set_page_dirty/page_launder deadlock

[Marcelo Tosatti]

Hi,

While taking a look at page_launder()...

                 /* And re-start the thing.. */
                 spin_lock(&pagemap_lru_lock); 	<----------
                 if (result != 1)
                 	continue;
                 /* writepage refused to do anything */
                 set_page_dirty(page);
	      	 ^^^^^^^^^^^^^^^^^^^^
       		 goto page_active;
            }

set_page_dirty() may lock the pagecache_lock which means potential
deadlock since we have the pagemap_lru_lock locked.