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

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 4b250667bb7f5ed966d09890db69441203968828..ba95ab84b2be5a5a32292625d229bb29e051a53d 100644 (file)
--- 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;