From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 B535F9460 for ; Thu, 19 Mar 2026 03:16:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773890197; cv=none; b=sv2aUFoIUkX5CJxkk4xWXZyESgal/e5z9VYKudPNhbV+Pz1bsyazYdFqMV4E8MsvgHy5VQjp2UAivA0Rhdr+mCCSoTwvDGgLyXnJvXsQr6guii+nHE/TEY7zzACjgWe97b5TegNIBxMjCsY18mQxyfU9CJQBb/OuS9DH6y1i7bw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773890197; c=relaxed/simple; bh=ZwiE8HdU1ROSrhURp7OUmpMu4cLhJe7W/iJU8D2+e4o=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SU1lsc1s4YdlhPxH3p/DLXe/3m3urMmLfkMAxKWNmfedjDBeXus7GgZcHbemEJMf1bivHJKBPZHdckD9eAQtFKm3W3yBM2PKdlmwCu9zDDtwBSmVBHro3EDwF0nCCSmf/gVpXoj2nL8WIoW917mgKEIbOymZ3v0eu5O+PfzTWZg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=iK+YWR9w; arc=none smtp.client-ip=91.218.175.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="iK+YWR9w" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773890193; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=u9mrbCOmG4x77bnH5kDlZrIOueqBy+MG8B+nctQHjJw=; b=iK+YWR9wTlQKAnQBbZuoNU4JCZgqBq5Xg3Oe8ViaOu8FDMK6xsbhz85mUkz5Q+RlMiPS0J 9Gq7nw6gk4lPuDBLudROgvk4ec9G9leSYkWICSN64uoFtWd/MwsnIy7t55vDCxG3xMQrk8 eG4eANEbPI9U0vYA36TyX6V47PzLfRI= Date: Thu, 19 Mar 2026 11:16:20 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH 1/8] mm/huge_memory: simplify vma_is_specal_huge() To: "Lorenzo Stoakes (Oracle)" 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 References: <84712e37721c557f887e4a405759be31a4961100.1773865827.git.ljs@kernel.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <84712e37721c557f887e4a405759be31a4961100.1773865827.git.ljs@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT 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? > (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,