2018-03-16 15:23 GMT+08:00 Amir Goldstein <amir73il@xxxxxxxxx>: > On Fri, Mar 16, 2018 at 8:25 AM, Eddie Horng <eddiehorng.tw@xxxxxxxxx> wrote: >> 2018-03-16 5:48 GMT+08:00 Amir Goldstein <amir73il@xxxxxxxxx>: >>> On Thu, Mar 15, 2018 at 8:40 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: >>>> On Thu, Mar 15, 2018 at 4:30 PM, Eddie Horng <eddiehorng.tw@xxxxxxxxx> wrote: >>> [...] >>>> The problem *is* with nfsd+overlayfs, because nfsd verifies >>>> in compose_entry_fh() that (dchild->d_inode->i_ino == ino), but it is not. >>>> In that case, encode_entryplus_baggage() falls back to encoding xdr_zero. >>>> In overlayfs stat.st_ino is consistent with readdir d_ino since kernel version >>>> v4.15 and only for all layers on the same fs. >>>> >>>> However, there is no guaranty that inode->i_ino is the same as stat.st_ino. >>>> Overlayfs exposes only stat.st_ino to user (as well as readdir d_ino), but >>>> never (to my knowledge) does it expose inode->i_ino. >>>> >>>> There was a nfsd fix for a somewhat similar problem that went into v4.16-rc1: >>>> 76c479480b9a nfsd: encode stat->mtime for getattr instead of inode->i_mtime >>>> >>>> The solution to the problem is to either convert all references of >>>> nfsd to i_inode >>>> with references to st_ino, or make sure to set inode->i_ino correctly for >>>> overlayfs inodes. >>>> >>>> From first glimps, the change in nfsd looks non trivial. >>>> The change to overlayfs seems doable, but didn't look closely yet. >>>> Will try to come up with test patch for you. >>>> >>> >>> Eddie, >>> >>> Please try this patch. It worked for me. >>> >>> Thanks, >>> Amir. >> >> Hi Amir, >> The patch works like a charm in my first test, but when I switch lower >> layer to different fs then upper and merged, problem comes again. The > > Yes, that is expected. As I explained, overlayfs does NOT guaranty consistency > of d_ino to st_ino with non-samefs and this patch doesn't change that. > Apparently, the consequence is that with NFSv3 you will get DT_UNKNOWN. > > If this is really a problem for your use case, I have already posted a solution > for non-samefs while back https://github.com/amir73il/linux/commits/ovl-xino > I can rebase and re-post if you are interested in testing. > Can I assume from your test example that you are interested in the setup of > ext4 as upper/lower (but non samefs)? Because solving the problem for ext4 > (32bit ino) is a bit simpler than the general case (64bit ino). > > Thanks, > Amir. My setup for upper is ext4, lower however is a proprietary fs, whose ino is 32bit. So far it has identical behavior as ext4 to work with overlay. I'm glad to test if the solution works for ext4 or the proprietary fs. In the other hand, I also try to submit a request to Google to see if the build tool can handle DT_UNKNOWN properly, after all the application use d_type should do that. thanks, Eddie -- 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
