CHROMIUM: verity: use atomic_set instead of atomic_cmpxchg in verify_path

drivers/md/dm-bht.c

  /*
  * Copyright (C) 2010 The Chromium OS Authors <chromium-os-dev@chromium.org>
  *
  * Device-Mapper block hash tree interface.
  * See Documentation/device-mapper/dm-bht.txt for details.
  *
  * This file is released under the GPL.
  */
 
 #include <asm/atomic.h>
@@ skipping 676 matching lines @@
 
                 /* Keep the containing block of hashes to be verified in the
                  * next pass.
                  */
                 block = entry->nodes;
         } while (--depth > 0 && state != DM_BHT_ENTRY_VERIFIED);
 
         /* Mark path to leaf as verified. */
         for (depth++; depth < bht->depth; depth++) {
                 entry = dm_bht_get_entry(bht, depth, block_index);
-                atomic_cmpxchg(&entry->state,
-                               DM_BHT_ENTRY_READY,
-                               DM_BHT_ENTRY_VERIFIED);
+                /* At this point, entry can only be in VERIFIED or READY state.
+                 * So it is safe to use atomic_set instead of atomic_cmpxchg.
+                 */
+                atomic_set(&entry->state, DM_BHT_ENTRY_VERIFIED);
         }
 
         DMDEBUG("verify_path: node %u is verified to root", block_index);
         return 0;
 
 mismatch:
         DMERR("verify_path: failed to verify hash against parent (d=%u,bi=%u)",
               depth, block_index);
         return DM_BHT_ENTRY_ERROR_MISMATCH;
 }
@@ skipping 478 matching lines @@
                 DMERR("no root digest exists to export");
                 if (available > 0)
                         *hexdigest = 0;
                 return -1;
         }
         dm_bht_bin_to_hex(bht->root_digest, hexdigest, bht->digest_size);
         return 0;
 }
 EXPORT_SYMBOL(dm_bht_root_hexdigest);