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/snap.c b/fs/ceph/snap.c
index 6bdbf3a..4868b9d 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -458,6 +458,8 @@
CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_WR))) {
struct ceph_snap_context *snapc = ci->i_head_snapc;
+ dout("queue_cap_snap %p cap_snap %p queuing under %p\n", inode,
+ capsnap, snapc);
igrab(inode);
atomic_set(&capsnap->nref, 1);
@@ -489,7 +491,9 @@
capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
ci->i_wrbuffer_ref_head = 0;
capsnap->context = snapc;
- ci->i_head_snapc = NULL;
+ ci->i_head_snapc =
+ ceph_get_snap_context(ci->i_snap_realm->cached_context);
+ dout(" new snapc is %p\n", ci->i_head_snapc);
list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
if (used & CEPH_CAP_FILE_WR) {