ceph: fix freeing inode vs removing session caps race

remove_session_caps() uses iterate_session_caps() to remove caps,
but iterate_session_caps() skips inodes that are being deleted.
So session->s_nr_caps can be non-zero after iterate_session_caps()
return.

We can fix the issue by waiting until deletions are complete.
__wait_on_freeing_inode() is designed for the job, but it is not
exported, so we use lookup inode function to access it.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>

3 files changed, 41 insertions, 0 deletions

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 55aaddb4047e..3b0abed667c2 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -61,6 +61,14 @@ struct inode *ceph_get_inode(struct super_block *sb, struct ceph_vino vino)
         return inode;
 }
 
+struct inode *ceph_lookup_inode(struct super_block *sb, struct ceph_vino vino)
+{
+        struct inode *inode;
+        ino_t t = ceph_vino_to_ino(vino);
+        inode = ilookup5_nowait(sb, t, ceph_ino_compare, &vino);
+        return inode;
+}
+
 /*
  * get/constuct snapdir inode for a given directory
  */
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 6b40d8112c64..cbf08203e00d 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1031,6 +1031,37 @@ static void remove_session_caps(struct ceph_mds_session *session)
 {
         dout("remove_session_caps on %p\n", session);
         iterate_session_caps(session, remove_session_caps_cb, NULL);
+
+        spin_lock(&session->s_cap_lock);
+        if (session->s_nr_caps > 0) {
+                struct super_block *sb = session->s_mdsc->fsc->sb;
+                struct inode *inode;
+                struct ceph_cap *cap, *prev = NULL;
+                struct ceph_vino vino;
+                /*
+                 * iterate_session_caps() skips inodes that are being
+                 * deleted, we need to wait until deletions are complete.
+                 * __wait_on_freeing_inode() is designed for the job,
+                 * but it is not exported, so use lookup inode function
+                 * to access it.
+                 */
+                while (!list_empty(&session->s_caps)) {
+                        cap = list_entry(session->s_caps.next,
+                                         struct ceph_cap, session_caps);
+                        if (cap == prev)
+                                break;
+                        prev = cap;
+                        vino = cap->ci->i_vino;
+                        spin_unlock(&session->s_cap_lock);
+
+                        inode = ceph_lookup_inode(sb, vino);
+                        iput(inode);
+
+                        spin_lock(&session->s_cap_lock);
+                }
+        }
+        spin_unlock(&session->s_cap_lock);
+
         BUG_ON(session->s_nr_caps > 0);
         BUG_ON(!list_empty(&session->s_cap_flushing));
         cleanup_cap_releases(session);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index cbded572345e..afcd62a68916 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -677,6 +677,8 @@ extern void ceph_destroy_inode(struct inode *inode);
 
 extern struct inode *ceph_get_inode(struct super_block *sb,
                                     struct ceph_vino vino);
+extern struct inode *ceph_lookup_inode(struct super_block *sb,
+                                       struct ceph_vino vino);
 extern struct inode *ceph_get_snapdir(struct inode *parent);
 extern int ceph_fill_file_size(struct inode *inode, int issued,
                                u32 truncate_seq, u64 truncate_size, u64 size);