This patch adds more code comments in journal_read_bucket(), this is an
effort to make the code to be more understandable.
Signed-off-by: Coly Li <colyli@xxxxxxx>
---
drivers/md/bcache/journal.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index f18c1e7b012c..50c9a1e405e6 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -100,6 +100,20 @@ reread: left = ca->sb.bucket_size - offset;
blocks = set_blocks(j, block_bytes(ca->set));
+ /*
+ * Nodes in 'list' are in linear increasing order of
+ * i->j.seq, the node on head has the smallest (oldest)
+ * journal seq, the node on tail has the biggest
+ * (latest) journal seq.
+ */
+
+ /*
+ * Check from the oldest jset for last_seq. If
+ * i->j.seq < j->last_seq, it means the oldest jset
+ * in list is expired and useless, remove it from
+ * this list. Otherwise, j is a condidate jset for
+ * further following checks.
+ */
while (!list_empty(list)) {
i = list_first_entry(list,
struct journal_replay, list);
@@ -109,13 +123,22 @@ reread: left = ca->sb.bucket_size - offset;
kfree(i);
}
+ /* iterate list in reverse order (from latest jset) */
list_for_each_entry_reverse(i, list, list) {
if (j->seq == i->j.seq)
goto next_set;
+ /*
+ * if j->seq is less than any i->j.last_seq
+ * in list, j is an expired and useless jset.
+ */
if (j->seq < i->j.last_seq)
goto next_set;
+ /*
+ * 'where' points to first jset in list which
+ * is elder then j.
+ */
if (j->seq > i->j.seq) {
where = &i->list;
goto add;
@@ -129,6 +152,7 @@ reread: left = ca->sb.bucket_size - offset;
if (!i)
return -ENOMEM;
memcpy(&i->j, j, bytes);
+ /* Add to the location after 'where' points to */
list_add(&i->list, where);
ret = 1;
--
2.16.4
