Hi On Fri, Apr 11, 2014 at 3:43 PM, Tony Battersby <tonyb@xxxxxxxxxxxxxxx> wrote: > Exactly. For O_DIRECT, that would be the call to get_user_pages_fast() > from dio_refill_pages() in fs/direct-io.c, which is ultimately called > from blkdev_direct_IO(). If you drop mmap_sem after pinning a page without taking a write-ref, you break i_mmap_writable / VM_DENYWRITE. In memfd I rely on i_mmap_writable to work, same thing is done by exec() (and the old, now disabled, MAP_DENYWRITE). I don't know whether I should care. I mean, everyone pinning pages and writing to it without holding the mmap_sem has to take a write-ref for each page or it breaks i_mmap_writable. So this seems to be a bug in direct-IO, not in anyone relying on it, right? Thanks David -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
