Commit 3923d485 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm writecache: implement gradual cleanup 



If a block is stored in the cache for too long, it will now be
written to the underlying device and cleaned up.

Add a new option "max_age" that specifies the maximum age of a block
in milliseconds.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 93de44eb

drivers/md/dm-writecache.c

+36 −1
Original line number Diff line number Diff line
@@ -26,6 +26,8 @@ 
#define AUTOCOMMIT_BLOCKS_SSD		65536

#define AUTOCOMMIT_BLOCKS_PMEM		64

#define AUTOCOMMIT_MSEC			1000

#define MAX_AGE_DIV			16

#define MAX_AGE_UNSPECIFIED		-1UL



#define BITMAP_GRANULARITY	65536

#if BITMAP_GRANULARITY < PAGE_SIZE
@@ -88,6 +90,7 @@ struct wc_entry { 
		:47

#endif

	;

	unsigned long age;

#ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS

	uint64_t original_sector;

	uint64_t seq_count;
@@ -119,6 +122,7 @@ struct dm_writecache { 
	size_t writeback_size;

	size_t freelist_high_watermark;

	size_t freelist_low_watermark;

	unsigned long max_age;



	unsigned uncommitted_blocks;

	unsigned autocommit_blocks;
@@ -130,6 +134,8 @@ struct dm_writecache { 
	struct timer_list autocommit_timer;

	struct wait_queue_head freelist_wait;



	struct timer_list max_age_timer;



	atomic_t bio_in_progress[2];

	struct wait_queue_head bio_in_progress_wait[2];
@@ -597,6 +603,7 @@ static void writecache_insert_entry(struct dm_writecache *wc, struct wc_entry *i 
	rb_link_node(&ins->rb_node, parent, node);

	rb_insert_color(&ins->rb_node, &wc->tree);

	list_add(&ins->lru, &wc->lru);

	ins->age = jiffies;

}



static void writecache_unlink(struct dm_writecache *wc, struct wc_entry *e)
@@ -632,6 +639,16 @@ static inline void writecache_verify_watermark(struct dm_writecache *wc) 
		queue_work(wc->writeback_wq, &wc->writeback_work);

}



static void writecache_max_age_timer(struct timer_list *t)

{

	struct dm_writecache *wc = from_timer(wc, t, max_age_timer);



	if (!dm_suspended(wc->ti) && !writecache_has_error(wc)) {

		queue_work(wc->writeback_wq, &wc->writeback_work);

		mod_timer(&wc->max_age_timer, jiffies + wc->max_age / MAX_AGE_DIV);

	}

}



static struct wc_entry *writecache_pop_from_freelist(struct dm_writecache *wc, sector_t expected_sector)

{

	struct wc_entry *e;
@@ -838,6 +855,7 @@ static void writecache_suspend(struct dm_target *ti) 
	bool flush_on_suspend;



	del_timer_sync(&wc->autocommit_timer);

	del_timer_sync(&wc->max_age_timer);



	wc_lock(wc);

	writecache_flush(wc);
@@ -974,6 +992,9 @@ erase_this: 


	writecache_verify_watermark(wc);



	if (wc->max_age != MAX_AGE_UNSPECIFIED)

		mod_timer(&wc->max_age_timer, jiffies + wc->max_age / MAX_AGE_DIV);



	wc_unlock(wc);

}
@@ -1661,7 +1682,9 @@ restart: 
	wbl.size = 0;

	while (!list_empty(&wc->lru) &&

	       (wc->writeback_all ||

		wc->freelist_size + wc->writeback_size <= wc->freelist_low_watermark)) {

		wc->freelist_size + wc->writeback_size <= wc->freelist_low_watermark ||

		(jiffies - container_of(wc->lru.prev, struct wc_entry, lru)->age >=

		 wc->max_age - wc->max_age / MAX_AGE_DIV))) {



		n_walked++;

		if (unlikely(n_walked > WRITEBACK_LATENCY) &&
@@ -1924,9 +1947,11 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv) 
	wc->ti = ti;



	mutex_init(&wc->lock);

	wc->max_age = MAX_AGE_UNSPECIFIED;

	writecache_poison_lists(wc);

	init_waitqueue_head(&wc->freelist_wait);

	timer_setup(&wc->autocommit_timer, writecache_autocommit_timer, 0);

	timer_setup(&wc->max_age_timer, writecache_max_age_timer, 0);



	for (i = 0; i < 2; i++) {

		atomic_set(&wc->bio_in_progress[i], 0);
@@ -2100,6 +2125,14 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv) 
				goto invalid_optional;

			wc->autocommit_jiffies = msecs_to_jiffies(autocommit_msecs);

			wc->autocommit_time_set = true;

		} else if (!strcasecmp(string, "max_age") && opt_params >= 1) {

			unsigned max_age_msecs;

			string = dm_shift_arg(&as), opt_params--;

			if (sscanf(string, "%u%c", &max_age_msecs, &dummy) != 1)

				goto invalid_optional;

			if (max_age_msecs > 86400000)

				goto invalid_optional;

			wc->max_age = msecs_to_jiffies(max_age_msecs);

		} else if (!strcasecmp(string, "cleaner")) {

			wc->cleaner = true;

		} else if (!strcasecmp(string, "fua")) {
@@ -2361,6 +2394,8 @@ static void writecache_status(struct dm_target *ti, status_type_t type, 
			DMEMIT(" autocommit_blocks %u", wc->autocommit_blocks);

		if (wc->autocommit_time_set)

			DMEMIT(" autocommit_time %u", jiffies_to_msecs(wc->autocommit_jiffies));

		if (wc->max_age != MAX_AGE_UNSPECIFIED)

			DMEMIT(" max_age %u", jiffies_to_msecs(wc->max_age));

		if (wc->cleaner)

			DMEMIT(" cleaner");

		if (wc->writeback_fua_set)

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