Commit 657a81fe authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Andrew Morton
Browse files

zram: drop pp_in_progress 

pp_in_progress makes sure that only one post-processing (writeback or
recomrpession) is active at any given time.  Functionality wise it,
basically, shadows zram init_lock, when init_lock is acquired in writer
mode.

Switch recompress_store() and writeback_store() to take zram init_lock in
writer mode, like all store() sysfs handlers should do, so that we can
drop pp_in_progress.  Recompression and writeback can be somewhat slow, so
holding init_lock in writer mode can block zram attrs reads, but in
reality the only zram attrs reads that take place are mm_stat reads, and
usually it's the same process that reads mm_stat and does recompression or
writeback.

Link: https://lkml.kernel.org/r/20251216071342.687993-1-senozhatsky@chromium.org


Signed-off-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Suggested-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 9082f24b

drivers/block/zram/zram_drv.c

+8 −24
Original line number Diff line number Diff line
@@ -902,7 +902,7 @@ static struct zram_wb_ctl *init_wb_ctl(struct zram *zram) 


static void zram_account_writeback_rollback(struct zram *zram)

{

	lockdep_assert_held_read(&zram->init_lock);

	lockdep_assert_held_write(&zram->init_lock);



	if (zram->wb_limit_enable)

		zram->bd_wb_limit +=  1UL << (PAGE_SHIFT - 12);
@@ -910,7 +910,7 @@ static void zram_account_writeback_rollback(struct zram *zram) 


static void zram_account_writeback_submit(struct zram *zram)

{

	lockdep_assert_held_read(&zram->init_lock);

	lockdep_assert_held_write(&zram->init_lock);



	if (zram->wb_limit_enable && zram->bd_wb_limit > 0)

		zram->bd_wb_limit -=  1UL << (PAGE_SHIFT - 12);
@@ -1264,24 +1264,16 @@ static ssize_t writeback_store(struct device *dev, 
	ssize_t ret = len;

	int err, mode = 0;



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

	guard(rwsem_write)(&zram->init_lock);

	if (!init_done(zram))

		return -EINVAL;



	/* Do not permit concurrent post-processing actions. */

	if (atomic_xchg(&zram->pp_in_progress, 1))

		return -EAGAIN;



	if (!zram->backing_dev) {

		ret = -ENODEV;

		goto out;

	}

	if (!zram->backing_dev)

		return -ENODEV;



	pp_ctl = init_pp_ctl();

	if (!pp_ctl) {

		ret = -ENOMEM;

		goto out;

	}

	if (!pp_ctl)

		return -ENOMEM;



	wb_ctl = init_wb_ctl(zram);

	if (!wb_ctl) {
@@ -1358,7 +1350,6 @@ static ssize_t writeback_store(struct device *dev, 
out:

	release_pp_ctl(zram, pp_ctl);

	release_wb_ctl(wb_ctl);

	atomic_set(&zram->pp_in_progress, 0);



	return ret;

}
@@ -2619,14 +2610,10 @@ static ssize_t recompress_store(struct device *dev, 
	if (threshold >= huge_class_size)

		return -EINVAL;



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

	guard(rwsem_write)(&zram->init_lock);

	if (!init_done(zram))

		return -EINVAL;



	/* Do not permit concurrent post-processing actions. */

	if (atomic_xchg(&zram->pp_in_progress, 1))

		return -EAGAIN;



	if (algo) {

		bool found = false;
@@ -2697,7 +2684,6 @@ static ssize_t recompress_store(struct device *dev, 
	if (page)

		__free_page(page);

	release_pp_ctl(zram, ctl);

	atomic_set(&zram->pp_in_progress, 0);

	return ret;

}

#endif
@@ -2888,7 +2874,6 @@ static void zram_reset_device(struct zram *zram) 
	zram->disksize = 0;

	zram_destroy_comps(zram);

	memset(&zram->stats, 0, sizeof(zram->stats));

	atomic_set(&zram->pp_in_progress, 0);

	reset_bdev(zram);



	comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
@@ -3124,7 +3109,6 @@ static int zram_add(void) 
	zram->disk->fops = &zram_devops;

	zram->disk->private_data = zram;

	snprintf(zram->disk->disk_name, 16, "zram%d", device_id);

	atomic_set(&zram->pp_in_progress, 0);

	zram_comp_params_reset(zram);

	comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);

drivers/block/zram/zram_drv.h

+0 −1
Original line number Diff line number Diff line
@@ -143,6 +143,5 @@ struct zram { 
#ifdef CONFIG_ZRAM_MEMORY_TRACKING

	struct dentry *debugfs_dir;

#endif

	atomic_t pp_in_progress;

};

#endif