Merge branch 'akpm' (patches from Andrew)

Merge misc fixes from Andrew Morton:
 "14 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm, page_alloc: do not wake kswapd with zone lock held
  hugetlbfs: revert "use i_mmap_rwsem for more pmd sharing synchronization"
  hugetlbfs: revert "Use i_mmap_rwsem to fix page fault/truncate race"
  mm: page_mapped: don't assume compound page is huge or THP
  mm/memory.c: initialise mmu_notifier_range correctly
  tools/vm/page_owner: use page_owner_sort in the use example
  kasan: fix krealloc handling for tag-based mode
  kasan: make tag based mode work with CONFIG_HARDENED_USERCOPY
  kasan, arm64: use ARCH_SLAB_MINALIGN instead of manual aligning
  mm, memcg: fix reclaim deadlock with writeback
  mm/usercopy.c: no check page span for stack objects
  slab: alien caches must not be initialized if the allocation of the alien cache failed
  fork, memcg: fix cached_stacks case
  zram: idle writeback fixes and cleanup

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.

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

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>

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 @@ static ssize_t idle_store(struct device *dev,
 }
 
 #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",

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;