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From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org
Cc: pv-drivers@vmware.com, linux-graphics-maintainer@vmware.com,
	"Thomas Hellstrom" <thellstrom@vmware.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Michal Hocko" <mhocko@suse.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"Ralph Campbell" <rcampbell@nvidia.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Christian König" <christian.koenig@amd.com>
Subject: [PATCH 2/8] mm: Split huge pages on write-notify or COW
Date: Tue,  3 Dec 2019 14:22:33 +0100
Message-ID: <20191203132239.5910-3-thomas_os@shipmail.org> (raw)
In-Reply-To: <20191203132239.5910-1-thomas_os@shipmail.org>

From: Thomas Hellstrom <thellstrom@vmware.com>

We currently only do COW and write-notify on the PTE level, so if the
huge_fault() handler returns VM_FAULT_FALLBACK on wp faults,
split the huge pages and page-table entries. Also do this for huge PUDs
if there is no huge_fault() handler and the vma is not anonymous, similar
to how it's done for PMDs.

Note that fs/dax.c does the splitting in the huge_fault() handler, but as
huge_fault() is implemented by modules we need to consider whether to
export the splitting functions for use in the modules or whether to try
to keep calls in the core. Opt for the latter. A follow-up patch can
remove the dax.c split_huge_pmd() if needed.

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>
---
 mm/memory.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 78517a5bb8ac..7ede2456a76f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3851,11 +3851,14 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
 {
 	if (vma_is_anonymous(vmf->vma))
 		return do_huge_pmd_wp_page(vmf, orig_pmd);
-	if (vmf->vma->vm_ops->huge_fault)
-		return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
+	if (vmf->vma->vm_ops->huge_fault) {
+		vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
 
-	/* COW handled on pte level: split pmd */
-	VM_BUG_ON_VMA(vmf->vma->vm_flags & VM_SHARED, vmf->vma);
+		if (!(ret & VM_FAULT_FALLBACK))
+			return ret;
+	}
+
+	/* COW or write-notify handled on pte level: split pmd. */
 	__split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL);
 
 	return VM_FAULT_FALLBACK;
@@ -3883,9 +3886,16 @@ static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	/* No support for anonymous transparent PUD pages yet */
 	if (vma_is_anonymous(vmf->vma))
-		return VM_FAULT_FALLBACK;
-	if (vmf->vma->vm_ops->huge_fault)
-		return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
+		goto split;
+	if (vmf->vma->vm_ops->huge_fault) {
+		vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
+
+		if (!(ret & VM_FAULT_FALLBACK))
+			return ret;
+	}
+split:
+	/* COW or write-notify not handled on PUD level: split pud.*/
+	__split_huge_pud(vmf->vma, vmf->pud, vmf->address);
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 	return VM_FAULT_FALLBACK;
 }
-- 
2.21.0



  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-03 13:22 [PATCH 0/8] Huge page-table entries for TTM Thomas Hellström (VMware)
2019-12-03 13:22 ` [PATCH 1/8] mm: Introduce vma_is_special_huge Thomas Hellström (VMware)
2019-12-03 13:22 ` Thomas Hellström (VMware) [this message]
2019-12-03 13:22 ` [PATCH 3/8] mm: Add vmf_insert_pfn_xxx_prot() for huge page-table entries Thomas Hellström (VMware)
2019-12-03 13:22 ` [PATCH 4/8] drm/ttm, drm/vmwgfx: Support huge TTM pagefaults Thomas Hellström (VMware)
2019-12-03 13:22 ` [PATCH 5/8] drm/vmwgfx: Support huge page faults Thomas Hellström (VMware)
2019-12-03 13:22 ` [PATCH 6/8] drm: Add a drm_get_unmapped_area() helper Thomas Hellström (VMware)
2019-12-04 11:11   ` Christian König
2019-12-04 11:36     ` Thomas Hellström (VMware)
2019-12-04 12:08       ` Christian König
2019-12-04 12:32         ` Thomas Hellström (VMware)
2019-12-04 14:40           ` Christian König
2019-12-04 15:36             ` Thomas Hellström (VMware)
2019-12-03 13:22 ` [PATCH 7/8] drm/ttm: Introduce a huge page aligning TTM range manager Thomas Hellström (VMware)
2019-12-04 11:13   ` Christian König
2019-12-04 11:45     ` Thomas Hellström (VMware)
2019-12-04 12:16       ` Christian König
2019-12-04 13:18         ` Thomas Hellström (VMware)
2019-12-04 14:02           ` Christian König
2019-12-03 13:22 ` [PATCH 8/8] drm/vmwgfx: Hook up the helpers to align buffer objects Thomas Hellström (VMware)

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