[PATCH v3 0/4] ceph: support subvolume quarantine

[Alex Markuze <amarkuze@redhat.com>]

CephFS subvolume quarantine isolates a subvolume while allowing access
by recovery clients with q/Q MDS auth caps. The kernel client currently
does not advertise quarantine support, so the MDS can hold its requests
until quarantine is lifted.

This series handles MClientCaps v14 quarantine notifications, checks
cached data and metadata access, and handles disable notifications.
Fresh MDS replies allow recovery after a lost disable. It applies directly
to the base below and has no fscrypt prerequisite.

The first patch exports d_find_alias_rcu() to GPL modules. The remaining
three patches add the wire definitions, record quarantine state and
ancestry generations, then install the access checks before advertising
the session feature.

Changes since v2:
- Add the VFS export prerequisite to fix the undefined d_find_alias_rcu
  symbol reported by the kernel test robot with CONFIG_CEPH_FS=m.
  The fix carries Reported-by and Closes tags.
- Keep all three Ceph patches unchanged from v2.
- Replace object-only compile validation with a complete W=1 kernel and
  module build using GCC 14.2.0 and the robot's x86_64-rhel-9.4 config.

Validation:
A complete W=1 build with the kernel.org GCC 14.2.0 toolchain and the
robot's x86_64-rhel-9.4 config after olddefconfig passes. It produces
vmlinux, bzImage and all 2,233 configured modules, including ceph.ko and
libceph.ko. MODPOST succeeds, and Module.symvers contains the GPL export
of d_find_alias_rcu. Configuration changes are limited to olddefconfig's
toolchain capability normalization; there are no manual config changes.
W=1 warnings remain elsewhere in the kernel; none come from Ceph or
dcache.c.
All four patches pass strict checkpatch and apply in order to reproduce
the tested source tree. Seven deterministic source-extraction regression
runners pass; the ASan/UBSan/LSan VFS runner also demonstrates the remaining
cached encrypted-readlink bypass.

Known limitation: cached encrypted symlink targets can bypass quarantine
checks. fscrypt populates inode->i_link, which the VFS can use for readlink
or symlink traversal without calling Ceph's get_link operation. Uncached
encrypted targets and plaintext symlinks still pass through Ceph's checks.
Closing the encrypted-target cache gap needs the separate fscrypt support
and Ceph opt-in follow-up.

Live cluster, KASAN/lockdep, multi-MDS recovery and depth benchmarks have
not been run for this version. Existing snapshot mappings need server
notifications to revoke already installed PTEs. Disable messages carry
no generation, so same-rank ordering relies on ordered MDS delivery.
Recovery assumes the intended rwq/rwQ delegation; overlapping ordinary
rw and read-only q/Q grants still need server-side cap filtering.

v2: https://lore.kernel.org/r/cover.1792074165.git.amarkuze@redhat.com
Robot report:
https://lore.kernel.org/oe-kbuild-all/202610171220.i77KPiw5-lkp@intel.com/

Alex Markuze (4):
  dcache: export d_find_alias_rcu() for modular filesystems
  ceph: add subvolume quarantine wire definitions
  ceph: record subvolume quarantine from MDS cap updates
  ceph: fail quarantined subvolume access with EACCES

 fs/ceph/acl.c                |  28 +-
 fs/ceph/addr.c               |  72 ++-
 fs/ceph/caps.c               | 291 +++++++++++-
 fs/ceph/debugfs.c            |   1 +
 fs/ceph/dir.c                |  51 ++-
 fs/ceph/file.c               | 117 +++--
 fs/ceph/inode.c              | 841 ++++++++++++++++++++++++++++++++++-
 fs/ceph/ioctl.c              |  13 +
 fs/ceph/mds_client.c         |  23 +-
 fs/ceph/mds_client.h         |  26 +-
 fs/ceph/super.c              |   2 +
 fs/ceph/super.h              |  80 +++-
 fs/ceph/xattr.c              |  54 ++-
 fs/dcache.c                  |   1 +
 include/linux/ceph/ceph_fs.h |  13 +
 net/ceph/ceph_common.c       |   2 +
 16 files changed, 1482 insertions(+), 133 deletions(-)


base-commit: ed0502cb11f84fff29f374238e526ae94d9bdfde
-- 
2.34.1