bcache: Fix for when no journal entries are found

The journal replay code didn't handle this case, causing it to go into
an infinite loop...

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: linux-stable <stable@vger.kernel.org> # >= v3.10
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 12 deletions

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index c0017ca32b76..f5203dfc4cfe 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -153,7 +153,8 @@ int bch_journal_read(struct cache_set *c, struct list_head *list,
                 bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
                 pr_debug("%u journal buckets", ca->sb.njournal_buckets);
 
-                /* Read journal buckets ordered by golden ratio hash to quickly
+                /*
+                 * Read journal buckets ordered by golden ratio hash to quickly
                  * find a sequence of buckets with valid journal entries
                  */
                 for (i = 0; i < ca->sb.njournal_buckets; i++) {
@@ -166,18 +167,20 @@ int bch_journal_read(struct cache_set *c, struct list_head *list,
                                 goto bsearch;
                 }
 
-                /* If that fails, check all the buckets we haven't checked
+                /*
+                 * If that fails, check all the buckets we haven't checked
                  * already
                  */
                 pr_debug("falling back to linear search");
 
-                for (l = 0; l < ca->sb.njournal_buckets; l++) {
-                        if (test_bit(l, bitmap))
-                                continue;
-
+                for (l = find_first_zero_bit(bitmap, ca->sb.njournal_buckets);
+                     l < ca->sb.njournal_buckets;
+                     l = find_next_zero_bit(bitmap, ca->sb.njournal_buckets, l + 1))
                         if (read_bucket(l))
                                 goto bsearch;
-                }
+
+                if (list_empty(list))
+                        continue;
 bsearch:
                 /* Binary search */
                 m = r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
@@ -197,10 +200,12 @@ bsearch:
                                 r = m;
                 }
 
-                /* Read buckets in reverse order until we stop finding more
+                /*
+                 * Read buckets in reverse order until we stop finding more
                  * journal entries
                  */
-                pr_debug("finishing up");
+                pr_debug("finishing up: m %u njournal_buckets %u",
+                         m, ca->sb.njournal_buckets);
                 l = m;
 
                 while (1) {
@@ -228,9 +233,10 @@ bsearch:
                         }
         }
 
-        c->journal.seq = list_entry(list->prev,
-                                    struct journal_replay,
-                                    list)->j.seq;
+        if (!list_empty(list))
+                c->journal.seq = list_entry(list->prev,
+                                            struct journal_replay,
+                                            list)->j.seq;
 
         return 0;
 #undef read_bucket