/linux/huge_mm.h > > +++ b/include/linux/huge_mm.h > > @@ -83,7 +83,7 @@ extern struct kobj_attribute thpsize_shmem_enabled_attr; > > * file is never split and the MAX_PAGECACHE_ORDER limit does not apply to > > * it. Same to PFNMAPs where there's neither page* nor pagecache. > > */ > > -#define THP_ORDERS_ALL_SPECIAL \ > > +#define THP_ORDERS_ALL_SPECIAL_DAX \ > > As mentioned in the comments, the pfnmap case is also include in the > 'special' case, right? Yeah special = pfnmap, mixedmap. so renaming to SPECIAL_DAX to make clear it's either dax or 'special' in the meaning of vm_normal_page(). > > > (BIT(PMD_ORDER) | BIT(PUD_ORDER)) > > #define THP_ORDERS_ALL_FILE_DEFAULT \ > > ((BIT(MAX_PAGECACHE_ORDER + 1) - 1) & ~BIT(0)) > > @@ -92,7 +92,7 @@ extern struct kobj_attribute thpsize_shmem_enabled_attr; > > * Mask of all large folio orders supported for THP. > > */ > > #define THP_ORDERS_ALL \ > > - (THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_SPECIAL | THP_ORDERS_ALL_FILE_DEFAULT) > > + (THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_SPECIAL_DAX | THP_ORDERS_ALL_FILE_DEFAULT) > > enum tva_type { > > TVA_SMAPS, /* Exposing "THPeligible:" in smaps. */ > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 6f0a3edb24e1..50d68b092204 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -5077,22 +5077,6 @@ long copy_folio_from_user(struct folio *dst_folio, > > const void __user *usr_src, > > bool allow_pagefault); > > -/** > > - * vma_is_special_huge - Are transhuge page-table entries considered special? > > - * @vma: Pointer to the struct vm_area_struct to consider > > - * > > - * Whether transhuge page-table entries are considered "special" following > > - * the definition in vm_normal_page(). > > - * > > - * Return: true if transhuge page-table entries should be considered special, > > - * false otherwise. > > - */ > > -static inline bool vma_is_special_huge(const struct vm_area_struct *vma) > > -{ > > - return vma_is_dax(vma) || (vma->vm_file && > > - (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))); > > -} > > - > > #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */ > > #if MAX_NUMNODES > 1 > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 3fc02913b63e..f76edfa91e96 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -100,6 +100,14 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) > > return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); > > } > > +/* If returns true, we are unable to access the VMA's folios. */ > > +static bool vma_is_special_huge(struct vm_area_struct *vma) > > +{ > > + if (vma_is_dax(vma)) > > + return false; > > + return vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT); > > +} > > + > > unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, > > vm_flags_t vm_flags, > > enum tva_type type, > > @@ -113,8 +121,8 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, > > /* Check the intersection of requested and supported orders. */ > > if (vma_is_anonymous(vma)) > > supported_orders = THP_ORDERS_ALL_ANON; > > - else if (vma_is_special_huge(vma)) > > - supported_orders = THP_ORDERS_ALL_SPECIAL; > > + else if (vma_is_dax(vma) || vma_is_special_huge(vma)) > > + supported_orders = THP_ORDERS_ALL_SPECIAL_DAX; > > else > > supported_orders = THP_ORDERS_ALL_FILE_DEFAULT; > > @@ -2431,7 +2439,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > > tlb->fullmm); > > arch_check_zapped_pmd(vma, orig_pmd); > > tlb_remove_pmd_tlb_entry(tlb, pmd, addr); > > - if (!vma_is_dax(vma) && vma_is_special_huge(vma)) { > > + if (vma_is_special_huge(vma)) { > > if (arch_needs_pgtable_deposit()) > > zap_deposited_table(tlb->mm, pmd); > > spin_unlock(ptl); > > @@ -2933,7 +2941,7 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, > > orig_pud = pudp_huge_get_and_clear_full(vma, addr, pud, tlb->fullmm); > > arch_check_zapped_pud(vma, orig_pud); > > tlb_remove_pud_tlb_entry(tlb, pud, addr); > > - if (!vma_is_dax(vma) && vma_is_special_huge(vma)) { > > + if (vma_is_special_huge(vma)) { > > spin_unlock(ptl); > > /* No zero page support yet */ > > } else { > > @@ -3084,7 +3092,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > > */ > > if (arch_needs_pgtable_deposit()) > > zap_deposited_table(mm, pmd); > > - if (!vma_is_dax(vma) && vma_is_special_huge(vma)) > > + if (vma_is_special_huge(vma)) > > return; > > if (unlikely(pmd_is_migration_entry(old_pmd))) { > > const softleaf_t old_entry = softleaf_from_pmd(old_pmd); > > @@ -4645,8 +4653,16 @@ static void split_huge_pages_all(void) > > static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma) > > { > > - return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) || > > - is_vm_hugetlb_page(vma); > > + if (vma_is_dax(vma)) > > + return true; > > + if (vma_is_special_huge(vma)) > > + return true; > > + if (vma_test(vma, VMA_IO_BIT)) > > + return true; > > + if (is_vm_hugetlb_page(vma)) > > + return true; > > + > > + return false; > > } > > static int split_huge_pages_pid(int pid, unsigned long vaddr_start, >