verity: use atomic_set instead of atomic_cmpxchg in read_completed

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 423 matching lines @@
 }
 
 /**
  * dm_bht_read_completed
  * @entry:      pointer to the entry that's been loaded
  * @status:     I/O status. Non-zero is failure.
  * MUST always be called after a read_cb completes.
  */
 void dm_bht_read_completed(struct dm_bht_entry *entry, int status)
 {
-        int state;
         if (status) {
                 /* TODO(wad) add retry support */
                 DMCRIT("an I/O error occurred while reading entry");
                 atomic_set(&entry->state, DM_BHT_ENTRY_ERROR_IO);
                 /* entry->nodes will be freed later */
                 return;
         }
-        state = atomic_cmpxchg(&entry->state,
-                                   DM_BHT_ENTRY_PENDING,
-                                   DM_BHT_ENTRY_READY);
-        if (state != DM_BHT_ENTRY_PENDING) {
-                DMCRIT("state changed on entry out from under io");
-                BUG();
-        }
+        BUG_ON(atomic_read(&entry->state) != DM_BHT_ENTRY_PENDING);
+        atomic_set(&entry->state, DM_BHT_ENTRY_READY);
 }
 EXPORT_SYMBOL(dm_bht_read_completed);
 
 /**
  * dm_bht_write_completed
  * @entry:      pointer to the entry that's been loaded
  * @status:     I/O status. Non-zero is failure.
  * Should be called after a write_cb completes. Currently only catches
  * errors which more writers don't care about.
  */
@@ skipping 720 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);