On Fri, Oct 11, 2019 at 08:24:14AM +0300, Alkis Georgopoulos wrote: > I'm not sure if this is an NFS issue, or a bindfs issue, or if I'm > not using the appropriate NFS options. > > I export my /home via NFS with: > > /home *(rw,async,crossmnt,no_subtree_check,no_root_squash,insecure) > > Inside my /home I'm providing a shared folder with a bindfs mount: > > bindfs -u 1000 --create-for-user=1000 -g 100 > --create-for-group=100 -p 770,af-x /home/share /home/share > > I.e. this just sets fixed permissions for anything under /home/share. > > And finally I mount /home on some NFS client (or on localhost): > > mount -t nfs server:/home /home > > The problem is that /home/share on the client doesn't show the > bindfs permissions, but it shows the underlying file system of the > server's /home/share. > The crossmnt NFS option follows submounts with other file systems, > but not with bindfs. > > On the other hand, if the bindfs source is on a different file > system than the bindfs target directory, everything works fine (i.e. > bindfs /other/filesystem/share /home/share). Huh. I wonder if nfsd is for some reason determining the existence of a mountpoint by comparing some kind of filesystem id and not seeing a change. Looking at the code to remind myself how this works.... nfsd_mountpoint() is using d_mountpoint() and follow_down(), which should be right. Then it's making an upcall to mountd. That's handled by nfs-utils/mountd/cache.c:nfsd_export(). The is_mountpoint() check there is indeed going to return false in your case because it's just comparing inode and device numbers.... But I think that case is only for the "mountpoint" export option. So I think all that matters is that export_matches() does the right thing, and it certainly looks like it does--it should succeed as long as there's a parent directory that's exported with crossmnt. There's some debugging you could try by looking at net/sunrpc/nfsd.*/content or using strace to watch rpc.mountd's reads and writes of net/sunrpc/nfsd.*/channel. What version of nfs-utils are you on? --b. > > Is there any way to configure either NFS or bindfs, so that this > works when I only have one partition, i.e. when the share is on the > same file system as /home? > > If anyone answers, please Cc me as I'm not in the list. > > Thank you very much, > Alkis Georgopoulos > LTSP developer
