dcache: Fix locking bugs in backported "deal with deadlock in d_walk()"

[firefly-linux-kernel-4.4.55.git] / fs / nfs / nfs4filelayoutdev.c

diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
index 1fe284f01f8b6419b3c7a9a5728ea5fc33cad583..678cb8964532244bfd661568e9993966d85ff9f2 100644 (file)
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -775,34 +775,56 @@ nfs4_fl_select_ds_fh(struct pnfs_layout_segment *lseg, u32 j)
        return flseg->fh_array[i];
 }
 
+static void nfs4_wait_ds_connect(struct nfs4_pnfs_ds *ds)
+{
+       might_sleep();
+       wait_on_bit(&ds->ds_state, NFS4DS_CONNECTING,
+                       nfs_wait_bit_killable, TASK_KILLABLE);
+}
+
+static void nfs4_clear_ds_conn_bit(struct nfs4_pnfs_ds *ds)
+{
+       smp_mb__before_clear_bit();
+       clear_bit(NFS4DS_CONNECTING, &ds->ds_state);
+       smp_mb__after_clear_bit();
+       wake_up_bit(&ds->ds_state, NFS4DS_CONNECTING);
+}
+
+
 struct nfs4_pnfs_ds *
 nfs4_fl_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx)
 {
        struct nfs4_file_layout_dsaddr *dsaddr = FILELAYOUT_LSEG(lseg)->dsaddr;
        struct nfs4_pnfs_ds *ds = dsaddr->ds_list[ds_idx];
        struct nfs4_deviceid_node *devid = FILELAYOUT_DEVID_NODE(lseg);
-
-       if (filelayout_test_devid_unavailable(devid))
-               return NULL;
+       struct nfs4_pnfs_ds *ret = ds;
 
        if (ds == NULL) {
                printk(KERN_ERR "NFS: %s: No data server for offset index %d\n",
                        __func__, ds_idx);
                filelayout_mark_devid_invalid(devid);
-               return NULL;
+               goto out;
        }
+       if (ds->ds_clp)
+               goto out_test_devid;
 
-       if (!ds->ds_clp) {
+       if (test_and_set_bit(NFS4DS_CONNECTING, &ds->ds_state) == 0) {
                struct nfs_server *s = NFS_SERVER(lseg->pls_layout->plh_inode);
                int err;
 
                err = nfs4_ds_connect(s, ds);
-               if (err) {
+               if (err)
                        nfs4_mark_deviceid_unavailable(devid);
-                       return NULL;
-               }
+               nfs4_clear_ds_conn_bit(ds);
+       } else {
+               /* Either ds is connected, or ds is NULL */
+               nfs4_wait_ds_connect(ds);
        }
-       return ds;
+out_test_devid:
+       if (filelayout_test_devid_unavailable(devid))
+               ret = NULL;
+out:
+       return ret;
 }
 
 module_param(dataserver_retrans, uint, 0644);