[PATCH v2 00/13] Overlayfs lazy lookup of lowerdata

[Amir Goldstein <amir73il@gmail.com>]

Miklos,

This v2 combines the prep patch set [1] and lazy lookup patch set [2].

This work is motivated by Alexander's composefs use case.
Alexander has been developing and testing his fsverity patches over
my lazy-lowerdata-lookup branch [3].

Alexander has also written tests for lazy lowerdata lookup [4].

Note that patch #1 is a Fixes patch for stable.
Gao commented that the fix may not be complete, but I think it is better
than no fix at all.

Regarding lazy lookup in d_real(), I am not sure if the best effort
lookup is the best solution, but in any case, none of this code kicks in
without explicit opt-in to data-only layers, so the risk of breaking
existing setups is quite low.

Thanks,
Amir.

Changes since v1:
- Include the prep patch set
- Split remove lowerdata from add lowerdata_redirect patch
- Remove embedded ovl_entry stack optimization
- Add lazy lookup and comment in d_real_inode()
- Improve documentation of :: data-only layers syntax
- Added RVBs

[1] https://lore.kernel.org/linux-unionfs/20230408164302.1392694-1-amir73il@gmail.com/
[2] https://lore.kernel.org/linux-unionfs/20230412135412.1684197-1-amir73il@gmail.com/
[3] https://github.com/amir73il/linux/commits/ovl-lazy-lowerdata
[4] https://github.com/amir73il/xfstests/commits/ovl-lazy-lowerdata

Amir Goldstein (13):
  ovl: update of dentry revalidate flags after copy up
  ovl: use OVL_E() and OVL_E_FLAGS() accessors
  ovl: use ovl_numlower() and ovl_lowerstack() accessors
  ovl: factor out ovl_free_entry() and ovl_stack_*() helpers
  ovl: move ovl_entry into ovl_inode
  ovl: deduplicate lowerpath and lowerstack[]
  ovl: deduplicate lowerdata and lowerstack[]
  ovl: remove unneeded goto instructions
  ovl: introduce data-only lower layers
  ovl: implement lookup in data-only layers
  ovl: prepare to store lowerdata redirect for lazy lowerdata lookup
  ovl: prepare for lazy lookup of lowerdata inode
  ovl: implement lazy lookup of lowerdata in data-only layers

 Documentation/filesystems/overlayfs.rst |  36 +++++
 fs/overlayfs/copy_up.c                  |  11 ++
 fs/overlayfs/dir.c                      |   3 +-
 fs/overlayfs/export.c                   |  41 +++---
 fs/overlayfs/file.c                     |  21 ++-
 fs/overlayfs/inode.c                    |  38 +++--
 fs/overlayfs/namei.c                    | 185 +++++++++++++++++++-----
 fs/overlayfs/overlayfs.h                |  20 ++-
 fs/overlayfs/ovl_entry.h                |  73 ++++++++--
 fs/overlayfs/super.c                    | 132 ++++++++++-------
 fs/overlayfs/util.c                     | 165 ++++++++++++++++-----
 11 files changed, 534 insertions(+), 191 deletions(-)

-- 
2.34.1