On Fri, Jul 08, 2016 at 06:01:49PM +0200, David Sterba wrote: > On Fri, Jun 03, 2016 at 12:08:38PM -0700, Liu Bo wrote: > > eb->io_pages is set in read_extent_buffer_pages(). > > > > In case of readpage failure, for pages that have been added to bio, > > it calls bio_endio and later readpage_io_failed_hook() does the work. > > > > When this eb's page (couldn't be the 1st page) fails to add itself to bio > > due to failure in merge_bio(), it cannot decrease eb->io_pages via > > bio_endio, > > and ends up with a memory leak eventually. > > > > This lets __do_readpage propagate errors to callers and adds the > > 'atomic_dec(&eb->io_pages)'. > > I'm not sure, but could we lose some error values from __do_readpage? > Ie. return 0 even if there was an error in a page that's in the middle > (not the first, not the last). > > The loop in __do_readpage iterates while (cur <= end), and ret is only > set by submit_extent_page, but the loop does not exit immediatelly. So > we can detect error, set page error state bit, but next loop will > overwrite ret with 0 (if the page submission was ok). > > Then we still don't decrement the io_pages as needed.
Right, it still has that problem, then the possible way I can see is to break the while (cur <= end) loop when we fail on submit_extent_page() and pass an error up to its caller and we can do the rest eb->io_pages cleanup work in read_extent_buffer_pages(), just like how we did in write_one_eb() (this was already suggested by Josef, but seems I was off the right track). This also assumes that if one page fails on submit_extent_page(), it's likely for the rest pages to fail as well. What do you think? Thanks, -liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
