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FAILED: patch "[PATCH] mm/hmm.c: allow VM_MIXEDMAP to work with hmm_range_fault" failed to apply to 4.19-stable tree

PATCH [email protected] 1 participant 1 message Jan 24, 2022

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The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 87c01d57fa23de82fff593a7d070933d08755801 Mon Sep 17 00:00:00 2001
From: Alistair Popple <[email protected]>
Date: Fri, 14 Jan 2022 14:09:31 -0800
Subject: [PATCH] mm/hmm.c: allow VM_MIXEDMAP to work with hmm_range_fault

hmm_range_fault() can be used instead of get_user_pages() for devices which allow faulting however unlike get_user_pages() it will return an error when used on a VM_MIXEDMAP range.

To make hmm_range_fault() more closely match get_user_pages() remove this restriction. This requires dealing with the !ARCH_HAS_PTE_SPECIAL case in hmm_vma_handle_pte(). Rather than replicating the logic of vm_normal_page() call it directly and do a check for the zero pfn similar to what get_user_pages() currently does.

Also add a test to hmm selftest to verify functionality.

Link https://lkml.kernel.org/r/[email protected] open here
Fixes da4c3c735ea4 ("mm/hmm/mirror: helper to snapshot CPU page table")
Signed-off-by Alistair Popple <[email protected]>
Reviewed-by Jason Gunthorpe <[email protected]>
Cc Jerome Glisse <[email protected]>
Cc John Hubbard <[email protected]>
Cc Zi Yan <[email protected]>
Cc Ralph Campbell <[email protected]>
Cc Felix Kuehling <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
lib/test_hmm.c +24 -0
index e2ce8f9b7605..767538089a62 100644
@@ -1086,9 +1086,33 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp,
 	return 0;
 }
 
+static int dmirror_fops_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	unsigned long addr;
+
+	for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) {
+		struct page *page;
+		int ret;
+
+		page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		if (!page)
+			return -ENOMEM;
+
+		ret = vm_insert_page(vma, addr, page);
+		if (ret) {
+			__free_page(page);
+			return ret;
+		}
+		put_page(page);
+	}
+
+	return 0;
+}
+
 static const struct file_operations dmirror_fops = {
 	.open		= dmirror_fops_open,
 	.release	= dmirror_fops_release,
+	.mmap		= dmirror_fops_mmap,
 	.unlocked_ioctl = dmirror_fops_unlocked_ioctl,
 	.llseek		= default_llseek,
 	.owner		= THIS_MODULE,
mm/hmm.c +3 -2
index 842e26599238..bd56641c79d4 100644
@@ -300,7 +300,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 	 * Since each architecture defines a struct page for the zero page, just
 	 * fall through and treat it like a normal page.
 	 */
-	if (pte_special(pte) && !pte_devmap(pte) &&
+	if (!vm_normal_page(walk->vma, addr, pte) &&
+	    !pte_devmap(pte) &&
 	    !is_zero_pfn(pte_pfn(pte))) {
 		if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
 			pte_unmap(ptep);

@@ -518,7 +519,7 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
 	struct hmm_range *range = hmm_vma_walk->range;
 	struct vm_area_struct *vma = walk->vma;
 
-	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) &&
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) &&
 	    vma->vm_flags & VM_READ)
 		return 0;
tools/testing/selftests/vm/hmm-tests.c +42 -0

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