Commit ba4c3698 authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Andrew Morton
Browse files

zram: rename writeback_compressed device attr 

Rename writeback_compressed attr to compressed_writeback to avoid possible
confusion and have more natural naming.  writeback_compressed may look
like an alternative version of writeback while in fact
writeback_compressed only sets a writeback property.  Make this
distinction more clear with a new compressed_writeback name.

This updates a feature which is new in 7.0-rcX.

Link: https://lkml.kernel.org/r/20260226025429.1042083-1-senozhatsky@chromium.org


Fixes: 4c1d6138 ("zram: introduce writeback_compressed device attribute")
Signed-off-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Suggested-by: default avatarMinchan Kim <minchan@kernel.org>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Christoph Böhmwalder" <christoph.boehmwalder@linbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 5548dd7f

Documentation/ABI/testing/sysfs-block-zram

+2 −2
Original line number Diff line number Diff line
@@ -151,11 +151,11 @@ Description: 
		The algorithm_params file is write-only and is used to setup

		compression algorithm parameters.



What:		/sys/block/zram<id>/writeback_compressed

What:		/sys/block/zram<id>/compressed_writeback

Date:		Decemeber 2025

Contact:	Richard Chang <richardycc@google.com>

Description:

		The writeback_compressed device atrribute toggles compressed

		The compressed_writeback device atrribute toggles compressed

		writeback feature.



What:		/sys/block/zram<id>/writeback_batch_size

Documentation/admin-guide/blockdev/zram.rst

+3 −3
Original line number Diff line number Diff line
@@ -216,7 +216,7 @@ writeback_limit WO specifies the maximum amount of write IO zram 
writeback_limit_enable  RW	show and set writeback_limit feature

writeback_batch_size	RW	show and set maximum number of in-flight

				writeback operations

writeback_compressed	RW	show and set compressed writeback feature

compressed_writeback	RW	show and set compressed writeback feature

comp_algorithm    	RW	show and change the compression algorithm

algorithm_params	WO	setup compression algorithm parameters

compact           	WO	trigger memory compaction
@@ -439,11 +439,11 @@ budget in next setting is user's job. 
By default zram stores written back pages in decompressed (raw) form, which

means that writeback operation involves decompression of the page before

writing it to the backing device.  This behavior can be changed by enabling

`writeback_compressed` feature, which causes zram to write compressed pages

`compressed_writeback` feature, which causes zram to write compressed pages

to the backing device, thus avoiding decompression overhead.  To enable

this feature, execute::



	$ echo yes > /sys/block/zramX/writeback_compressed

	$ echo yes > /sys/block/zramX/compressed_writeback



Note that this feature should be configured before the `zramX` device is

initialized.

drivers/block/zram/zram_drv.c

+12 −12
Original line number Diff line number Diff line
@@ -549,7 +549,7 @@ static ssize_t bd_stat_show(struct device *dev, struct device_attribute *attr, 
	return ret;

}



static ssize_t writeback_compressed_store(struct device *dev,

static ssize_t compressed_writeback_store(struct device *dev,

					  struct device_attribute *attr,

					  const char *buf, size_t len)

{
@@ -564,12 +564,12 @@ static ssize_t writeback_compressed_store(struct device *dev, 
		return -EBUSY;

	}



	zram->wb_compressed = val;

	zram->compressed_wb = val;



	return len;

}



static ssize_t writeback_compressed_show(struct device *dev,

static ssize_t compressed_writeback_show(struct device *dev,

					 struct device_attribute *attr,

					 char *buf)

{
@@ -577,7 +577,7 @@ static ssize_t writeback_compressed_show(struct device *dev, 
	struct zram *zram = dev_to_zram(dev);



	guard(rwsem_read)(&zram->dev_lock);

	val = zram->wb_compressed;

	val = zram->compressed_wb;



	return sysfs_emit(buf, "%d\n", val);

}
@@ -946,7 +946,7 @@ static int zram_writeback_complete(struct zram *zram, struct zram_wb_req *req) 
		goto out;

	}



	if (zram->wb_compressed) {

	if (zram->compressed_wb) {

		/*

		 * ZRAM_WB slots get freed, we need to preserve data required

		 * for read decompression.
@@ -960,7 +960,7 @@ static int zram_writeback_complete(struct zram *zram, struct zram_wb_req *req) 
	set_slot_flag(zram, index, ZRAM_WB);

	set_slot_handle(zram, index, req->blk_idx);



	if (zram->wb_compressed) {

	if (zram->compressed_wb) {

		if (huge)

			set_slot_flag(zram, index, ZRAM_HUGE);

		set_slot_size(zram, index, size);
@@ -1100,7 +1100,7 @@ static int zram_writeback_slots(struct zram *zram, 
		 */

		if (!test_slot_flag(zram, index, ZRAM_PP_SLOT))

			goto next;

		if (zram->wb_compressed)

		if (zram->compressed_wb)

			err = read_from_zspool_raw(zram, req->page, index);

		else

			err = read_from_zspool(zram, req->page, index);
@@ -1429,7 +1429,7 @@ static void zram_async_read_endio(struct bio *bio) 
	 *

	 * Keep the existing behavior for now.

	 */

	if (zram->wb_compressed == false) {

	if (zram->compressed_wb == false) {

		/* No decompression needed, complete the parent IO */

		bio_endio(req->parent);

		bio_put(bio);
@@ -1508,7 +1508,7 @@ static int read_from_bdev_sync(struct zram *zram, struct page *page, u32 index, 
	flush_work(&req.work);

	destroy_work_on_stack(&req.work);



	if (req.error || zram->wb_compressed == false)

	if (req.error || zram->compressed_wb == false)

		return req.error;



	return decompress_bdev_page(zram, page, index);
@@ -3007,7 +3007,7 @@ static DEVICE_ATTR_WO(writeback); 
static DEVICE_ATTR_RW(writeback_limit);

static DEVICE_ATTR_RW(writeback_limit_enable);

static DEVICE_ATTR_RW(writeback_batch_size);

static DEVICE_ATTR_RW(writeback_compressed);

static DEVICE_ATTR_RW(compressed_writeback);

#endif

#ifdef CONFIG_ZRAM_MULTI_COMP

static DEVICE_ATTR_RW(recomp_algorithm);
@@ -3031,7 +3031,7 @@ static struct attribute *zram_disk_attrs[] = { 
	&dev_attr_writeback_limit.attr,

	&dev_attr_writeback_limit_enable.attr,

	&dev_attr_writeback_batch_size.attr,

	&dev_attr_writeback_compressed.attr,

	&dev_attr_compressed_writeback.attr,

#endif

	&dev_attr_io_stat.attr,

	&dev_attr_mm_stat.attr,
@@ -3091,7 +3091,7 @@ static int zram_add(void) 
	init_rwsem(&zram->dev_lock);

#ifdef CONFIG_ZRAM_WRITEBACK

	zram->wb_batch_size = 32;

	zram->wb_compressed = false;

	zram->compressed_wb = false;

#endif



	/* gendisk structure */

drivers/block/zram/zram_drv.h

+1 −1
Original line number Diff line number Diff line
@@ -133,7 +133,7 @@ struct zram { 
#ifdef CONFIG_ZRAM_WRITEBACK

	struct file *backing_dev;

	bool wb_limit_enable;

	bool wb_compressed;

	bool compressed_wb;

	u32 wb_batch_size;

	u64 bd_wb_limit;

	struct block_device *bdev;