Commit b46f9ea3 authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Andrew Morton
Browse files

zram: add incompressible writeback 

Add support for incompressible pages writeback:

  echo incompressible > /sys/block/zramX/writeback

Link: https://lkml.kernel.org/r/20221109115047.2921851-13-senozhatsky@chromium.org


Signed-off-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 443dd798

Documentation/admin-guide/blockdev/zram.rst

+6 −1
Original line number Diff line number Diff line
@@ -348,8 +348,13 @@ this can be accomplished with:: 


        echo huge_idle > /sys/block/zramX/writeback



If a user chooses to writeback only incompressible pages (pages that none of

algorithms can compress) this can be accomplished with::



	echo incompressible > /sys/block/zramX/writeback



If an admin wants to write a specific page in zram device to the backing device,

they could write a page index into the interface.

they could write a page index into the interface::



	echo "page_index=1251" > /sys/block/zramX/writeback

drivers/block/zram/zram_drv.c

+12 −6
Original line number Diff line number Diff line
@@ -648,7 +648,7 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec, 
#define PAGE_WRITEBACK			0

#define HUGE_WRITEBACK			(1<<0)

#define IDLE_WRITEBACK			(1<<1)



#define INCOMPRESSIBLE_WRITEBACK	(1<<2)



static ssize_t writeback_store(struct device *dev,

		struct device_attribute *attr, const char *buf, size_t len)
@@ -669,6 +669,8 @@ static ssize_t writeback_store(struct device *dev, 
		mode = HUGE_WRITEBACK;

	else if (sysfs_streq(buf, "huge_idle"))

		mode = IDLE_WRITEBACK | HUGE_WRITEBACK;

	else if (sysfs_streq(buf, "incompressible"))

		mode = INCOMPRESSIBLE_WRITEBACK;

	else {

		if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1))

			return -EINVAL;
@@ -736,6 +738,10 @@ static ssize_t writeback_store(struct device *dev, 
		if (mode & HUGE_WRITEBACK &&

		    !zram_test_flag(zram, index, ZRAM_HUGE))

			goto next;

		if (mode & INCOMPRESSIBLE_WRITEBACK &&

		    !zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))

			goto next;



		/*

		 * Clearing ZRAM_UNDER_WB is duty of caller.

		 * IOW, zram_free_page never clear it.