在 2018年3月29日，下午8:54，Miklos Szeredi <miklos@xxxxxxxxxx> 写道： > > On Sat, Jan 20, 2018 at 7:32 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: >> On Sat, Jan 20, 2018 at 6:10 PM, Chengguang Xu <cgxu519@xxxxxxxxxx> wrote: >>> Inspired by encountering unexpected write error with >>> error code -EXDEV when upperdir and workdir having >>> different project quotas. The reason of the error is >>> project quota asks files in it strictly inherit >>> project id of it’s own, so rename/link operations >>> between those directories will fail and it may cause >>> failure during copy-up/index-link operations in overlayfs. >>> >>> So if upper filesystem supports O_TMPFILE, try to check >>> link ability between upperdir and workdir and if check >>> fails, print a proper warning message to indicate potential >>> possibility of write failure. >>> >>> The failure of the check does not directly lead to >>> read-only mounting because in some use cases may only >>> write to upperdir and do not modify anything in lowerdirs. > > Thinking about a bit more: this assumes that mounter has create > permission under upper layer root. That assumption would be true in > ordinary setups. But if we break that assumption and deny create in > the root of the upper layer, we could still have a perfectly working > setup (as long as there's no need to copy-up anything in that > directory). Isn’t it similar to the check which upperdir and workdir must be in same filesystem? If we set project quota then the related directories will behave like sub-filesystem. Thanks, Chengguang. > > So I'm not sure it's worth adding code for a check that is of dubious value. > > Thanks, > Miklos > -- > 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 -- 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
