ceph: acquire i_mutex in __ceph_do_pending_vmtruncate

make __ceph_do_pending_vmtruncate() acquire the i_mutex if the caller
does not hold the i_mutex, so ceph_aio_read() can call safely.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index be2f262..eeac43d 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1453,7 +1453,7 @@
 
 
 /*
- * called by trunc_wq; take i_mutex ourselves
+ * called by trunc_wq;
  *
  * We also truncate in a separate thread as well.
  */
@@ -1464,9 +1464,7 @@
 	struct inode *inode = &ci->vfs_inode;
 
 	dout("vmtruncate_work %p\n", inode);
-	mutex_lock(&inode->i_mutex);
-	__ceph_do_pending_vmtruncate(inode);
-	mutex_unlock(&inode->i_mutex);
+	__ceph_do_pending_vmtruncate(inode, true);
 	iput(inode);
 }
 
@@ -1490,12 +1488,10 @@
 }
 
 /*
- * called with i_mutex held.
- *
  * Make sure any pending truncation is applied before doing anything
  * that may depend on it.
  */
-void __ceph_do_pending_vmtruncate(struct inode *inode)
+void __ceph_do_pending_vmtruncate(struct inode *inode, bool needlock)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
 	u64 to;
@@ -1528,7 +1524,11 @@
 	     ci->i_truncate_pending, to);
 	spin_unlock(&ci->i_ceph_lock);
 
+	if (needlock)
+		mutex_lock(&inode->i_mutex);
 	truncate_inode_pages(inode->i_mapping, to);
+	if (needlock)
+		mutex_unlock(&inode->i_mutex);
 
 	spin_lock(&ci->i_ceph_lock);
 	if (to == ci->i_truncate_size) {
@@ -1581,7 +1581,7 @@
 	if (ceph_snap(inode) != CEPH_NOSNAP)
 		return -EROFS;
 
-	__ceph_do_pending_vmtruncate(inode);
+	__ceph_do_pending_vmtruncate(inode, false);
 
 	err = inode_change_ok(inode, attr);
 	if (err != 0)
@@ -1763,7 +1763,7 @@
 	     ceph_cap_string(dirtied), mask);
 
 	ceph_mdsc_put_request(req);
-	__ceph_do_pending_vmtruncate(inode);
+	__ceph_do_pending_vmtruncate(inode, false);
 	return err;
 out:
 	spin_unlock(&ci->i_ceph_lock);