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/addr.c b/fs/ceph/addr.c
index 420d469..4cfce1e 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -87,7 +87,7 @@
/* dirty the head */
spin_lock(&inode->i_lock);
- if (ci->i_wrbuffer_ref_head == 0)
+ if (ci->i_head_snapc == NULL)
ci->i_head_snapc = ceph_get_snap_context(snapc);
++ci->i_wrbuffer_ref_head;
if (ci->i_wrbuffer_ref == 0)
@@ -346,7 +346,7 @@
break;
}
}
- if (!snapc && ci->i_head_snapc) {
+ if (!snapc && ci->i_wrbuffer_ref_head) {
snapc = ceph_get_snap_context(ci->i_head_snapc);
dout(" head snapc %p has %d dirty pages\n",
snapc, ci->i_wrbuffer_ref_head);