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authorMinchan Kim <minchan@kernel.org>2018-12-28 11:36:54 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-28 23:11:49 +0300
commitbb416d18b850faaa44bd3bb67c9728922c3cce98 (patch)
tree112f74c2842e9e2565911546cb0ff69c407ad393 /drivers/block
parent23eddf39b2c28c05cb8f8203d38e61807d701b38 (diff)
downloadlinux-bb416d18b850faaa44bd3bb67c9728922c3cce98.tar.xz
zram: writeback throttle
If there are lots of write IO with flash device, it could have a wearout problem of storage. To overcome the problem, admin needs to design write limitation to guarantee flash health for entire product life. This patch creates a new knob "writeback_limit" for zram. 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. 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. If admin want to allow further write again, he could do it like below echo 0 > /sys/block/zram0/writeback_limit If admin want to see remaining writeback budget, cat /sys/block/zram0/writeback_limit 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. [minchan@kernel.org: v4] Link: http://lkml.kernel.org/r/20181203024045.153534-8-minchan@kernel.org Link: http://lkml.kernel.org/r/20181127055429.251614-8-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Joey Pabalinas <joeypabalinas@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/zram/zram_drv.c52
-rw-r--r--drivers/block/zram/zram_drv.h2
2 files changed, 51 insertions, 3 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index f1832fa3ba41..33c5cc879f24 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -330,6 +330,39 @@ next:
}
#ifdef CONFIG_ZRAM_WRITEBACK
+static ssize_t writeback_limit_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);
+ atomic64_set(&zram->stats.bd_wb_limit, val);
+ if (val == 0)
+ zram->stop_writeback = false;
+ up_read(&zram->init_lock);
+ ret = len;
+
+ return ret;
+}
+
+static ssize_t writeback_limit_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ u64 val;
+ struct zram *zram = dev_to_zram(dev);
+
+ down_read(&zram->init_lock);
+ val = atomic64_read(&zram->stats.bd_wb_limit);
+ up_read(&zram->init_lock);
+
+ return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
+}
+
static void reset_bdev(struct zram *zram)
{
struct block_device *bdev;
@@ -612,6 +645,11 @@ static ssize_t writeback_store(struct device *dev,
bvec.bv_len = PAGE_SIZE;
bvec.bv_offset = 0;
+ if (zram->stop_writeback) {
+ ret = -EIO;
+ break;
+ }
+
if (!blk_idx) {
blk_idx = alloc_block_bdev(zram);
if (!blk_idx) {
@@ -694,6 +732,11 @@ 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;
+ }
next:
zram_slot_unlock(zram, index);
}
@@ -1018,6 +1061,7 @@ static ssize_t mm_stat_show(struct device *dev,
}
#ifdef CONFIG_ZRAM_WRITEBACK
+#define FOUR_K(x) ((x) * (1 << (PAGE_SHIFT - 12)))
static ssize_t bd_stat_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -1027,9 +1071,9 @@ static ssize_t bd_stat_show(struct device *dev,
down_read(&zram->init_lock);
ret = scnprintf(buf, PAGE_SIZE,
"%8llu %8llu %8llu\n",
- (u64)atomic64_read(&zram->stats.bd_count) * (PAGE_SHIFT - 12),
- (u64)atomic64_read(&zram->stats.bd_reads) * (PAGE_SHIFT - 12),
- (u64)atomic64_read(&zram->stats.bd_writes) * (PAGE_SHIFT - 12));
+ FOUR_K((u64)atomic64_read(&zram->stats.bd_count)),
+ FOUR_K((u64)atomic64_read(&zram->stats.bd_reads)),
+ FOUR_K((u64)atomic64_read(&zram->stats.bd_writes)));
up_read(&zram->init_lock);
return ret;
@@ -1767,6 +1811,7 @@ static DEVICE_ATTR_RW(comp_algorithm);
#ifdef CONFIG_ZRAM_WRITEBACK
static DEVICE_ATTR_RW(backing_dev);
static DEVICE_ATTR_WO(writeback);
+static DEVICE_ATTR_RW(writeback_limit);
#endif
static struct attribute *zram_disk_attrs[] = {
@@ -1782,6 +1827,7 @@ static struct attribute *zram_disk_attrs[] = {
#ifdef CONFIG_ZRAM_WRITEBACK
&dev_attr_backing_dev.attr,
&dev_attr_writeback.attr,
+ &dev_attr_writeback_limit.attr,
#endif
&dev_attr_io_stat.attr,
&dev_attr_mm_stat.attr,
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index bc477803530d..4bd3afd15e83 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -86,6 +86,7 @@ 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
};
@@ -113,6 +114,7 @@ struct zram {
*/
bool claim; /* Protected by bdev->bd_mutex */
struct file *backing_dev;
+ bool stop_writeback;
#ifdef CONFIG_ZRAM_WRITEBACK
struct block_device *bdev;
unsigned int old_block_size;