Hi, > On 6/21/21 3:41 PM, Wang Yugui wrote: > > Hi, > > > >> OK thanks for the information. I think they will just work in nfs-ganesha as > >> long as the snapshots or subvols are mounted within an nfs-ganesha export or > >> are exported explicitly. nfs-ganesha has the equivalent of knfsd's > >> nohide/crossmnt options and when nfs-ganesha detects crossing a filesystem > >> boundary will lookup the filesystem via getmntend and listing btrfs subvols > >> and then expose that filesystem (via the fsid attribute) to the clients > >> where at least the Linux nfs client will detect a filesystem boundary and > >> create a new mount entry for it. > > > > Not only exported explicitly, but also kept in the same hierarchy. > > > > If we export > > /mnt/test #the btrfs > > /mnt/test/sub1 # the btrfs subvol 1 > > /mnt/test/sub2 # the btrfs subvol 2 > > > > we need to make sure we will not access '/mnt/test/sub1' through '/mnt/test' > > from nfs client. > > > > current safe export: > > #/mnt/test #the btrfs, not exported > > /mnt/test/sub1 # the btrfs subvol 1 > > /mnt/test/sub2 # the btrfs subvol 2 > > > > What's the problem with exporting /mnt/test AND then exporting sub1 and sub2 as crossmnt exports? As far as I can tell, that seems to work just fine with nfs-ganesha. I'm not sure what will happen on nfs-ganesha. crossmnt(kernel nfsd) failed to work when exporting /mnt/test,/mnt/test/sub1, /mnt/test/sub2. # /bin/find /nfs/test/ /nfs/test/ find: File system loop detected; ‘/nfs/test/sub1’ is part of the same file system loop as ‘/nfs/test/’. /nfs/test/.snapshot find: File system loop detected; ‘/nfs/test/.snapshot/sub1-s1’ is part of the same file system loop as ‘/nfs/test/’. find: File system loop detected; ‘/nfs/test/.snapshot/sub2-s1’ is part of the same file system loop as ‘/nfs/test/’. /nfs/test/dir1 /nfs/test/dir1/a.txt find: File system loop detected; ‘/nfs/test/sub2’ is part of the same file system loop as ‘/nfs/test/’ /bin/find report 'File system loop detected', it means that vfs cache( based on st_dev + st_ino?) on nfs client side will have some problem? In fact, I was exporting /mnt/test for years too. but btrfs subvols means multiple filesystems(different st_dev), in theory, we needs to use it based on nfs crossmnt. Best Regards Wang Yugui (wangyugui@xxxxxxxxxxxx) 2021/06/23
