bcache: Journal replay fix

The journal replay code starts by finding something that looks like a
valid journal entry, then it does a binary search over the unchecked
region of the journal for the journal entries with the highest sequence
numbers.

Trouble is, the logic was wrong - journal_read_bucket() returns true if
it found journal entries we need, but if the range of journal entries
we're looking for loops around the end of the journal - in that case
journal_read_bucket() could return true when it hadn't found the highest
sequence number we'd seen yet, and in that case the binary search did
the wrong thing. Whoops.

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

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 4b250667bb7f..ba95ab84b2be 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -184,9 +184,14 @@ bsearch:
                 pr_debug("starting binary search, l %u r %u", l, r);
 
                 while (l + 1 < r) {
+                        seq = list_entry(list->prev, struct journal_replay,
+                                         list)->j.seq;
+
                         m = (l + r) >> 1;
+                        read_bucket(m);
 
-                        if (read_bucket(m))
+                        if (seq != list_entry(list->prev, struct journal_replay,
+                                              list)->j.seq)
                                 l = m;
                         else
                                 r = m;