diff mbox series

[1/8] mm: Introduce vma_is_special_huge

Message ID 20191203132239.5910-2-thomas_os@shipmail.org (mailing list archive)
State New, archived
Headers show
Series Huge page-table entries for TTM | expand

Commit Message

Thomas Hellström (Intel) Dec. 3, 2019, 1:22 p.m. UTC 
From: Thomas Hellstrom <thellstrom@vmware.com>

For VM_PFNMAP and VM_MIXEDMAP vmas that want to support transhuge pages
and -page table entries, introduce vma_is_special_huge() that takes the
same codepaths as vma_is_dax().

The use of "special" follows the definition in memory.c, vm_normal_page():
"Special" mappings do not wish to be associated with a "struct page"
(either it doesn't exist, or it exists but they don't want to touch it)

For PAGE_SIZE pages, "special" is determined per page table entry to be
able to deal with COW pages. But since we don't have huge COW pages,
we can classify a vma as either "special huge" or "normal huge".

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
---
 include/linux/mm.h | 6 ++++++
 mm/huge_memory.c   | 6 +++---
 2 files changed, 9 insertions(+), 3 deletions(-)

Comments

Andrew Morton March 1, 2020, 4:04 a.m. UTC | #1 
On Tue,  3 Dec 2019 14:22:32 +0100 Thomas Hellström (VMware) <thomas_os@shipmail.org> wrote:

> From: Thomas Hellstrom <thellstrom@vmware.com>
> 
> For VM_PFNMAP and VM_MIXEDMAP vmas that want to support transhuge pages
> and -page table entries, introduce vma_is_special_huge() that takes the
> same codepaths as vma_is_dax().
> 
> The use of "special" follows the definition in memory.c, vm_normal_page():
> "Special" mappings do not wish to be associated with a "struct page"
> (either it doesn't exist, or it exists but they don't want to touch it)
> 
> For PAGE_SIZE pages, "special" is determined per page table entry to be
> able to deal with COW pages. But since we don't have huge COW pages,
> we can classify a vma as either "special huge" or "normal huge".
> 
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2822,6 +2822,12 @@ extern long copy_huge_page_from_user(struct page *dst_page,
>  				const void __user *usr_src,
>  				unsigned int pages_per_huge_page,
>  				bool allow_pagefault);
> +static inline bool vma_is_special_huge(struct vm_area_struct *vma)
> +{
> +	return vma_is_dax(vma) || (vma->vm_file &&
> +				   (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)));
> +}

Some documetnation would be nice.  Not only what it does, but why it
does it.  ie, what is the *meaning* of vma_is_spacial_huge(vma)==true?
diff mbox series

Patch

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0133542d69c9..886a1f899887 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2822,6 +2822,12 @@  extern long copy_huge_page_from_user(struct page *dst_page,
 				const void __user *usr_src,
 				unsigned int pages_per_huge_page,
 				bool allow_pagefault);
+static inline bool vma_is_special_huge(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 */
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 41a0fbddc96b..f8d24fc3f4df 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1789,7 +1789,7 @@  int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
 			tlb->fullmm);
 	tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
-	if (vma_is_dax(vma)) {
+	if (vma_is_special_huge(vma)) {
 		if (arch_needs_pgtable_deposit())
 			zap_deposited_table(tlb->mm, pmd);
 		spin_unlock(ptl);
@@ -2053,7 +2053,7 @@  int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	 */
 	pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
 	tlb_remove_pud_tlb_entry(tlb, pud, addr);
-	if (vma_is_dax(vma)) {
+	if (vma_is_special_huge(vma)) {
 		spin_unlock(ptl);
 		/* No zero page support yet */
 	} else {
@@ -2162,7 +2162,7 @@  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))
+		if (vma_is_special_huge(vma))
 			return;
 		page = pmd_page(_pmd);
 		if (!PageDirty(page) && pmd_dirty(_pmd))