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/caps.c b/fs/ceph/caps.c
index ba5bbf3..a2069b6 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1143,6 +1143,10 @@
for (i = 0; i < CEPH_CAP_BITS; i++)
if (flushing & (1 << i))
ci->i_cap_flush_tid[i] = flush_tid;
+
+ follows = ci->i_head_snapc->seq;
+ } else {
+ follows = 0;
}
keep = cap->implemented;
@@ -1156,7 +1160,6 @@
mtime = inode->i_mtime;
atime = inode->i_atime;
time_warp_seq = ci->i_time_warp_seq;
- follows = ci->i_snap_realm->cached_context->seq;
uid = inode->i_uid;
gid = inode->i_gid;
mode = inode->i_mode;
@@ -1332,7 +1335,11 @@
ceph_cap_string(was | mask));
ci->i_dirty_caps |= mask;
if (was == 0) {
- dout(" inode %p now dirty\n", &ci->vfs_inode);
+ if (!ci->i_head_snapc)
+ ci->i_head_snapc = ceph_get_snap_context(
+ ci->i_snap_realm->cached_context);
+ dout(" inode %p now dirty snapc %p\n", &ci->vfs_inode,
+ ci->i_head_snapc);
BUG_ON(!list_empty(&ci->i_dirty_item));
spin_lock(&mdsc->cap_dirty_lock);
list_add(&ci->i_dirty_item, &mdsc->cap_dirty);
@@ -2190,7 +2197,9 @@
if (ci->i_head_snapc == snapc) {
ci->i_wrbuffer_ref_head -= nr;
- if (!ci->i_wrbuffer_ref_head) {
+ if (ci->i_wrbuffer_ref_head == 0 &&
+ ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) {
+ BUG_ON(!ci->i_head_snapc);
ceph_put_snap_context(ci->i_head_snapc);
ci->i_head_snapc = NULL;
}
@@ -2483,6 +2492,11 @@
dout(" inode %p now clean\n", inode);
BUG_ON(!list_empty(&ci->i_dirty_item));
drop = 1;
+ if (ci->i_wrbuffer_ref_head == 0) {
+ BUG_ON(!ci->i_head_snapc);
+ ceph_put_snap_context(ci->i_head_snapc);
+ ci->i_head_snapc = NULL;
+ }
} else {
BUG_ON(list_empty(&ci->i_dirty_item));
}