Overlayfs inodes are considered unstable in several aspects, because on a copy up event: 1. st_ino can change 2. st_dev can change 3. hardlinks are broken 4. NFS handle would become stale 5. content of read-only file descriptor would become stale This patch set 'stabilizes' overlayfs inodes w.r.t. st_ino/st_dev and takes some big steps in the direction of stabilizing hardlinks and NFS handles. The full work is available at [1] and includes also an untested WIP for NFS export support. This work relies heavily on inode and dentry cache - so long as the overlayfs dcache is fully populated, hardlinks should never be broken and NFS handles should never become stale on copy up. The missing piece of the puzzle is a persistent mapping from lower entries to upper entries, so that overlay entries could be reconstructed from their stable (lower) unique identifier. But the work has merit even without the missing piece, because it stabilizes st_ino/st_dev and prevents breaking hardlinks in many use cases. [1] https://github.com/amir73il/linux/commits/ovl-nfs-export Amir Goldstein (13): ovl: check if all layers are on the same fs ovl: redirect dir by file handle on copy up ovl: lookup redirect by file handle ovl: store file handle of stable inode ovl: lookup stable inode by file handle ovl: move inode helpers to inode.c ovl: create helpers for initializing hashed inode ovl: allow hashing non upper inodes ovl: inherit overlay inode ino/generation from real inode ovl: hash overlay inodes by stable inode ovl: fix du --one-file-system on overlay mount ovl: constant ino across copy up ovl: try to hardlink upper on copy up of lower hardlinks fs/overlayfs/Kconfig | 16 ++++ fs/overlayfs/copy_up.c | 130 ++++++++++++++++++++++++++- fs/overlayfs/dir.c | 2 +- fs/overlayfs/inode.c | 106 ++++++++++++++++++++-- fs/overlayfs/namei.c | 226 ++++++++++++++++++++++++++++++++++++++++++----- fs/overlayfs/overlayfs.h | 40 +++++++-- fs/overlayfs/ovl_entry.h | 4 +- fs/overlayfs/readdir.c | 85 ++++++++++++++++-- fs/overlayfs/super.c | 37 +++++++- fs/overlayfs/util.c | 51 +++++++---- 10 files changed, 633 insertions(+), 64 deletions(-) -- 2.7.4
