Re: [PATCH v2 00/20] Overlayfs inodes index

J. Bruce Fields
2017-06-07T17:17:45Z

On Wed, Jun 07, 2017 at 10:51:04AM +0300, Amir Goldstein wrote:
> Miklos,
>
> This set is an independent series a top of current overlayfs-next.
> I yanked all the dependencies from previous postings (consistent d_ino,
> dir_lock, verify_lower) and included everything needed in this posting.
>
> This work introcuding the inodes index opt-in feature, which provides:
> - Hardlinks are not broken on copy up
> - Infrastructure for overlayfs NFS export

Minor suggestion: for the lazy readers among us, a quick summary of the
implementation might be helpful. (Could take most of it from just
05/20?)

--b.

>
> Hardlink copy up tests including concurrent copy up of lower hardlinks
> are available on my xfstests dev branch [1].
>
> There are some more TODO items before this is ready for v4.13, but I'd
> love to hear what you think about the direction this has taken so far.
>
> Thanks,
> Amir.
>
> TODO:
> - Consistency of lower and upper hardlinks (*)
> - Cleanup stale and orphan index entries on mount (**)
> - Document the inodes index feature
>
> (*) When any lower hardlink has been copied up, we get the indexed
> upper inode on lookup of all lower hardlinks and since they all
> share the same overlay inode, they have the same 'realinode'.
> Opening the lower hardlinks for read gives that lower inode
> and not the indexed upper 'realinode'. The tests in [1] demostrate
> this problem.
> (**) A stale index entry has a missing or stale 'origin' xattr. An
> orphan index entry has nlink 1 and all lower hardlinks are covered.
>
> v2:
> - Rebase on top of overalyfs-next with all dependencies
> - Remove 'verify_lower' dependency and simplify
> - Lookup index dentry on ovl_lookup()
> - Don't hash broken overlay hardlinks by origin
> - Fix nlink count of overlay inodes
> - Constant st_ino for indexed hardlinks
>
> v1:
> - Upper/work dir exclusive lock
> - Introduce verify_lower mount option
> - Hash overlay inodes by origin
> - Introduce inodes index feature
> - Copy up hardlinks using inodes index
>
> [1] https://github.com/amir73il/xfstests/commits/overlayfs-devel
>
> Amir Goldstein (20):
> vfs: introduce inode 'inuse' lock
> ovl: get exclusive ownership on upper/work dirs
> ovl: relax same fs constrain for ovl_check_origin()
> ovl: generalize ovl_create_workdir()
> ovl: introduce the inodes index dir feature
> ovl: verify upper root dir matches lower root dir
> ovl: verify index dir matches upper dir
> ovl: lookup index entry for non-dir
> ovl: move inode helpers to inode.c
> ovl: use ovl_inode_init() for initializing new inode
> ovl: hash overlay non-dir inodes by copy up origin inode
> ovl: fix nlink leak in ovl_rename()
> ovl: adjust overlay inode nlink for indexed inodes
> ovl: defer upper dir lock to tempfile link
> ovl: factor out ovl_copy_up_inode() helper
> ovl: generalize ovl_copy_up_locked() using actors
> ovl: generalize ovl_copy_up_one() using actors
> ovl: implement index dir copy up method
> ovl: handle race of concurrent lower hardlinks copy up
> ovl: constant inode number for hardlinks
>
> fs/inode.c | 74 ++++++
> fs/overlayfs/Kconfig | 20 ++
> fs/overlayfs/copy_up.c | 648 ++++++++++++++++++++++++++++++++++++++---------
> fs/overlayfs/dir.c | 23 +-
> fs/overlayfs/inode.c | 138 +++++++++-
> fs/overlayfs/namei.c | 241 +++++++++++++++---
> fs/overlayfs/overlayfs.h | 52 ++--
> fs/overlayfs/ovl_entry.h | 7 +
> fs/overlayfs/super.c | 194 ++++++++++++--
> fs/overlayfs/util.c | 45 ++--
> include/linux/fs.h | 16 ++
> 11 files changed, 1235 insertions(+), 223 deletions(-)
>
> --
> 2.7.4