Hi, I'm working on some new Smatch code and it complains about this
patch from last year. -Dan

----
This is a semi-automatic email about new static checker warnings.

The patch 7414a03fbf9e: "btrfs: initial readahead code and 
prototypes" from May 23, 2011, leads to the following Smatch 
complaint:

fs/btrfs/reada.c:147 __readahead_hook()
         error: we previously assumed 'eb' could be null (see line 122)

fs/btrfs/reada.c
   121  
   122          if (eb)
                   ^^^^
Checked here.

   123                  level = btrfs_header_level(eb);
   124  
   125          /* find extent */
   126          spin_lock(&fs_info->reada_lock);
   127          re = radix_tree_lookup(&fs_info->reada_tree, index);
   128          if (re)
   129                  kref_get(&re->refcnt);
   130          spin_unlock(&fs_info->reada_lock);
   131  
   132          if (!re)
   133                  return -1;
   134  
   135          spin_lock(&re->lock);
   136          /*
   137           * just take the full list from the extent. afterwards we
   138           * don't need the lock anymore
   139           */
   140          list_replace_init(&re->extctl, &list);
   141          for_dev = re->scheduled_for;
   142          re->scheduled_for = NULL;
   143          spin_unlock(&re->lock);
   144  
   145          if (err == 0) {
   146                  nritems = level ? btrfs_header_nritems(eb) : 0;
                                  ^^^^^
Checked here again indirectly.

   147                  generation = btrfs_header_generation(eb);
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Dereferenced inside function without checking.

   148                  /*
   149                   * FIXME: currently we just set nritems to 0 if this is 
a leaf,

regards,
dan carpenter

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