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: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 3f17dcc..e5c7b90 100644 (file)
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -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)