ceph: queue_cap_snap should always queue dirty context

This simplifies the calling convention, and fixes a bug where we queue a
capsnap with a context other than i_head_snapc (the one that matches the
dirty pages).  The result was a BUG at fs/ceph/caps.c:2178 on writeback
completion when a capsnap matching the writeback snapc could not be found.

Signed-off-by: Sage Weil <sage@newdream.net>

2 files changed, 8 insertions, 11 deletions

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index 7e3e5f9edaa4..d197431532c0 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -430,8 +430,7 @@ static int dup_array(u64 **dst, __le64 *src, int num)
  * Caller must hold snap_rwsem for read (i.e., the realm topology won't
  * change).
  */
-void ceph_queue_cap_snap(struct ceph_inode_info *ci,
-                         struct ceph_snap_context *snapc)
+void ceph_queue_cap_snap(struct ceph_inode_info *ci)
 {
         struct inode *inode = &ci->vfs_inode;
         struct ceph_cap_snap *capsnap;
@@ -450,10 +449,11 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci,
                    as no new writes are allowed to start when pending, so any
                    writes in progress now were started before the previous
                    cap_snap.  lucky us. */
-                dout("queue_cap_snap %p snapc %p seq %llu used %d"
-                     " already pending\n", inode, snapc, snapc->seq, used);
+                dout("queue_cap_snap %p already pending\n", inode);
                 kfree(capsnap);
         } else if (ci->i_wrbuffer_ref_head || (used & CEPH_CAP_FILE_WR)) {
+                struct ceph_snap_context *snapc = ci->i_head_snapc;
+
                 igrab(inode);
 
                 atomic_set(&capsnap->nref, 1);
@@ -462,7 +462,6 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci,
                 INIT_LIST_HEAD(&capsnap->flushing_item);
 
                 capsnap->follows = snapc->seq - 1;
-                capsnap->context = ceph_get_snap_context(snapc);
                 capsnap->issued = __ceph_caps_issued(ci, NULL);
                 capsnap->dirty = __ceph_caps_dirty(ci);
 
@@ -479,7 +478,7 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci,
                    snapshot. */
                 capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
                 ci->i_wrbuffer_ref_head = 0;
-                ceph_put_snap_context(ci->i_head_snapc);
+                capsnap->context = snapc;
                 ci->i_head_snapc = NULL;
                 list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
 
@@ -603,7 +602,7 @@ more:
                                 if (lastinode)
                                         iput(lastinode);
                                 lastinode = inode;
-                                ceph_queue_cap_snap(ci, realm->cached_context);
+                                ceph_queue_cap_snap(ci);
                                 spin_lock(&realm->inodes_with_caps_lock);
                         }
                         spin_unlock(&realm->inodes_with_caps_lock);
@@ -825,8 +824,7 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
                         spin_unlock(&realm->inodes_with_caps_lock);
                         spin_unlock(&inode->i_lock);
 
-                        ceph_queue_cap_snap(ci,
-                                            ci->i_snap_realm->cached_context);
+                        ceph_queue_cap_snap(ci);
 
                         iput(inode);
                         continue;
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 65d12036b670..4c07acaf21e3 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -714,8 +714,7 @@ extern int ceph_update_snap_trace(struct ceph_mds_client *m,
 extern void ceph_handle_snap(struct ceph_mds_client *mdsc,
                              struct ceph_mds_session *session,
                              struct ceph_msg *msg);
-extern void ceph_queue_cap_snap(struct ceph_inode_info *ci,
-                                struct ceph_snap_context *snapc);
+extern void ceph_queue_cap_snap(struct ceph_inode_info *ci);
 extern int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
                                   struct ceph_cap_snap *capsnap);
 extern void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc);