This patch implements gradual cleanup for dm-writecache - if the block is
stored in the cache for too long, it will be written to the underlying
device and cleaned up.
The patch adds a new option "max_age" that specified the maximum age of a
block in milliseconds.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/md/dm-writecache.c | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 insertions(+), 1 deletion(-)
Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c 2020-02-23 18:16:22.000000000 +0100
+++ linux-2.6/drivers/md/dm-writecache.c 2020-02-23 18:16:22.000000000 +0100
@@ -26,6 +26,7 @@
#define AUTOCOMMIT_BLOCKS_SSD 65536
#define AUTOCOMMIT_BLOCKS_PMEM 64
#define AUTOCOMMIT_MSEC 1000
+#define MAX_AGE_DIV 16
#define BITMAP_GRANULARITY 65536
#if BITMAP_GRANULARITY < PAGE_SIZE
@@ -88,6 +89,7 @@ struct wc_entry {
:47
#endif
;
+ unsigned long age;
#ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
uint64_t original_sector;
uint64_t seq_count;
@@ -119,6 +121,7 @@ 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 +133,8 @@ 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 +602,7 @@ static void writecache_insert_entry(stru
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 +638,15 @@ static inline void writecache_verify_wat
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 +853,7 @@ static void writecache_suspend(struct dm
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 +990,9 @@ erase_this:
writecache_verify_watermark(wc);
+ if (wc->max_age != -1UL)
+ mod_timer(&wc->max_age_timer, jiffies + wc->max_age / MAX_AGE_DIV);
+
wc_unlock(wc);
}
@@ -1661,7 +1680,8 @@ 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 +1944,11 @@ static int writecache_ctr(struct dm_targ
wc->ti = ti;
mutex_init(&wc->lock);
+ wc->max_age = -1UL;
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 +2122,14 @@ static int writecache_ctr(struct dm_targ
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 +2391,8 @@ static void writecache_status(struct dm_
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 != -1UL)
+ DMEMIT(" max_age %u", jiffies_to_msecs(wc->max_age));
if (wc->cleaner)
DMEMIT(" cleaner");
if (wc->writeback_fua_set)
--
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