ceph: maintain i_head_snapc when any caps are dirty, not just for data
We used to use i_head_snapc to keep track of which snapc the current epoch
of dirty data was dirtied under. It is used by queue_cap_snap to set up
the cap_snap. However, since we queue cap snaps for any dirty caps, not
just for dirty file data, we need to keep a valid i_head_snapc anytime
we have dirty|flushing caps. This fixes a NULL pointer deref in
queue_cap_snap when writing back dirty caps without data (e.g.,
snaptest-authwb.sh).
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index b33929d8..c33897a 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -344,7 +344,8 @@
unsigned i_cap_exporting_issued;
struct ceph_cap_reservation i_cap_migration_resv;
struct list_head i_cap_snaps; /* snapped state pending flush to mds */
- struct ceph_snap_context *i_head_snapc; /* set if wr_buffer_head > 0 */
+ struct ceph_snap_context *i_head_snapc; /* set if wr_buffer_head > 0 or
+ dirty|flushing caps */
unsigned i_snap_caps; /* cap bits for snapped files */
int i_nr_by_mode[CEPH_FILE_MODE_NUM]; /* open file counts */