Use WARN rather than printk followed by WARN_ON(1), for conciseness.
A simplified version of the semantic patch that makes this transformation
is as follows: (http://coccinelle.lip6.fr/)
// <smpl>
@@
expression list es;
@@
-printk(
+WARN(1,
  es);
-WARN_ON(1);
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
        u64 search_start;
        int ret;
 
-       if (trans->transaction != root->fs_info->running_transaction) {
-               printk(KERN_CRIT "trans %llu running %llu\n",
+       if (trans->transaction != root->fs_info->running_transaction)
+               WARN(1, KERN_CRIT "trans %llu running %llu\n",
                       (unsigned long long)trans->transid,
                       (unsigned long long)
                       root->fs_info->running_transaction->transid);
-               WARN_ON(1);
-       }
-       if (trans->transid != root->fs_info->generation) {
-               printk(KERN_CRIT "trans %llu running %llu\n",
+
+       if (trans->transid != root->fs_info->generation)
+               WARN(1, KERN_CRIT "trans %llu running %llu\n",
                       (unsigned long long)trans->transid,
                       (unsigned long long)root->fs_info->generation);
-               WARN_ON(1);
-       }
 
        if (!should_cow_block(trans, root, buf)) {
                *cow_ret = buf;
        btrfs_set_header_nritems(left, old_left_nritems + push_items);
 
        /* fixup right node */
-       if (push_items > right_nritems) {
-               printk(KERN_CRIT "push items %d nr %u\n", push_items,
+       if (push_items > right_nritems)
+               WARN(1, KERN_CRIT "push items %d nr %u\n", push_items,
                       right_nritems);
-               WARN_ON(1);
-       }
 
        if (push_items < right_nritems) {
                push_space = btrfs_item_offset_nr(right, push_items - 1) -
 
        int was_dirty;
 
        btrfs_assert_tree_locked(buf);
-       if (transid != root->fs_info->generation) {
-               printk(KERN_CRIT "btrfs transid mismatch buffer %llu, "
+       if (transid != root->fs_info->generation)
+               WARN(1, KERN_CRIT "btrfs transid mismatch buffer %llu, "
                       "found %llu running %llu\n",
                        (unsigned long long)buf->start,
                        (unsigned long long)transid,
                        (unsigned long long)root->fs_info->generation);
-               WARN_ON(1);
-       }
        was_dirty = set_extent_buffer_dirty(buf);
        if (!was_dirty) {
                spin_lock(&root->fs_info->delalloc_lock);
 
                static DEFINE_RATELIMIT_STATE(_rs,
                                DEFAULT_RATELIMIT_INTERVAL,
                                /*DEFAULT_RATELIMIT_BURST*/ 2);
-               if (__ratelimit(&_rs)) {
-                       printk(KERN_DEBUG "btrfs: block rsv returned %d\n", ret);
-                       WARN_ON(1);
-               }
+               if (__ratelimit(&_rs))
+                       WARN(1, KERN_DEBUG "btrfs: block rsv returned %d\n",
+                            ret);
                ret = reserve_metadata_bytes(root, block_rsv, blocksize,
                                             BTRFS_RESERVE_NO_FLUSH);
                if (!ret) {
 
 {
        struct rb_node *node;
 
-       if (end < start) {
-               printk(KERN_ERR "btrfs end < start %llu %llu\n",
+       if (end < start)
+               WARN(1, KERN_ERR "btrfs end < start %llu %llu\n",
                       (unsigned long long)end,
                       (unsigned long long)start);
-               WARN_ON(1);
-       }
        state->start = start;
        state->end = end;
 
        }
 
        if (start + min_len > eb->len) {
-               printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
+               WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
                       "wanted %lu %lu\n", (unsigned long long)eb->start,
                       eb->len, start, min_len);
-               WARN_ON(1);
                return -EINVAL;
        }
 
 
                                    extent_map_end(em) - 1, NULL, GFP_NOFS);
                goto insert;
        } else {
-               printk(KERN_ERR "btrfs unknown found_type %d\n", found_type);
-               WARN_ON(1);
+               WARN(1, KERN_ERR "btrfs unknown found_type %d\n", found_type);
        }
 not_found:
        em->start = start;
 
         * the log must never go across transaction boundaries.
         */
        smp_mb();
-       if (!list_empty(&fs_info->tree_mod_seq_list)) {
-               printk(KERN_ERR "btrfs: tree_mod_seq_list not empty when "
+       if (!list_empty(&fs_info->tree_mod_seq_list))
+               WARN(1, KERN_ERR "btrfs: tree_mod_seq_list not empty when "
                        "creating a fresh transaction\n");
-               WARN_ON(1);
-       }
-       if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log)) {
-               printk(KERN_ERR "btrfs: tree_mod_log rb tree not empty when "
+       if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log))
+               WARN(1, KERN_ERR "btrfs: tree_mod_log rb tree not empty when "
                        "creating a fresh transaction\n");
-               WARN_ON(1);
-       }
        atomic_set(&fs_info->tree_mod_seq, 0);
 
        spin_lock_init(&cur_trans->commit_lock);
 
                cur = cur->next;
 
                if (!device->writeable) {
-                       printk(KERN_ERR
+                       WARN(1, KERN_ERR
                               "btrfs: read-only device in alloc_list\n");
-                       WARN_ON(1);
                        continue;
                }