[PATCH 0/7] smb: client: remount reconfigure option fixes

From: Rajasi Mandal <[email protected]>

This series makes several mount options actually take effect (or be
cleanly rejected) on remount instead of being silently ignored, and
fixes the option-comparison baseline so a bare 'mount -o remount' is
neither wrongly rejected nor allowed to clobber live runtime state.

Overview:
  1: build the reconfigure baseline from the live mount (a private,
     runtime-synced dup of cifs_sb->ctx) instead of init defaults.
  2: reject connection-tied options that cannot change on remount,
     using that baseline so bare remounts and /proc/mounts replays
     are still accepted.
  3: propagate retrans to the live server on remount.
  4: reject cache=ro / cache=singleclient changes on remount.
  5: apply rasize on remount.
  6: move struct tcon_list to cifsglob.h (no functional change).
  7: make nolease take effect on remount and evict lease-bearing
     cached state.

Changes since the previous posting ("[PATCH RESEND 0/9]"):
  - Folded the two "review fixes" commits into the patches they fix;
    the series is now 7 self-contained, bisectable patches.
  - Patch 1: do not fabricate no_linux_ext (mirrors the existing
    nopersistent handling); sync the server-shared display fields into
    the baseline so a bare remount on a shared connection is not
    wrongly rejected.
  - Patch 7: invalidate_all_cached_dirs_sb() counts tcons and
    allocates with GFP_KERNEL outside tlink_tree_lock instead of a
    per-tcon GFP_ATOMIC allocation that could fail mid-walk.

Known pre-existing issues intentionally NOT addressed here (each is
called out in the relevant commit message):
  - cifs_sb->ctx is read locklessly while smb3_reconfigure() overwrites
    it in-place, so a /proc/mounts read racing a remount of the same
    mount can observe a torn pointer.  This predates the series; the
    proper fix (RCU-style ctx replacement) is left as its own change.
    (Patch 1)
  - tcon->unix_ext shares a bitfield word with other lockless writers;
    theoretical word-tearing only.  (Patch 1)
  - Explicit 'mount -o remount,port=<active-default>' is rejected; not
    reachable via tooling since port is not in /proc/mounts.  (Patch 2)
  - cached_dir_lease_break() updates tcon->tc_count without tc_lock;
    cfids_laundromat_worker() can resurrect a tcon from tc_count 0
    while cifs_put_tcon() tears it down; and the cifs_debug dirs knob
    invalidates with close_handles=false.  All pre-existing and
    unrelated to nolease.  (Patch 7)

Testing:
  - checkpatch --strict clean (bar one pre-existing CamelCase CHECK on
    ses->domainName); each patch builds standalone (bisectable).
  - Functional testing on Azure Files (SMB 3.1.1): a bare remount
    preserves the full /proc/mounts option set; retrans/nolease/rasize
    apply on remount; vers / echo_interval and other non-reconfigurable
    changes are rejected with -EINVAL; a remount replaying a
    server-displayed option is accepted; I/O works and dmesg is clean.

Rajasi Mandal (7):
  smb: client: sync runtime state into ctx on reconfigure
  smb: client: block non-reconfigurable option changes on remount
  smb: client: sync retrans on remount
  smb: client: block cache=ro and cache=singleclient on remount
  smb: client: apply rasize on remount
  smb: client: move struct tcon_list to cifsglob.h
  smb: client: allow nolease option to be reconfigured on remount

 fs/smb/client/cached_dir.c |  83 ++++++-
 fs/smb/client/cached_dir.h |   4 +-
 fs/smb/client/cifs_debug.c |   2 +-
 fs/smb/client/cifs_swn.h   |  14 +-
 fs/smb/client/cifsfs.c     |   6 +-
 fs/smb/client/cifsglob.h   |   7 +-
 fs/smb/client/connect.c    |   4 +-
 fs/smb/client/file.c       |   2 +-
 fs/smb/client/fs_context.c | 446 ++++++++++++++++++++++++++++++++++++-
 fs/smb/client/misc.c       |   5 -
 fs/smb/client/smb1ops.c    |   7 +-
 fs/smb/client/smb2ops.c    |   2 +-
 fs/smb/client/smb2pdu.c    |  13 +-
 fs/smb/client/trace.h      |   2 +
 14 files changed, 567 insertions(+), 30 deletions(-)


base-commit: c0a27675eaf08255017b3cabc28c99c0cd71f468
-- 
2.43.0