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path: root/drivers/md/bcache/journal.c
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Diffstat (limited to 'drivers/md/bcache/journal.c')
-rw-r--r--drivers/md/bcache/journal.c80
1 files changed, 75 insertions, 5 deletions
diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index be2a2a201603..33ddc5269e8d 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -417,10 +417,14 @@ err:
/* Journalling */
+#define nr_to_fifo_front(p, front_p, mask) (((p) - (front_p)) & (mask))
+
static void btree_flush_write(struct cache_set *c)
{
struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
- unsigned int i, n;
+ unsigned int i, nr, ref_nr;
+ atomic_t *fifo_front_p, *now_fifo_front_p;
+ size_t mask;
if (c->journal.btree_flushing)
return;
@@ -433,12 +437,50 @@ static void btree_flush_write(struct cache_set *c)
c->journal.btree_flushing = true;
spin_unlock(&c->journal.flush_write_lock);
+ /* get the oldest journal entry and check its refcount */
+ spin_lock(&c->journal.lock);
+ fifo_front_p = &fifo_front(&c->journal.pin);
+ ref_nr = atomic_read(fifo_front_p);
+ if (ref_nr <= 0) {
+ /*
+ * do nothing if no btree node references
+ * the oldest journal entry
+ */
+ spin_unlock(&c->journal.lock);
+ goto out;
+ }
+ spin_unlock(&c->journal.lock);
+
+ mask = c->journal.pin.mask;
+ nr = 0;
atomic_long_inc(&c->flush_write);
memset(btree_nodes, 0, sizeof(btree_nodes));
- n = 0;
mutex_lock(&c->bucket_lock);
list_for_each_entry_safe_reverse(b, t, &c->btree_cache, list) {
+ /*
+ * It is safe to get now_fifo_front_p without holding
+ * c->journal.lock here, because we don't need to know
+ * the exactly accurate value, just check whether the
+ * front pointer of c->journal.pin is changed.
+ */
+ now_fifo_front_p = &fifo_front(&c->journal.pin);
+ /*
+ * If the oldest journal entry is reclaimed and front
+ * pointer of c->journal.pin changes, it is unnecessary
+ * to scan c->btree_cache anymore, just quit the loop and
+ * flush out what we have already.
+ */
+ if (now_fifo_front_p != fifo_front_p)
+ break;
+ /*
+ * quit this loop if all matching btree nodes are
+ * scanned and record in btree_nodes[] already.
+ */
+ ref_nr = atomic_read(fifo_front_p);
+ if (nr >= ref_nr)
+ break;
+
if (btree_node_journal_flush(b))
pr_err("BUG: flush_write bit should not be set here!");
@@ -454,17 +496,44 @@ static void btree_flush_write(struct cache_set *c)
continue;
}
+ /*
+ * Only select the btree node which exactly references
+ * the oldest journal entry.
+ *
+ * If the journal entry pointed by fifo_front_p is
+ * reclaimed in parallel, don't worry:
+ * - the list_for_each_xxx loop will quit when checking
+ * next now_fifo_front_p.
+ * - If there are matched nodes recorded in btree_nodes[],
+ * they are clean now (this is why and how the oldest
+ * journal entry can be reclaimed). These selected nodes
+ * will be ignored and skipped in the folowing for-loop.
+ */
+ if (nr_to_fifo_front(btree_current_write(b)->journal,
+ fifo_front_p,
+ mask) != 0) {
+ mutex_unlock(&b->write_lock);
+ continue;
+ }
+
set_btree_node_journal_flush(b);
mutex_unlock(&b->write_lock);
- btree_nodes[n++] = b;
- if (n == BTREE_FLUSH_NR)
+ btree_nodes[nr++] = b;
+ /*
+ * To avoid holding c->bucket_lock too long time,
+ * only scan for BTREE_FLUSH_NR matched btree nodes
+ * at most. If there are more btree nodes reference
+ * the oldest journal entry, try to flush them next
+ * time when btree_flush_write() is called.
+ */
+ if (nr == BTREE_FLUSH_NR)
break;
}
mutex_unlock(&c->bucket_lock);
- for (i = 0; i < n; i++) {
+ for (i = 0; i < nr; i++) {
b = btree_nodes[i];
if (!b) {
pr_err("BUG: btree_nodes[%d] is NULL", i);
@@ -497,6 +566,7 @@ static void btree_flush_write(struct cache_set *c)
mutex_unlock(&b->write_lock);
}
+out:
spin_lock(&c->journal.flush_write_lock);
c->journal.btree_flushing = false;
spin_unlock(&c->journal.flush_write_lock);