NFSv4.1: Balance pnfs_layout_hdr refcount in pnfs_layout_(insert|remove)_lseg

Ensure that the reference count for pnfs_layout_hdr reverts to the
original value after a call to pnfs_layout_remove_lseg().

Note that the caller is expected to hold a reference to the struct
pnfs_layout_hdr.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/pnfs.c

@@ -320,8 +320,6 @@ static void pnfs_free_lseg(struct pnfs_layout_segment *lseg)
 	struct inode *ino = lseg->pls_layout->plh_inode;
 
 	NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
-	/* Matched by pnfs_get_layout_hdr in pnfs_layout_insert_lseg */
-	pnfs_put_layout_hdr(NFS_I(ino)->layout);
 }
 
 static void
@@ -332,6 +330,8 @@ pnfs_layout_remove_lseg(struct pnfs_layout_hdr *lo,
 
 	WARN_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
 	list_del_init(&lseg->pls_list);
+	/* Matched by pnfs_get_layout_hdr in pnfs_layout_insert_lseg */
+	atomic_dec(&lo->plh_refcount);
 	if (list_empty(&lo->plh_segs))
 		set_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags);
 	rpc_wake_up(&NFS_SERVER(inode)->roc_rpcwaitq);
@@ -352,9 +352,11 @@ pnfs_put_lseg(struct pnfs_layout_segment *lseg)
 	lo = lseg->pls_layout;
 	inode = lo->plh_inode;
 	if (atomic_dec_and_lock(&lseg->pls_refcount, &inode->i_lock)) {
+		pnfs_get_layout_hdr(lo);
 		pnfs_layout_remove_lseg(lo, lseg);
 		spin_unlock(&inode->i_lock);
 		pnfs_free_lseg(lseg);
+		pnfs_put_layout_hdr(lo);
 	}
 }
 EXPORT_SYMBOL_GPL(pnfs_put_lseg);