mainline inclusion from mainline-5.3-rc1 commit 2464b693148e5d5ca42b6064bb40c1a275ea61cd category: backport
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@suse.de Signed-off-by: Jens Axboe axboe@kernel.dk --- 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 33556acdcf9c..749de7a56fef 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;