@@ -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
@@ -648,10 +648,10 @@ static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
#define PAGE_WB_SIG "page_index="
-#define PAGE_WRITEBACK 0
-#define HUGE_WRITEBACK (1<<0)
-#define IDLE_WRITEBACK (1<<1)
-
+#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)
@@ -672,6 +672,8 @@ 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;
@@ -734,11 +736,15 @@ static ssize_t writeback_store(struct device *dev,
goto next;
if (mode & IDLE_WRITEBACK &&
- !zram_test_flag(zram, index, ZRAM_IDLE))
+ !zram_test_flag(zram, index, ZRAM_IDLE))
goto next;
if (mode & HUGE_WRITEBACK &&
- !zram_test_flag(zram, index, ZRAM_HUGE))
+ !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.
Add support for incompressible pages writeback: echo incompressible > /sys/block/zramX/writeback Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> --- Documentation/admin-guide/blockdev/zram.rst | 7 ++++++- drivers/block/zram/zram_drv.c | 18 ++++++++++++------ 2 files changed, 18 insertions(+), 7 deletions(-)