The patch titled
Subject: zram: add incompressible writeback
has been added to the -mm mm-unstable branch. Its filename is
zram-add-incompressible-writeback.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-add-incompressible-writeback.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Subject: zram: add incompressible writeback
Date: Wed, 9 Nov 2022 20:50:46 +0900
Add support for incompressible pages writeback:
echo incompressible > /sys/block/zramX/writeback
Link: https://lkml.kernel.org/r/20221109115047.2921851-13-senozhatsky@xxxxxxxxxxxx
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Alexey Romanov <avromanov@xxxxxxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Cc: Suleiman Souhlal <suleiman@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/blockdev/zram.rst | 7 ++++++-
drivers/block/zram/zram_drv.c | 18 ++++++++++++------
2 files changed, 18 insertions(+), 7 deletions(-)
--- a/Documentation/admin-guide/blockdev/zram.rst~zram-add-incompressible-writeback
+++ a/Documentation/admin-guide/blockdev/zram.rst
@@ -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
--- a/drivers/block/zram/zram_drv.c~zram-add-incompressible-writeback
+++ a/drivers/block/zram/zram_drv.c
@@ -645,10 +645,10 @@ static int read_from_bdev_async(struct z
#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)
@@ -669,6 +669,8 @@ static ssize_t writeback_store(struct de
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;
@@ -731,11 +733,15 @@ static ssize_t writeback_store(struct de
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.
_
Patches currently in -mm which might be from senozhatsky@xxxxxxxxxxxx are
zram-preparation-for-multi-zcomp-support.patch
zram-add-recompression-algorithm-sysfs-knob.patch
zram-factor-out-wb-and-non-wb-zram-read-functions.patch
zram-introduce-recompress-sysfs-knob.patch
zram-add-recompress-flag-to-read_block_state.patch
zram-clarify-writeback_store-comment.patch
zram-use-is_err_value-to-check-for-zs_malloc-errors.patch
zram-remove-redundant-checks-from-zram_recompress.patch
zram-add-algo-parameter-support-to-zram_recompress.patch
documentation-add-zram-recompression-documentation.patch
zram-add-incompressible-writeback.patch
zram-add-incompressible-flag-to-read_block_state.patch
