On Tue, Dec 19, 2017 at 09:49:28AM +0800, Chengguang Xu wrote: > > > > 在 2017年12月19日，上午12:02，Vivek Goyal <vgoyal@xxxxxxxxxx> 写道： > > > > On Mon, Dec 18, 2017 at 08:55:48PM +0800, Chengguang Xu wrote: > >> Inspired by encountering unexpected write error when > >> upperdir and workdir having different project ids. > > > > Can you please make this problem descrition little better. By > > these two lines I really don't understand what's the problem > > you are trying to solve. All I understood was that upperdir > > and workdir had different project id. But not sure what > > problem it led to and why. > > > > In fact your first patch changelong was little better. It > > atleast said that you encounter "-EXDEV". So is it rename > > which fails. So rename is not allowed between two directories > > having different project ids? > > > > The background is > I encountered an unexpected write error with error code -EXDEV in > my environment which didn’t break any rules in overlayfs kernel > document. > > So I did some investigations and found when upperdir and workdir > having different project quotas then rename/link operations between > those directories would be fail with -EXDEV because project quota > asks files in it strictly inherit project id with it’s own. This will > make write fail during copy-up process. > > I wrote first patch to check this condition, but that check seems not > sufficient to detect write error, so after discussion with Amir, > we decided to check link ability between upperdir and workdir, it is > what copy-up actually doing when modifying files in lowerdirs, and also > I decided to only print a warning message instead of directly mounting > on read-only mode in case there is a special use case just read and do not > modify anything in lowerdirs. Ok, thanks for the explanation. I really wish that some of it makes to changelog so that somebody reading it later finds it much easier to understand. BTW, just curious, when upper supports O_TMPFILE, do we have to create tmpfile in workdir/. Can we create it in upper/ and then link in appropriate destination directory. Amir, is there a fundamental requirement about why tmpfile creation has to be in workdir. Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
