Miklos, This is the second part of the work to support fanotify reporting of events with file ids on overlayfs. The fanotify_event_info_fid struct reported with fanotify events has an object file handle and an fsid, so fanotify requires that filesystems can encode file handles and have a non-zero f_fsid. The first part [1] that was merged to v6.5-rc1, relaxed the fanotify requirements for filesystems to support reporting events with fid to require only the ->encode_fh() export operation. Patch 1 changes overlayfs export_operations to meet the new requirements with the default overlay configurations (i.e. no need for nfs_export=on), thus, allowing an fanotify watch with FAN_REPORT_FID on overlayfs. There are LTS tests [2] for fanotify(FAN_REPORT_FID) + overlayfs. Patches 2-4 are not strcitly needed to support reporting fanotify events with fid, because overlayfs already reports a non-zero f_fsid, it's just not a unique fsid. So before allowing to report events with overlayfs fids, I wanted to fix overlayfs fsid to be more unique. I wanted to implement a persistent and unique fsid for overlayfs. I wanted it to be the default behavior, but needed to avoid breaking applications that rely on an existing overlayfs fsid to persist. I came up with a solution that is described in patch 4 (uuid=auto) that meets all the requirement above. There is an xfstest to test the persistent-unique fsid feature [3]. This patch set has been in overlayfs-next for soaking since v6.5-rc1. If you have any reservations that we will not be able to resolve in time for 6.6, especially regarding the on-disk format and backward compat, we could also merge only patch 1 and leave the fsid patches for later. Thanks, Amir. [1] https://lore.kernel.org/linux-fsdevel/20230425130105.2606684-1-amir73il@xxxxxxxxx/ [2] https://github.com/amir73il/ltp/commits/ovl_encode_fid [3] https://github.com/amir73il/xfstests/commits/ovl_fsid Amir Goldstein (4): ovl: support encoding non-decodable file handles ovl: add support for unique fsid per instance ovl: store persistent uuid/fsid with uuid=on ovl: auto generate uuid for new overlay filesystems Documentation/filesystems/overlayfs.rst | 25 ++++++++++ fs/overlayfs/copy_up.c | 2 +- fs/overlayfs/export.c | 26 ++++++++--- fs/overlayfs/inode.c | 2 +- fs/overlayfs/namei.c | 5 +- fs/overlayfs/overlayfs.h | 22 +++++++++ fs/overlayfs/ovl_entry.h | 3 +- fs/overlayfs/params.c | 31 +++++++++++-- fs/overlayfs/super.c | 29 ++++++++++-- fs/overlayfs/util.c | 61 +++++++++++++++++++++++++ 10 files changed, 186 insertions(+), 20 deletions(-) -- 2.34.1
