From: Minchan Kim <minchan@xxxxxxxxxx> Subject: zram: support page writeback There is demand to writeback specific process pages to backing store instead of all idles pages in the system due to storage wear out concerns and to launching latency of apps which are most of the time idle but are critical for resume latency. This patch extends the writeback knob to support a specific page writeback. Link: https://lkml.kernel.org/r/20201020190506.3758660-1-minchan@xxxxxxxxxx Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/blockdev/zram.rst | 5 ++++ drivers/block/zram/zram_drv.c | 21 ++++++++++++++---- 2 files changed, 22 insertions(+), 4 deletions(-) --- a/Documentation/admin-guide/blockdev/zram.rst~zram-support-a-page-writeback +++ a/Documentation/admin-guide/blockdev/zram.rst @@ -334,6 +334,11 @@ Admin can request writeback of those idl With the command, zram writeback idle pages from memory to the storage. +If admin want to write a specific page in zram device to backing device, +they could write a page index into the interface. + + echo "page_index=1251" > /sys/block/zramX/writeback + 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. --- a/drivers/block/zram/zram_drv.c~zram-support-a-page-writeback +++ a/drivers/block/zram/zram_drv.c @@ -620,15 +620,19 @@ static int read_from_bdev_async(struct z return 1; } +#define PAGE_WB_SIG "page_index=" + +#define PAGE_WRITEBACK 0 #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) { struct zram *zram = dev_to_zram(dev); unsigned long nr_pages = zram->disksize >> PAGE_SHIFT; - unsigned long index; + unsigned long index = 0; struct bio bio; struct bio_vec bio_vec; struct page *page; @@ -640,8 +644,17 @@ static ssize_t writeback_store(struct de mode = IDLE_WRITEBACK; else if (sysfs_streq(buf, "huge")) mode = HUGE_WRITEBACK; - else - return -EINVAL; + else { + if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1)) + return -EINVAL; + + ret = kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index); + if (ret || index >= nr_pages) + return -EINVAL; + + nr_pages = 1; + mode = PAGE_WRITEBACK; + } down_read(&zram->init_lock); if (!init_done(zram)) { @@ -660,7 +673,7 @@ static ssize_t writeback_store(struct de goto release_init_lock; } - for (index = 0; index < nr_pages; index++) { + while (nr_pages--) { struct bio_vec bvec; bvec.bv_page = page; _
