From 5ae86c8436b83762bc6cf46bea1da6ace2d3f50e Mon Sep 17 00:00:00 2001
From: Paul Gofman <pgofman@codeweavers.com>
Date: Wed, 6 May 2020 14:37:44 +0300
Subject: [PATCH 1/2] mm: Support soft dirty flag reset for VA range.

---
 fs/proc/task_mmu.c | 129 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 103 insertions(+), 26 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3cec6fbef725..7c7865028f10 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1032,6 +1032,8 @@ enum clear_refs_types {
 
 struct clear_refs_private {
 	enum clear_refs_types type;
+	unsigned long start, end;
+	bool clear_range;
 };
 
 #ifdef CONFIG_MEM_SOFT_DIRTY
@@ -1125,6 +1127,8 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
 	spinlock_t *ptl;
 	struct page *page;
 
+	BUG_ON(addr < cp->start || end > cp->end);
+
 	ptl = pmd_trans_huge_lock(pmd, vma);
 	if (ptl) {
 		if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
@@ -1181,9 +1185,11 @@ static int clear_refs_test_walk(unsigned long start, unsigned long end,
 	struct clear_refs_private *cp = walk->private;
 	struct vm_area_struct *vma = walk->vma;
 
-	if (vma->vm_flags & VM_PFNMAP)
+	if (!cp->clear_range && (vma->vm_flags & VM_PFNMAP))
 		return 1;
 
+	BUG_ON(start < cp->start || end > cp->end);
+
 	/*
 	 * Writing 1 to /proc/pid/clear_refs affects all pages.
 	 * Writing 2 to /proc/pid/clear_refs only affects anonymous pages.
@@ -1206,10 +1212,12 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 				size_t count, loff_t *ppos)
 {
 	struct task_struct *task;
-	char buffer[PROC_NUMBUF];
+	char buffer[18];
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
 	enum clear_refs_types type;
+	unsigned long start, end;
+	bool clear_range;
 	int itype;
 	int rv;
 
@@ -1218,12 +1226,34 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))
 		return -EFAULT;
-	rv = kstrtoint(strstrip(buffer), 10, &itype);
-	if (rv < 0)
-		return rv;
-	type = (enum clear_refs_types)itype;
-	if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST)
-		return -EINVAL;
+
+	if (buffer[0] == '6')
+	{
+		static int once;
+
+		if (!once++)
+			printk(KERN_DEBUG "task_mmu: Using POC clear refs range implementation.\n");
+
+		if (count != 17)
+			return -EINVAL;
+
+		type = CLEAR_REFS_SOFT_DIRTY;
+		start = *(unsigned long *)(buffer + 1);
+		end = *(unsigned long *)(buffer + 1 + 8);
+	}
+	else
+	{
+		rv = kstrtoint(strstrip(buffer), 10, &itype);
+		if (rv < 0)
+			return rv;
+		type = (enum clear_refs_types)itype;
+
+		if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST)
+			return -EINVAL;
+
+		start = 0;
+		end = -1UL;
+	}
 
 	task = get_proc_task(file_inode(file));
 	if (!task)
@@ -1235,41 +1265,87 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 			.type = type,
 		};
 
-		if (mmap_write_lock_killable(mm)) {
-			count = -EINTR;
-			goto out_mm;
+		if (start || end != -1UL)
+		{
+			start = min(start, mm->highest_vm_end) & PAGE_MASK;
+			end = min(end, mm->highest_vm_end) & PAGE_MASK;
+
+			if (start >= end)
+			{
+				count = -EINVAL;
+				goto out_mm;
+			}
+			clear_range = true;
 		}
+		else
+		{
+			clear_range = false;
+		}
+
+		cp.start = start;
+		cp.end = end;
+		cp.clear_range = clear_range;
+
 		if (type == CLEAR_REFS_MM_HIWATER_RSS) {
+			if (mmap_write_lock_killable(mm)) {
+				count = -EINTR;
+				goto out_mm;
+			}
+
 			/*
 			 * Writing 5 to /proc/pid/clear_refs resets the peak
 			 * resident set size to this mm's current rss value.
 			 */
 			reset_mm_hiwater_rss(mm);
-			goto out_unlock;
+			mmap_write_unlock(mm);
+			goto out_mm;
 		}
 
 		if (type == CLEAR_REFS_SOFT_DIRTY) {
-			for (vma = mm->mmap; vma; vma = vma->vm_next) {
-				if (!(vma->vm_flags & VM_SOFTDIRTY))
-					continue;
-				vma->vm_flags &= ~VM_SOFTDIRTY;
-				vma_set_page_prot(vma);
+			if (mmap_read_lock_killable(mm)) {
+				count = -EINTR;
+				goto out_mm;
 			}
-
+			if (!clear_range)
+				for (vma = mm->mmap; vma; vma = vma->vm_next) {
+				    if (!(vma->vm_flags & VM_SOFTDIRTY))
+					    continue;
+				    mmap_read_unlock(mm);
+				    if (mmap_write_lock_killable(mm)) {
+					    count = -EINTR;
+					    goto out_mm;
+				    }
+				    for (vma = mm->mmap; vma; vma = vma->vm_next) {
+					    vma->vm_flags &= ~VM_SOFTDIRTY;
+					    vma_set_page_prot(vma);
+				    }
+				    mmap_write_downgrade(mm);
+				    break;
+				}
 			inc_tlb_flush_pending(mm);
 			mmu_notifier_range_init(&range, MMU_NOTIFY_SOFT_DIRTY,
-						0, NULL, mm, 0, -1UL);
+						0, NULL, mm, start, end);
 			mmu_notifier_invalidate_range_start(&range);
 		}
-		walk_page_range(mm, 0, mm->highest_vm_end, &clear_refs_walk_ops,
+		else
+		{
+			if (mmap_write_lock_killable(mm)) {
+				count = -EINTR;
+				goto out_mm;
+			}
+		}
+		walk_page_range(mm, start, end == -1UL ? mm->highest_vm_end : end, &clear_refs_walk_ops,
 				&cp);
 		if (type == CLEAR_REFS_SOFT_DIRTY) {
 			mmu_notifier_invalidate_range_end(&range);
 			flush_tlb_mm(mm);
 			dec_tlb_flush_pending(mm);
+			mmap_read_unlock(mm);
+		}
+		else
+		{
+			mmap_write_unlock(mm);
 		}
-out_unlock:
-		mmap_write_unlock(mm);
 out_mm:
 		mmput(mm);
 	}
@@ -1301,6 +1377,7 @@ struct pagemapread {
 #define PM_PFRAME_MASK		GENMASK_ULL(PM_PFRAME_BITS - 1, 0)
 #define PM_SOFT_DIRTY		BIT_ULL(55)
 #define PM_MMAP_EXCLUSIVE	BIT_ULL(56)
+#define PM_SOFT_DIRTY_PAGE	BIT_ULL(57)
 #define PM_FILE			BIT_ULL(61)
 #define PM_SWAP			BIT_ULL(62)
 #define PM_PRESENT		BIT_ULL(63)
@@ -1373,11 +1450,11 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 		flags |= PM_PRESENT;
 		page = vm_normal_page(vma, addr, pte);
 		if (pte_soft_dirty(pte))
-			flags |= PM_SOFT_DIRTY;
+			flags |= PM_SOFT_DIRTY | PM_SOFT_DIRTY_PAGE;
 	} else if (is_swap_pte(pte)) {
 		swp_entry_t entry;
 		if (pte_swp_soft_dirty(pte))
-			flags |= PM_SOFT_DIRTY;
+			flags |= PM_SOFT_DIRTY | PM_SOFT_DIRTY_PAGE;
 		entry = pte_to_swp_entry(pte);
 		if (pm->show_pfn)
 			frame = swp_type(entry) |
@@ -1424,7 +1501,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
 
 			flags |= PM_PRESENT;
 			if (pmd_soft_dirty(pmd))
-				flags |= PM_SOFT_DIRTY;
+				flags |= PM_SOFT_DIRTY | PM_SOFT_DIRTY_PAGE;
 			if (pm->show_pfn)
 				frame = pmd_pfn(pmd) +
 					((addr & ~PMD_MASK) >> PAGE_SHIFT);
@@ -1442,7 +1519,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
 			}
 			flags |= PM_SWAP;
 			if (pmd_swp_soft_dirty(pmd))
-				flags |= PM_SOFT_DIRTY;
+				flags |= PM_SOFT_DIRTY | PM_SOFT_DIRTY_PAGE;
 			VM_BUG_ON(!is_pmd_migration_entry(pmd));
 			page = migration_entry_to_page(entry);
 		}
-- 
2.30.2

