21 files changed, 289 insertions, 212 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 9d2339a485c8..14b2bf2e5105 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -122,11 +122,18 @@ Description:
 		statistics (bd_count, bd_reads, bd_writes) in a format
 		similar to block layer statistics file format.
 
+What:		/sys/block/zram<id>/writeback_limit_enable
+Date:		November 2018
+Contact:	Minchan Kim <minchan@kernel.org>
+Description:
+		The writeback_limit_enable file is read-write and specifies
+		eanbe of writeback_limit feature. "1" means eable the feature.
+		No limit "0" is the initial state.
+
 What:		/sys/block/zram<id>/writeback_limit
 Date:		November 2018
 Contact:	Minchan Kim <minchan@kernel.org>
 Description:
 		The writeback_limit file is read-write and specifies the maximum
 		amount of writeback ZRAM can do. The limit could be changed
-		in run time and "0" means disable the limit.
-		No limit is the initial state.
+		in run time.
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 436c5e98e1b6..4df0ce271085 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -156,22 +156,23 @@ Per-device statistics are exported as various nodes under /sys/block/zram<id>/
 A brief description of exported device attributes. For more details please
 read Documentation/ABI/testing/sysfs-block-zram.
 
-Name            access            description
-----            ------            -----------
-disksize          RW    show and set the device's disk size
-initstate         RO    shows the initialization state of the device
-reset             WO    trigger device reset
-mem_used_max      WO    reset the `mem_used_max' counter (see later)
-mem_limit         WO    specifies the maximum amount of memory ZRAM can use
-                        to store the compressed data
-writeback_limit   WO    specifies the maximum amount of write IO zram can
-			write out to backing device as 4KB unit
-max_comp_streams  RW    the number of possible concurrent compress operations
-comp_algorithm    RW    show and change the compression algorithm
-compact           WO    trigger memory compaction
-debug_stat        RO    this file is used for zram debugging purposes
-backing_dev	  RW	set up backend storage for zram to write out
-idle		  WO	mark allocated slot as idle
+Name            	access            description
+----            	------            -----------
+disksize          	RW	show and set the device's disk size
+initstate         	RO	shows the initialization state of the device
+reset             	WO	trigger device reset
+mem_used_max      	WO	reset the `mem_used_max' counter (see later)
+mem_limit         	WO	specifies the maximum amount of memory ZRAM can use
+				to store the compressed data
+writeback_limit   	WO	specifies the maximum amount of write IO zram can
+				write out to backing device as 4KB unit
+writeback_limit_enable  RW	show and set writeback_limit feature
+max_comp_streams  	RW	the number of possible concurrent compress operations
+comp_algorithm    	RW	show and change the compression algorithm
+compact           	WO	trigger memory compaction
+debug_stat        	RO	this file is used for zram debugging purposes
+backing_dev	  	RW	set up backend storage for zram to write out
+idle		  	WO	mark allocated slot as idle
 
 
 User space is advised to use the following files to read the device statistics.
@@ -280,32 +281,51 @@ With the command, zram writeback idle pages from memory to the storage.
 If there are lots of write IO with flash device, potentially, it has
 flash wearout problem so that admin needs to design write limitation
 to guarantee storage health for entire product life.
-To overcome the concern, zram supports "writeback_limit".
-The "writeback_limit"'s default value is 0 so that it doesn't limit
-any writeback. If admin want to measure writeback count in a certain
-period, he could know it via /sys/block/zram0/bd_stat's 3rd column.
+
+To overcome the concern, zram supports "writeback_limit" feature.
+The "writeback_limit_enable"'s default value is 0 so that it doesn't limit
+any writeback. IOW, if admin want to apply writeback budget, he should
+enable writeback_limit_enable via
+
+	$ echo 1 > /sys/block/zramX/writeback_limit_enable
+
+Once writeback_limit_enable is set, zram doesn't allow any writeback
+until admin set the budget via /sys/block/zramX/writeback_limit.
+
+(If admin doesn't enable writeback_limit_enable, writeback_limit's value
+assigned via /sys/block/zramX/writeback_limit is meaninless.)
 
 If admin want to limit writeback as per-day 400M, he could do it
 like below.
 
-    MB_SHIFT=20
-    4K_SHIFT=12
-    echo $((400<<MB_SHIFT>>4K_SHIFT)) > \
-	    /sys/block/zram0/writeback_limit.
+	$ MB_SHIFT=20
+	$ 4K_SHIFT=12
+	$ echo $((400<<MB_SHIFT>>4K_SHIFT)) > \
+		/sys/block/zram0/writeback_limit.
+	$ echo 1 > /sys/block/zram0/writeback_limit_enable
 
-If admin want to allow further write again, he could do it like below
+If admin want to allow further write again once the bugdet is exausted,
+he could do it like below
 
-    echo 0 > /sys/block/zram0/writeback_limit
+	$ echo $((400<<MB_SHIFT>>4K_SHIFT)) > \
+		/sys/block/zram0/writeback_limit
 
 If admin want to see remaining writeback budget since he set,
 
-    cat /sys/block/zram0/writeback_limit
+	$ cat /sys/block/zramX/writeback_limit
+
+If admin want to disable writeback limit, he could do
+
+	$ echo 0 > /sys/block/zramX/writeback_limit_enable
 
 The writeback_limit count will reset whenever you reset zram(e.g.,
 system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of
 writeback happened until you reset the zram to allocate extra writeback
 budget in next setting is user's job.
 
+If admin want to measure writeback count in a certain period, he could
+know it via /sys/block/zram0/bd_stat's 3rd column.
+
 = memory tracking
 
 With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the
diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
index 13dd42c3ad4e..eb43e09c1980 100644
--- a/arch/arm64/include/asm/cache.h
+++ b/arch/arm64/include/asm/cache.h
@@ -58,6 +58,12 @@
  */
 #define ARCH_DMA_MINALIGN	(128)
 
+#ifdef CONFIG_KASAN_SW_TAGS
+#define ARCH_SLAB_MINALIGN	(1ULL << KASAN_SHADOW_SCALE_SHIFT)
+#else
+#define ARCH_SLAB_MINALIGN	__alignof__(unsigned long long)
+#endif
+
 #ifndef __ASSEMBLY__
 
 #include <linux/bitops.h>
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 33c5cc879f24..04ca65912638 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -316,11 +316,9 @@ static ssize_t idle_store(struct device *dev,
 		 * See the comment in writeback_store.
 		 */
 		zram_slot_lock(zram, index);
-		if (!zram_allocated(zram, index) ||
-				zram_test_flag(zram, index, ZRAM_UNDER_WB))
-			goto next;
-		zram_set_flag(zram, index, ZRAM_IDLE);
-next:
+		if (zram_allocated(zram, index) &&
+				!zram_test_flag(zram, index, ZRAM_UNDER_WB))
+			zram_set_flag(zram, index, ZRAM_IDLE);
 		zram_slot_unlock(zram, index);
 	}
 
@@ -330,6 +328,41 @@ next:
 }
 
 #ifdef CONFIG_ZRAM_WRITEBACK
+static ssize_t writeback_limit_enable_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct zram *zram = dev_to_zram(dev);
+	u64 val;
+	ssize_t ret = -EINVAL;
+
+	if (kstrtoull(buf, 10, &val))
+		return ret;
+
+	down_read(&zram->init_lock);
+	spin_lock(&zram->wb_limit_lock);
+	zram->wb_limit_enable = val;
+	spin_unlock(&zram->wb_limit_lock);
+	up_read(&zram->init_lock);
+	ret = len;
+
+	return ret;
+}
+
+static ssize_t writeback_limit_enable_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	bool val;
+	struct zram *zram = dev_to_zram(dev);
+
+	down_read(&zram->init_lock);
+	spin_lock(&zram->wb_limit_lock);
+	val = zram->wb_limit_enable;
+	spin_unlock(&zram->wb_limit_lock);
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+
 static ssize_t writeback_limit_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
@@ -341,9 +374,9 @@ static ssize_t writeback_limit_store(struct device *dev,
 		return ret;
 
 	down_read(&zram->init_lock);
-	atomic64_set(&zram->stats.bd_wb_limit, val);
-	if (val == 0)
-		zram->stop_writeback = false;
+	spin_lock(&zram->wb_limit_lock);
+	zram->bd_wb_limit = val;
+	spin_unlock(&zram->wb_limit_lock);
 	up_read(&zram->init_lock);
 	ret = len;
 
@@ -357,7 +390,9 @@ static ssize_t writeback_limit_show(struct device *dev,
 	struct zram *zram = dev_to_zram(dev);
 
 	down_read(&zram->init_lock);
-	val = atomic64_read(&zram->stats.bd_wb_limit);
+	spin_lock(&zram->wb_limit_lock);
+	val = zram->bd_wb_limit;
+	spin_unlock(&zram->wb_limit_lock);
 	up_read(&zram->init_lock);
 
 	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
@@ -588,8 +623,8 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
 	return 1;
 }
 
-#define HUGE_WRITEBACK 0x1
-#define IDLE_WRITEBACK 0x2
+#define HUGE_WRITEBACK 1
+#define IDLE_WRITEBACK 2
 
 static ssize_t writeback_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
@@ -602,7 +637,7 @@ static ssize_t writeback_store(struct device *dev,
 	struct page *page;
 	ssize_t ret, sz;
 	char mode_buf[8];
-	unsigned long mode = -1UL;
+	int mode = -1;
 	unsigned long blk_idx = 0;
 
 	sz = strscpy(mode_buf, buf, sizeof(mode_buf));
@@ -618,7 +653,7 @@ static ssize_t writeback_store(struct device *dev,
 	else if (!strcmp(mode_buf, "huge"))
 		mode = HUGE_WRITEBACK;
 
-	if (mode == -1UL)
+	if (mode == -1)
 		return -EINVAL;
 
 	down_read(&zram->init_lock);
@@ -645,10 +680,13 @@ static ssize_t writeback_store(struct device *dev,
 		bvec.bv_len = PAGE_SIZE;
 		bvec.bv_offset = 0;
 
-		if (zram->stop_writeback) {
+		spin_lock(&zram->wb_limit_lock);
+		if (zram->wb_limit_enable && !zram->bd_wb_limit) {
+			spin_unlock(&zram->wb_limit_lock);
 			ret = -EIO;
 			break;
 		}
+		spin_unlock(&zram->wb_limit_lock);
 
 		if (!blk_idx) {
 			blk_idx = alloc_block_bdev(zram);
@@ -667,10 +705,11 @@ static ssize_t writeback_store(struct device *dev,
 				zram_test_flag(zram, index, ZRAM_UNDER_WB))
 			goto next;
 
-		if ((mode & IDLE_WRITEBACK &&
-			  !zram_test_flag(zram, index, ZRAM_IDLE)) &&
-		    (mode & HUGE_WRITEBACK &&
-			  !zram_test_flag(zram, index, ZRAM_HUGE)))
+		if (mode == IDLE_WRITEBACK &&
+			  !zram_test_flag(zram, index, ZRAM_IDLE))
+			goto next;
+		if (mode == HUGE_WRITEBACK &&
+			  !zram_test_flag(zram, index, ZRAM_HUGE))
 			goto next;
 		/*
 		 * Clearing ZRAM_UNDER_WB is duty of caller.
@@ -732,11 +771,10 @@ static ssize_t writeback_store(struct device *dev,
 		zram_set_element(zram, index, blk_idx);
 		blk_idx = 0;
 		atomic64_inc(&zram->stats.pages_stored);
-		if (atomic64_add_unless(&zram->stats.bd_wb_limit,
-					-1 << (PAGE_SHIFT - 12), 0)) {
-			if (atomic64_read(&zram->stats.bd_wb_limit) == 0)
-				zram->stop_writeback = true;
-		}
+		spin_lock(&zram->wb_limit_lock);
+		if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
+			zram->bd_wb_limit -=  1UL << (PAGE_SHIFT - 12);
+		spin_unlock(&zram->wb_limit_lock);
 next:
 		zram_slot_unlock(zram, index);
 	}
@@ -1812,6 +1850,7 @@ static DEVICE_ATTR_RW(comp_algorithm);
 static DEVICE_ATTR_RW(backing_dev);
 static DEVICE_ATTR_WO(writeback);
 static DEVICE_ATTR_RW(writeback_limit);
+static DEVICE_ATTR_RW(writeback_limit_enable);
 #endif
 
 static struct attribute *zram_disk_attrs[] = {
@@ -1828,6 +1867,7 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_backing_dev.attr,
 	&dev_attr_writeback.attr,
 	&dev_attr_writeback_limit.attr,
+	&dev_attr_writeback_limit_enable.attr,
 #endif
 	&dev_attr_io_stat.attr,
 	&dev_attr_mm_stat.attr,
@@ -1867,7 +1907,9 @@ static int zram_add(void)
 	device_id = ret;
 
 	init_rwsem(&zram->init_lock);
-
+#ifdef CONFIG_ZRAM_WRITEBACK
+	spin_lock_init(&zram->wb_limit_lock);
+#endif
 	queue = blk_alloc_queue(GFP_KERNEL);
 	if (!queue) {
 		pr_err("Error allocating disk queue for device %d\n",
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 4bd3afd15e83..f2fd46daa760 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -86,7 +86,6 @@ struct zram_stats {
 	atomic64_t bd_count;		/* no. of pages in backing device */
 	atomic64_t bd_reads;		/* no. of reads from backing device */
 	atomic64_t bd_writes;		/* no. of writes from backing device */
-	atomic64_t bd_wb_limit;		/* writeback limit of backing device */
 #endif
 };
 
@@ -114,8 +113,10 @@ struct zram {
 	 */
 	bool claim; /* Protected by bdev->bd_mutex */
 	struct file *backing_dev;
-	bool stop_writeback;
 #ifdef CONFIG_ZRAM_WRITEBACK
+	spinlock_t wb_limit_lock;
+	bool wb_limit_enable;
+	u64 bd_wb_limit;
 	struct block_device *bdev;
 	unsigned int old_block_size;
 	unsigned long *bitmap;
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index a2fcea5f8225..32920a10100e 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -383,16 +383,17 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end)
  * truncation is indicated by end of range being LLONG_MAX
  *	In this case, we first scan the range and release found pages.
  *	After releasing pages, hugetlb_unreserve_pages cleans up region/reserv
- *	maps and global counts.
+ *	maps and global counts.  Page faults can not race with truncation
+ *	in this routine.  hugetlb_no_page() prevents page faults in the
+ *	truncated range.  It checks i_size before allocation, and again after
+ *	with the page table lock for the page held.  The same lock must be
+ *	acquired to unmap a page.
  * hole punch is indicated if end is not LLONG_MAX
  *	In the hole punch case we scan the range and release found pages.
  *	Only when releasing a page is the associated region/reserv map
  *	deleted.  The region/reserv map for ranges without associated
- *	pages are not modified.
- *
- * Callers of this routine must hold the i_mmap_rwsem in write mode to prevent
- * races with page faults.
- *
+ *	pages are not modified.  Page faults can race with hole punch.
+ *	This is indicated if we find a mapped page.
  * Note: If the passed end of range value is beyond the end of file, but
  * not LLONG_MAX this routine still performs a hole punch operation.
  */
@@ -422,14 +423,32 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
 
 		for (i = 0; i < pagevec_count(&pvec); ++i) {
 			struct page *page = pvec.pages[i];
+			u32 hash;
 
 			index = page->index;
+			hash = hugetlb_fault_mutex_hash(h, current->mm,
+							&pseudo_vma,
+							mapping, index, 0);
+			mutex_lock(&hugetlb_fault_mutex_table[hash]);
+
 			/*
-			 * A mapped page is impossible as callers should unmap
-			 * all references before calling.  And, i_mmap_rwsem
-			 * prevents the creation of additional mappings.
+			 * If page is mapped, it was faulted in after being
+			 * unmapped in caller.  Unmap (again) now after taking
+			 * the fault mutex.  The mutex will prevent faults
+			 * until we finish removing the page.
+			 *
+			 * This race can only happen in the hole punch case.
+			 * Getting here in a truncate operation is a bug.
 			 */
-			VM_BUG_ON(page_mapped(page));
+			if (unlikely(page_mapped(page))) {
+				BUG_ON(truncate_op);
+
+				i_mmap_lock_write(mapping);
+				hugetlb_vmdelete_list(&mapping->i_mmap,
+					index * pages_per_huge_page(h),
+					(index + 1) * pages_per_huge_page(h));
+				i_mmap_unlock_write(mapping);
+			}
 
 			lock_page(page);
 			/*
@@ -451,6 +470,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
 			}
 
 			unlock_page(page);
+			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 		}
 		huge_pagevec_release(&pvec);
 		cond_resched();
@@ -462,20 +482,9 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
 
 static void hugetlbfs_evict_inode(struct inode *inode)
 {
-	struct address_space *mapping = inode->i_mapping;
 	struct resv_map *resv_map;
 
-	/*
-	 * The vfs layer guarantees that there are no other users of this
-	 * inode.  Therefore, it would be safe to call remove_inode_hugepages
-	 * without holding i_mmap_rwsem.  We acquire and hold here to be
-	 * consistent with other callers.  Since there will be no contention
-	 * on the semaphore, overhead is negligible.
-	 */
-	i_mmap_lock_write(mapping);
 	remove_inode_hugepages(inode, 0, LLONG_MAX);
-	i_mmap_unlock_write(mapping);
-
 	resv_map = (struct resv_map *)inode->i_mapping->private_data;
 	/* root inode doesn't have the resv_map, so we should check it */
 	if (resv_map)
@@ -496,8 +505,8 @@ static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
 	i_mmap_lock_write(mapping);
 	if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
 		hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0);
-	remove_inode_hugepages(inode, offset, LLONG_MAX);
 	i_mmap_unlock_write(mapping);
+	remove_inode_hugepages(inode, offset, LLONG_MAX);
 	return 0;
 }
 
@@ -531,8 +540,8 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 			hugetlb_vmdelete_list(&mapping->i_mmap,
 						hole_start >> PAGE_SHIFT,
 						hole_end  >> PAGE_SHIFT);
-		remove_inode_hugepages(inode, hole_start, hole_end);
 		i_mmap_unlock_write(mapping);
+		remove_inode_hugepages(inode, hole_start, hole_end);
 		inode_unlock(inode);
 	}
 
@@ -615,11 +624,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
 		/* addr is the offset within the file (zero based) */
 		addr = index * hpage_size;
 
-		/*
-		 * fault mutex taken here, protects against fault path
-		 * and hole punch.  inode_lock previously taken protects
-		 * against truncation.
-		 */
+		/* mutex taken here, fault path and hole punch */
 		hash = hugetlb_fault_mutex_hash(h, mm, &pseudo_vma, mapping,
 						index, addr);
 		mutex_lock(&hugetlb_fault_mutex_table[hash]);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index cc4a507d7ca4..842f9189537b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -520,6 +520,12 @@ enum pgdat_flags {
 	PGDAT_RECLAIM_LOCKED,		/* prevents concurrent reclaim */
 };
 
+enum zone_flags {
+	ZONE_BOOSTED_WATERMARK,		/* zone recently boosted watermarks.
+					 * Cleared when kswapd is woken.
+					 */
+};
+
 static inline unsigned long zone_managed_pages(struct zone *zone)
 {
 	return (unsigned long)atomic_long_read(&zone->managed_pages);
diff --git a/kernel/fork.c b/kernel/fork.c
index 7f49be94eba9..b69248e6f0e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -217,6 +217,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 		memset(s->addr, 0, THREAD_SIZE);
 
 		tsk->stack_vm_area = s;
+		tsk->stack = s->addr;
 		return s->addr;
 	}
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 745088810965..df2e7dd5ff17 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3238,7 +3238,6 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 	struct page *ptepage;
 	unsigned long addr;
 	int cow;
-	struct address_space *mapping = vma->vm_file->f_mapping;
 	struct hstate *h = hstate_vma(vma);
 	unsigned long sz = huge_page_size(h);
 	struct mmu_notifier_range range;
@@ -3250,23 +3249,13 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 		mmu_notifier_range_init(&range, src, vma->vm_start,
 					vma->vm_end);
 		mmu_notifier_invalidate_range_start(&range);
-	} else {
-		/*
-		 * For shared mappings i_mmap_rwsem must be held to call
-		 * huge_pte_alloc, otherwise the returned ptep could go
-		 * away if part of a shared pmd and another thread calls
-		 * huge_pmd_unshare.
-		 */
-		i_mmap_lock_read(mapping);
 	}
 
 	for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
 		spinlock_t *src_ptl, *dst_ptl;
-
 		src_pte = huge_pte_offset(src, addr, sz);
 		if (!src_pte)
 			continue;
-
 		dst_pte = huge_pte_alloc(dst, addr, sz);
 		if (!dst_pte) {
 			ret = -ENOMEM;
@@ -3337,8 +3326,6 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 
 	if (cow)
 		mmu_notifier_invalidate_range_end(&range);
-	else
-		i_mmap_unlock_read(mapping);
 
 	return ret;
 }
@@ -3755,16 +3742,16 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
 	}
 
 	/*
-	 * We can not race with truncation due to holding i_mmap_rwsem.
-	 * Check once here for faults beyond end of file.
+	 * Use page lock to guard against racing truncation
+	 * before we get page_table_lock.
 	 */
-	size = i_size_read(mapping->host) >> huge_page_shift(h);
-	if (idx >= size)
-		goto out;
-
 retry:
 	page = find_lock_page(mapping, idx);
 	if (!page) {
+		size = i_size_read(mapping->host) >> huge_page_shift(h);
+		if (idx >= size)
+			goto out;
+
 		/*
 		 * Check for page in userfault range
 		 */
@@ -3784,18 +3771,14 @@ retry:
 			};
 
 			/*
-			 * hugetlb_fault_mutex and i_mmap_rwsem must be
-			 * dropped before handling userfault.  Reacquire
-			 * after handling fault to make calling code simpler.
+			 * hugetlb_fault_mutex must be dropped before
+			 * handling userfault.  Reacquire after handling
+			 * fault to make calling code simpler.
 			 */
 			hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping,
 							idx, haddr);
 			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
-			i_mmap_unlock_read(mapping);
-
 			ret = handle_userfault(&vmf, VM_UFFD_MISSING);
-
-			i_mmap_lock_read(mapping);
 			mutex_lock(&hugetlb_fault_mutex_table[hash]);
 			goto out;
 		}
@@ -3854,6 +3837,9 @@ retry:
 	}
 
 	ptl = huge_pte_lock(h, mm, ptep);
+	size = i_size_read(mapping->host) >> huge_page_shift(h);
+	if (idx >= size)
+		goto backout;
 
 	ret = 0;
 	if (!huge_pte_none(huge_ptep_get(ptep)))
@@ -3940,11 +3926,6 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 
 	ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
 	if (ptep) {
-		/*
-		 * Since we hold no locks, ptep could be stale.  That is
-		 * OK as we are only making decisions based on content and
-		 * not actually modifying content here.
-		 */
 		entry = huge_ptep_get(ptep);
 		if (unlikely(is_hugetlb_entry_migration(entry))) {
 			migration_entry_wait_huge(vma, mm, ptep);
@@ -3952,33 +3933,20 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
 			return VM_FAULT_HWPOISON_LARGE |
 				VM_FAULT_SET_HINDEX(hstate_index(h));
+	} else {
+		ptep = huge_pte_alloc(mm, haddr, huge_page_size(h));
+		if (!ptep)
+			return VM_FAULT_OOM;
 	}
 
-	/*
-	 * Acquire i_mmap_rwsem before calling huge_pte_alloc and hold
-	 * until finished with ptep.  This serves two purposes:
-	 * 1) It prevents huge_pmd_unshare from being called elsewhere
-	 *    and making the ptep no longer valid.
-	 * 2) It synchronizes us with file truncation.
-	 *
-	 * ptep could have already be assigned via huge_pte_offset.  That
-	 * is OK, as huge_pte_alloc will return the same value unless
-	 * something changed.
-	 */
 	mapping = vma->vm_file->f_mapping;
-	i_mmap_lock_read(mapping);
-	ptep = huge_pte_alloc(mm, haddr, huge_page_size(h));
-	if (!ptep) {
-		i_mmap_unlock_read(mapping);
-		return VM_FAULT_OOM;
-	}
+	idx = vma_hugecache_offset(h, vma, haddr);
 
 	/*
 	 * Serialize hugepage allocation and instantiation, so that we don't
 	 * get spurious allocation failures if two CPUs race to instantiate
 	 * the same page in the page cache.
 	 */
-	idx = vma_hugecache_offset(h, vma, haddr);
 	hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping, idx, haddr);
 	mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
@@ -4066,7 +4034,6 @@ out_ptl:
 	}
 out_mutex:
 	mutex_unlock(&hugetlb_fault_mutex_table[hash]);
-	i_mmap_unlock_read(mapping);
 	/*
 	 * Generally it's safe to hold refcount during waiting page lock. But
 	 * here we just wait to defer the next page fault to avoid busy loop and
@@ -4671,12 +4638,10 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
  * and returns the corresponding pte. While this is not necessary for the
  * !shared pmd case because we can allocate the pmd later as well, it makes the
- * code much cleaner.
- *
- * This routine must be called with i_mmap_rwsem held in at least read mode.
- * For hugetlbfs, this prevents removal of any page table entries associated
- * with the address space.  This is important as we are setting up sharing
- * based on existing page table entries (mappings).
+ * code much cleaner. pmd allocation is essential for the shared case because
+ * pud has to be populated inside the same i_mmap_rwsem section - otherwise
+ * racing tasks could either miss the sharing (see huge_pte_offset) or select a
+ * bad pmd for sharing.
  */
 pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
 {
@@ -4693,6 +4658,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
 	if (!vma_shareable(vma, addr))
 		return (pte_t *)pmd_alloc(mm, pud, addr);
 
+	i_mmap_lock_write(mapping);
 	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
 		if (svma == vma)
 			continue;
@@ -4722,6 +4688,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
 	spin_unlock(ptl);
 out:
 	pte = (pte_t *)pmd_alloc(mm, pud, addr);
+	i_mmap_unlock_write(mapping);
 	return pte;
 }
 
@@ -4732,7 +4699,7 @@ out:
  * indicated by page_count > 1, unmap is achieved by clearing pud and
  * decrementing the ref count. If count == 1, the pte page is not shared.
  *
- * Called with page table lock held and i_mmap_rwsem held in write mode.
+ * called with page table lock held.
  *
  * returns: 1 successfully unmapped a shared pte page
  *	    0 the underlying pte page is not shared, or it is the last user
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 03d5d1374ca7..73c9cbfdedf4 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -298,8 +298,6 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 		return;
 	}
 
-	cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
-
 	*flags |= SLAB_KASAN;
 }
 
@@ -349,28 +347,43 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 }
 
 /*
- * Since it's desirable to only call object contructors once during slab
- * allocation, we preassign tags to all such objects. Also preassign tags for
- * SLAB_TYPESAFE_BY_RCU slabs to avoid use-after-free reports.
- * For SLAB allocator we can't preassign tags randomly since the freelist is
- * stored as an array of indexes instead of a linked list. Assign tags based
- * on objects indexes, so that objects that are next to each other get
- * different tags.
- * After a tag is assigned, the object always gets allocated with the same tag.
- * The reason is that we can't change tags for objects with constructors on
- * reallocation (even for non-SLAB_TYPESAFE_BY_RCU), because the constructor
- * code can save the pointer to the object somewhere (e.g. in the object
- * itself). Then if we retag it, the old saved pointer will become invalid.
+ * This function assigns a tag to an object considering the following:
+ * 1. A cache might have a constructor, which might save a pointer to a slab
+ *    object somewhere (e.g. in the object itself). We preassign a tag for
+ *    each object in caches with constructors during slab creation and reuse
+ *    the same tag each time a particular object is allocated.
+ * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
+ *    accessed after being freed. We preassign tags for objects in these
+ *    caches as well.
+ * 3. For SLAB allocator we can't preassign tags randomly since the freelist
+ *    is stored as an array of indexes instead of a linked list. Assign tags
+ *    based on objects indexes, so that objects that are next to each other
+ *    get different tags.
  */
-static u8 assign_tag(struct kmem_cache *cache, const void *object, bool new)
+static u8 assign_tag(struct kmem_cache *cache, const void *object,
+			bool init, bool krealloc)
 {
+	/* Reuse the same tag for krealloc'ed objects. */
+	if (krealloc)
+		return get_tag(object);
+
+	/*
+	 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
+	 * set, assign a tag when the object is being allocated (init == false).
+	 */
 	if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
-		return new ? KASAN_TAG_KERNEL : random_tag();
+		return init ? KASAN_TAG_KERNEL : random_tag();
 
+	/* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
 #ifdef CONFIG_SLAB
+	/* For SLAB assign tags based on the object index in the freelist. */
 	return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
 #else
-	return new ? random_tag() : get_tag(object);
+	/*
+	 * For SLUB assign a random tag during slab creation, otherwise reuse
+	 * the already assigned tag.
+	 */
+	return init ? random_tag() : get_tag(object);
 #endif
 }
 
@@ -386,7 +399,8 @@ void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
 	__memset(alloc_info, 0, sizeof(*alloc_info));
 
 	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
-		object = set_tag(object, assign_tag(cache, object, true));
+		object = set_tag(object,
+				assign_tag(cache, object, true, false));
 
 	return (void *)object;
 }
@@ -452,8 +466,8 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
 	return __kasan_slab_free(cache, object, ip, true);
 }
 
-void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
-					size_t size, gfp_t flags)
+static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
+				size_t size, gfp_t flags, bool krealloc)
 {
 	unsigned long redzone_start;
 	unsigned long redzone_end;
@@ -471,7 +485,7 @@ void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
 				KASAN_SHADOW_SCALE_SIZE);
 
 	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
-		tag = assign_tag(cache, object, false);
+		tag = assign_tag(cache, object, false, krealloc);
 
 	/* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
 	kasan_unpoison_shadow(set_tag(object, tag), size);
@@ -483,6 +497,12 @@ void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
 
 	return set_tag(object, tag);
 }
+
+void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
+				size_t size, gfp_t flags)
+{
+	return __kasan_kmalloc(cache, object, size, flags, false);
+}
 EXPORT_SYMBOL(kasan_kmalloc);
 
 void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
@@ -522,7 +542,8 @@ void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
 	if (unlikely(!PageSlab(page)))
 		return kasan_kmalloc_large(object, size, flags);
 	else
-		return kasan_kmalloc(page->slab_cache, object, size, flags);
+		return __kasan_kmalloc(page->slab_cache, object, size,
+						flags, true);
 }
 
 void kasan_poison_kfree(void *ptr, unsigned long ip)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 6379fff1a5ff..7c72f2a95785 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -966,7 +966,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
 	struct address_space *mapping;
 	LIST_HEAD(tokill);
-	bool unmap_success = true;
+	bool unmap_success;
 	int kill = 1, forcekill;
 	struct page *hpage = *hpagep;
 	bool mlocked = PageMlocked(hpage);
@@ -1028,19 +1028,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	if (kill)
 		collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
 
-	if (!PageHuge(hpage)) {
-		unmap_success = try_to_unmap(hpage, ttu);
-	} else if (mapping) {
-		/*
-		 * For hugetlb pages, try_to_unmap could potentially call
-		 * huge_pmd_unshare.  Because of this, take semaphore in
-		 * write mode here and set TTU_RMAP_LOCKED to indicate we
-		 * have taken the lock at this higer level.
-		 */
-		i_mmap_lock_write(mapping);
-		unmap_success = try_to_unmap(hpage, ttu|TTU_RMAP_LOCKED);
-		i_mmap_unlock_write(mapping);
-	}
+	unmap_success = try_to_unmap(hpage, ttu);
 	if (!unmap_success)
 		pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
 		       pfn, page_mapcount(hpage));
diff --git a/mm/memory.c b/mm/memory.c
index a52663c0612d..e11ca9dd823f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2994,6 +2994,28 @@ static vm_fault_t __do_fault(struct vm_fault *vmf)
 	struct vm_area_struct *vma = vmf->vma;
 	vm_fault_t ret;
 
+	/*
+	 * Preallocate pte before we take page_lock because this might lead to
+	 * deadlocks for memcg reclaim which waits for pages under writeback:
+	 *				lock_page(A)
+	 *				SetPageWriteback(A)
+	 *				unlock_page(A)
+	 * lock_page(B)
+	 *				lock_page(B)
+	 * pte_alloc_pne
+	 *   shrink_page_list
+	 *     wait_on_page_writeback(A)
+	 *				SetPageWriteback(B)
+	 *				unlock_page(B)
+	 *				# flush A, B to clear the writeback
+	 */
+	if (pmd_none(*vmf->pmd) && !vmf->prealloc_pte) {
+		vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm);
+		if (!vmf->prealloc_pte)
+			return VM_FAULT_OOM;
+		smp_wmb(); /* See comment in __pte_alloc() */
+	}
+
 	ret = vma->vm_ops->fault(vmf);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
 			    VM_FAULT_DONE_COW)))
@@ -4077,8 +4099,8 @@ static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 		goto out;
 
 	if (range) {
-		range->start = address & PAGE_MASK;
-		range->end = range->start + PAGE_SIZE;
+		mmu_notifier_range_init(range, mm, address & PAGE_MASK,
+				     (address & PAGE_MASK) + PAGE_SIZE);
 		mmu_notifier_invalidate_range_start(range);
 	}
 	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
diff --git a/mm/migrate.c b/mm/migrate.c
index ccf8966caf6f..a16b15090df3 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1324,19 +1324,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 		goto put_anon;
 
 	if (page_mapped(hpage)) {
-		struct address_space *mapping = page_mapping(hpage);
-
-		/*
-		 * try_to_unmap could potentially call huge_pmd_unshare.
-		 * Because of this, take semaphore in write mode here and
-		 * set TTU_RMAP_LOCKED to let lower levels know we have
-		 * taken the lock.
-		 */
-		i_mmap_lock_write(mapping);
 		try_to_unmap(hpage,
-			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS|
-			TTU_RMAP_LOCKED);
-		i_mmap_unlock_write(mapping);
+			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
 		page_was_mapped = 1;
 	}
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cde5dac6229a..d295c9bc01a8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2214,7 +2214,7 @@ static void steal_suitable_fallback(struct zone *zone, struct page *page,
 	 */
 	boost_watermark(zone);
 	if (alloc_flags & ALLOC_KSWAPD)
-		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
+		set_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
 
 	/* We are not allowed to try stealing from the whole block */
 	if (!whole_block)
@@ -3102,6 +3102,12 @@ struct page *rmqueue(struct zone *preferred_zone,
 	local_irq_restore(flags);
 
 out:
+	/* Separate test+clear to avoid unnecessary atomics */
+	if (test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags)) {
+		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
+		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
+	}
+
 	VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
 	return page;
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 21a26cf51114..68a1a5b869a5 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -25,7 +25,6 @@
  *     page->flags PG_locked (lock_page)
  *       hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share)
  *         mapping->i_mmap_rwsem
- *           hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
  *           anon_vma->rwsem
  *             mm->page_table_lock or pte_lock
  *               zone_lru_lock (in mark_page_accessed, isolate_lru_page)
@@ -1379,9 +1378,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 		/*
 		 * If sharing is possible, start and end will be adjusted
 		 * accordingly.
-		 *
-		 * If called for a huge page, caller must hold i_mmap_rwsem
-		 * in write mode as it is possible to call huge_pmd_unshare.
 		 */
 		adjust_range_if_pmd_sharing_possible(vma, &range.start,
 						     &range.end);
diff --git a/mm/slab.c b/mm/slab.c
index 73fe23e649c9..78eb8c5bf4e4 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -666,8 +666,10 @@ static struct alien_cache *__alloc_alien_cache(int node, int entries,
 	struct alien_cache *alc = NULL;
 
 	alc = kmalloc_node(memsize, gfp, node);
-	init_arraycache(&alc->ac, entries, batch);
-	spin_lock_init(&alc->lock);
+	if (alc) {
+		init_arraycache(&alc->ac, entries, batch);
+		spin_lock_init(&alc->lock);
+	}
 	return alc;
 }
 
diff --git a/mm/slub.c b/mm/slub.c
index 36c0befeebd8..1e3d0ec4e200 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3846,6 +3846,8 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
 	unsigned int offset;
 	size_t object_size;
 
+	ptr = kasan_reset_tag(ptr);
+
 	/* Find object and usable object size. */
 	s = page->slab_cache;
 
diff --git a/mm/usercopy.c b/mm/usercopy.c
index 852eb4e53f06..14faadcedd06 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -247,7 +247,8 @@ static DEFINE_STATIC_KEY_FALSE_RO(bypass_usercopy_checks);
 /*
  * Validates that the given object is:
  * - not bogus address
- * - known-safe heap or stack object
+ * - fully contained by stack (or stack frame, when available)
+ * - fully within SLAB object (or object whitelist area, when available)
  * - not in kernel text
  */
 void __check_object_size(const void *ptr, unsigned long n, bool to_user)
@@ -262,9 +263,6 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user)
 	/* Check for invalid addresses. */
 	check_bogus_address((const unsigned long)ptr, n, to_user);
 
-	/* Check for bad heap object. */
-	check_heap_object(ptr, n, to_user);
-
 	/* Check for bad stack object. */
 	switch (check_stack_object(ptr, n)) {
 	case NOT_STACK:
@@ -282,6 +280,9 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user)
 		usercopy_abort("process stack", NULL, to_user, 0, n);
 	}
 
+	/* Check for bad heap object. */
+	check_heap_object(ptr, n, to_user);
+
 	/* Check for object in kernel to avoid text exposure. */
 	check_kernel_text_object((const unsigned long)ptr, n, to_user);
 }
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 065c1ce191c4..d59b5a73dfb3 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -267,14 +267,10 @@ retry:
 		VM_BUG_ON(dst_addr & ~huge_page_mask(h));
 
 		/*
-		 * Serialize via i_mmap_rwsem and hugetlb_fault_mutex.
-		 * i_mmap_rwsem ensures the dst_pte remains valid even
-		 * in the case of shared pmds.  fault mutex prevents
-		 * races with other faulting threads.
+		 * Serialize via hugetlb_fault_mutex
 		 */
-		mapping = dst_vma->vm_file->f_mapping;
-		i_mmap_lock_read(mapping);
 		idx = linear_page_index(dst_vma, dst_addr);
+		mapping = dst_vma->vm_file->f_mapping;
 		hash = hugetlb_fault_mutex_hash(h, dst_mm, dst_vma, mapping,
 								idx, dst_addr);
 		mutex_lock(&hugetlb_fault_mutex_table[hash]);
@@ -283,7 +279,6 @@ retry:
 		dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h));
 		if (!dst_pte) {
 			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
-			i_mmap_unlock_read(mapping);
 			goto out_unlock;
 		}
 
@@ -291,7 +286,6 @@ retry:
 		dst_pteval = huge_ptep_get(dst_pte);
 		if (!huge_pte_none(dst_pteval)) {
 			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
-			i_mmap_unlock_read(mapping);
 			goto out_unlock;
 		}
 
@@ -299,7 +293,6 @@ retry:
 						dst_addr, src_addr, &page);
 
 		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
-		i_mmap_unlock_read(mapping);
 		vm_alloc_shared = vm_shared;
 
 		cond_resched();
diff --git a/mm/util.c b/mm/util.c
index 4df23d64aac7..1ea055138043 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -478,7 +478,7 @@ bool page_mapped(struct page *page)
 		return true;
 	if (PageHuge(page))
 		return false;
-	for (i = 0; i < hpage_nr_pages(page); i++) {
+	for (i = 0; i < (1 << compound_order(page)); i++) {
 		if (atomic_read(&page[i]._mapcount) >= 0)
 			return true;
 	}
diff --git a/tools/vm/page_owner_sort.c b/tools/vm/page_owner_sort.c
index 18fc112b65cd..d3a8755c039c 100644
--- a/tools/vm/page_owner_sort.c
+++ b/tools/vm/page_owner_sort.c
@@ -5,7 +5,9 @@
  * Example use:
  * cat /sys/kernel/debug/page_owner > page_owner_full.txt
  * grep -v ^PFN page_owner_full.txt > page_owner.txt
- * ./sort page_owner.txt sorted_page_owner.txt
+ * ./page_owner_sort page_owner.txt sorted_page_owner.txt
+ *
+ * See Documentation/vm/page_owner.rst
 */
 
 #include <stdio.h>