Pull misc vfs updates from Christian Brauner:
 "Bigger cleanups:

   - The lockref dead-count handling is tidied up.

     The open-coded check for a count below zero as the dead marker
     relies on information the caller should not have.

   - make put_mnt_ns() leave mounts connected. Destroying a mount
     namespace disconnected its mounts from their mount points. So a
     file descriptor still open on the parent of a mount point could be
     used to peek under it.

     Locked mounts were already kept connected to prevent exactly that.
     But a mount is only locked when its tree is copied across a user
     namespace boundary. So a mount namespace set up by a privileged
     component had no locked mounts and its mounts were disconnected.
     Passing UMOUNT_CONNECTED keeps every mount connected and prevents
     that bug.

   - vfs_prepare_mode() passes S_IFDIR for directories. I meant to fix
     that ago but didn't get to it. So now someone finally did it.

     This kills the exception where the mode could be 0 when a directory
     was created whereas every other creation operation passed it
     explicitly already.

   - move long delayed work for ufs, jffs2, hfsplus, hfs and affs from
     the per-cpu system_long_wq to the new unbound system_dfl_long_wq.

     None of that work relies on per-cpu state and the work item is
     enqueued with queue_delayed_work() whose timer is global anyway. So
     it may as well benefit from scheduler task placement.

  Smaller fixes and cleanups:

   - unlock_buffer() and journal_end_buffer_io_sync() use
     clear_and_wake_up_bit()

   - the pipe page pools are unified into a single per-pipe pool and the
     extra wake_up(rd_wait) is limited to EPOLLET consumers

   - eventpoll now computes its timer slack lazily in ep_poll()

   - shrink_dcache_for_umount() keeps making progress on busy roots

   - excess xarray nodes are freed in clear_inode()

   - romfs detects hard link cycles

   - the user path of nested backing files is fixed

   - pidfd holds exec_update_lock around the namespace ioctl

   - non-memcg-aware nr_cached_objects is skipped during memcg slab
     shrink

   - iomap_write_iter() always returns status

   - mangle_path() is renamed to seq_mangle_path()

   - inode timestamp accessors are annotated

   - new regression test for pipe->poll_usage.

   - a few documentation, kernel-doc and selftest fixes"

* tag 'vfs-7.3-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (67 commits)
  selftests/namespaces: Fix racy pipe handshake in timens and pidns_separate
  selftests/epoll: add a regression test for pipe->poll_usage
  pipe: only enable the extra wake_up(rd_wait) for EPOLLET consumers
  pidfd: hold exec_update_lock around namespace ioctl
  fs: fix user path of nested backing files
  fs: remove stale inode_insert5() kernel-doc parameter
  fs: fix switch/case indentation in sysfs() syscall
  fs: document semantics of kstat::{uid,gid} fields
  dcache: keep shrink_dcache_for_umount() making progress on busy roots
  seq_file: rename mangle_path to seq_mangle_path
  nstree: add/fix struct ns_id_req kernel-doc member fields
  dcache: use lockref routines for dead count checks
  lockref: tidy up dead count handling
  initramfs: fix typo in reserve_initrd_mem comment
  fs/pipe: unify the page pools into a single per-pipe pool
  fs: annotate inode timestamp accessors
  eventpoll: compute timer slack lazily in ep_poll()
  selftests/filesystems: add mntns cleanup test
  put_mnt_ns(): leave mounts connected
  affs: Move long delayed work on system_dfl_long_wq
  ...

Pull vfs lookup updates from Christian Brauner:
 "This refactors lookup_open() and adds vfs_lookup_open() for nfsd.

  mnt_want_write() and parent locking are moved into lookup_open()
  itself.

  audit_inode_child() is also now called in lookup_open() on failure.
  That is the calling convention in vfs_create() and vfs_mkdir(), but
  lookup_open() made no such call when atomic_open() should have created
  a file and did not. And neither did the regular ->create() path fwiw.

  This also contains work to remove the unneeded excl argument from the
  ->create() inode op"

* tag 'vfs-7.3-rc1.lookup' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  fs/namei.c: fix coding style in atomic_open() and lookup_open()
  fs/namei.c: fix kerneldoc of atomic_open() and vfs_lookup_open()
  fs/namei.c: update stale comments in lookup_open()
  Remove excl arg to ->create inode_operation
  fs/namei.c: update kerneldoc of atomic_open()
  vfs: call audit_inode_child() in lookup_open() on failure
  vfs: move create error && negative dentry case in lookup_open() up
  VFS: add vfs_lookup_open() for nfsd
  VFS: move delegated_inode retry loop into lookup_open()
  VFS: move mnt_want_write() and locking into lookup_open()

ceph_ioctl_set_layout() and ceph_ioctl_set_layout_policy() call
inode_owner_or_capable() with &nop_mnt_idmap instead of the idmap of the
mount the ioctl was issued on.

CephFS supports idmapped mounts (FS_ALLOW_IDMAP), so on such a mount this
compares the caller's fsuid against the unmapped on-disk owner rather than
the mapped owner: the actual owner can be wrongly denied with -EACCES and
an unrelated caller wrongly allowed.  Both functions already have the
struct file, so use file_mnt_idmap(file) instead.

Cc: stable@vger.kernel.org
Fixes: cee38bbf5556 ("ceph: add owner/capability checks for CEPH_IOC_SET_LAYOUT*")
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Reviewed-by: Xiubo Li <xiubo.li@clyso.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

CEPH_MDS_IS_READY() is parsed so that the ternary expression can
return true for an MDS entry with state 0 when it is not laggy. This
allows the random selector to choose a down/DNE rank.

Group the ternary expression under the state check so zero-state ranks
are not treated as ready.

Cc: stable@vger.kernel.org
Fixes: b38c9eb4757d ("ceph: add possible_max_rank and make the code more readable")
Link: https://tracker.ceph.com/issues/78648
Signed-off-by: Yiming Zhu <zhuyiming@kuaishou.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

The only time that 'false' is passed as the 'excl' arg to the ->create
inode_operation is in lookup_open() when ->atomic_open is not provided
by the parent directory.
*all* directory inode_operations which do not have ->atomic_open
completely ignore the 'excl' arg.

Therefore we don't need the 'excl' arg.  Those few ->create operations
which pay attention to the arg are only ever called with a value of
'true'.

We remove that arg and change all ->create operations to behave as those
thhe arg were 'true'.

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/178290671516.27465.15984496764174914338@noble.neil.brown.name
Reviewed-by: Jori Koolstra <jkoolstra@xs4all.nl>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

1. put the dead val into a macro so that it can be used in other places
2. __lockref_is_dead():
- drop the __ suffix, this is not an internal routine
- drop the spurious cast, the value is already a signed int
- use READ_ONCE to prevent any compile shenanigans
3. provide lockref_is_dead_or_zero()

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://patch.msgid.link/20260724171422.429284-2-mjguzik@gmail.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

handle_reply() stores a `ceph_mds_request` pointer in
`current->journal_info` while filling the inode and dentry cache from
an MDS reply.

An allocation in this section can enter direct reclaim and prune
dentries from another filesystem.  If this dirties an ext4 inode, ext4
starts a JBD2 transaction.  JBD2 interprets the Ceph request in
`current->journal_info` as a journal handle and dereferences the
request's `r_tid` as `h_transaction`, causing a kernel crash, e.g.:

 Unable to handle kernel paging request at virtual address 00000000077b4818
 [...]
 Internal error: Oops: 0000000096000004 [#1]  SMP
 Modules linked in:
 CPU: 6 UID: 0 PID: 2699135 Comm: kworker/6:3 Tainted: G        W           6.18.38-i3 #1113 NONE
 [...]
 Workqueue: ceph-msgr ceph_con_workfn
 pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : jbd2__journal_start+0x2c/0x208
 lr : __ext4_journal_start_sb+0x100/0x178
 [...]
 Call trace:
  jbd2__journal_start+0x2c/0x208 (P)
  __ext4_journal_start_sb+0x100/0x178
  ext4_dirty_inode+0x3c/0x90
  __mark_inode_dirty+0x58/0x400
  iput.part.0+0x2b0/0x370
  iput+0x18/0x30
  dentry_unlink_inode+0xc0/0x158
  __dentry_kill+0x80/0x250
  shrink_dentry_list+0x90/0x130
  prune_dcache_sb+0x60/0x98
  super_cache_scan+0xe8/0x190
  do_shrink_slab+0x174/0x388
  shrink_slab+0xd8/0x4c0
  shrink_node+0x31c/0x908
  do_try_to_free_pages+0xd0/0x508
  try_to_free_pages+0x11c/0x238
  __alloc_frozen_pages_noprof+0x4d0/0xdd0
  __folio_alloc_noprof+0x18/0x70
  __filemap_get_folio+0x248/0x440
  ceph_readdir_prepopulate+0x570/0x9e8
  mds_dispatch+0x1424/0x1ba0
  ceph_con_process_message+0x74/0xa0
  ceph_con_v1_try_read+0x3a0/0x1510
  ceph_con_workfn+0x260/0x460

Enter a scoped NOFS allocation context and leave it after clearing
`journal_info`.  This prevents filesystem reclaim from recursing into
another filesystem while the field contains Ceph-private data.

Cc: stable@vger.kernel.org
Fixes: 315f24088048 ("ceph: fix security xattr deadlock")
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Reviewed-by: Xiubo Li <xiubo.li@clyso.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

These permission checks were already missing in the initial
impementation of these ioctls.  This Ceph allows any user who owns a
file descriptor to manipulate the layout of any file, even if they
don't have write permissions.

It might be a good idea to guard other ioctls with permission checks
as well or even disallow regular users (even if they own the file) to
manipulate layout settings completely, as this may be abused to DoS
the Ceph servers, but right now, I find it most urgent to have setter
checks at all.

Cc: stable@vger.kernel.org
Fixes: 8f4e91dee2a2 ("ceph: ioctls")
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Xiubo Li <xiubo.li@clyso.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

A reader can hang forever in __ceph_get_caps() when the client no
longer holds `FILE_RD`, but local cap state still says that the
capability is already wanted (via `mds_wanted`).

One way to trigger this is through MDS cap revocation.  If another
client performs a conflicting operation, the MDS can revoke `FILE_RD`
from the reader; the next read then has to reacquire `FILE_RD`.  If
the cap update that should request `FILE_RD` never reaches the MDS
after `cap->mds_wanted` was raised, the reader is left holding only
non-file caps while local `mds_wanted` still includes the file read
caps.

In that state, try_get_cap_refs() sees `need <= mds_wanted` and
returns 0, so __ceph_get_caps() just waits on `i_cap_wq`.  If the cap
update that was supposed to request `FILE_RD never reaches the MDS
after `cap->mds_wanted was` raised, no further request is sent and the
waiter can sleep indefinitely until unrelated cap traffic happens to
wake it up.

The ordering issue is that `cap->mds_wanted` is updated in
__prep_cap() before the `CEPH_MSG_CLIENT_CAPS message` is actually
queued for send.  That makes one field serve two different meanings at
once: what this client wants, and what the client believes the MDS
already knows it wants.

A proper fix would be to split those states and track whether a cap
update is actually in flight or has been observed by the MDS.
However, simply moving the `cap->mds_wanted assignment` later would
not be sufficient: queueing the message in the messenger does not
guarantee that the MDS processed that specific wanted set, and
reconnect or message loss can still invalidate that assumption.
Fixing that properly would require a larger rework of the cap state
machine.

To allow simpler backports to stable kernels, this patch implements a
simpler workaround:

- stop waiting forever in __ceph_get_caps(); after a bounded wait,
  fall back to the renew path

- make ceph_renew_caps() issue a synchronous `OPEN` request whenever
  the inode still does not actually hold the wanted caps, instead of
  only calling ceph_check_caps()

The extra issued-vs-wanted check in ceph_renew_caps() is necessary
because the previous test only checked whether the inode still had any
real caps at all.  That is not enough after revocation: the client can
still hold something like `pLs` and yet be missing `FILE_RD`
completely.  In that case, falling back to ceph_check_caps() is not
sufficient, because it still trusts `cap->mds_wanted` and may resend
nothing.  By requiring `(issued & wanted) == wanted` before taking the
asynchronous path, the code only uses ceph_check_caps() when the
`wanted caps` are already actually issued.  Otherwise, it sends the
synchronous `OPEN` renew.

This preserves the existing asynchronous fast path when the wanted
caps are already issued, avoids changing cap-state semantics, and
fixes the hang by guaranteeing that a stalled waiter eventually
retries through a path that does not rely on the stale `mds_wanted`
state.

[ idryomov: move CEPH_GET_CAPS_WAIT_TIMEOUT from libceph.h to
  mds_client.h, formatting ]

Cc: stable@vger.kernel.org
Fixes: 0a454bdd501a ("ceph: reorganize __send_cap for less spinlock abuse")
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

The ceph_readdir() function allocates a ceph_mds_request via
ceph_mdsc_create_request() and stores it in dfi->last_readdir. In
the directory entry processing loop, if the entry's offset is less
than ctx->pos or if the inode pointer is unexpectedly NULL, the
function returns -EIO without releasing the reference held by
dfi->last_readdir, causing a refcount leak.

Fix this by adding ceph_mdsc_put_request(dfi->last_readdir) before
returning on these error paths. Also set dfi->last_readdir to NULL
for safety, matching the cleanup done at the normal exit.

Cc: stable@vger.kernel.org
Fixes: af9ffa6df7e3 ("ceph: add support to readdir for encrypted names")
Signed-off-by: WenTao Liang <vulab@iscas.ac.cn>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>