On Mon, Oct 05, 2015 at 11:04:35AM -0700, Dave Hansen wrote: > > The warning comes out of ext4_walk_page_buffers() and the dirty state > comes from page_zero_new_buffers(). That seems a _bit_ goofy that the > filesystem is marking the page dirty and then so shortly warning about it. Yes, this is a bug in ext4 --- and in fact in ext3, which apparently we've lived with for *years*. The problem is that when we are journalling data buffers, we can't use page_zero_new_buffers(), because instead of calling mark_buffer_dirty(bh), we need to call ext4_handle_dirty_metadata(bh). This will call mark_buffer_dirty(bh) if journalling is not enabled, or if journalling is enabled, it will call jbd2_journal_dirty_metadata(handle,bh). Apprently it is extremely rare that (copied < len) --- especially when mm/filemap.c was doing a prefault. :-) So your patch looks good, but in addition to that, if copied is > 0 and less than len, we shouldn't be calling page_zero_new_buffers(). We're going to need our own version of it that doesn't call mark_buffer_dirty(). So if Linus wants to revert 998ef75ddb patch, we can do that, but I'm also happy applying your patch as a way of preventing the failure. We'll need to do more work to make ext4_journalled_write_end(), but that's a bigger change which I'd rather not do at this point in the development cycle. Thanks again for taking a closer look at things. I'm currently running a full soak test to make sure your patch to ext4_journalled_write_end() doesn't introduce any other problems, but I'm quite confident it should be fine. Cheers, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
