Pull more MM updates from Andrew Morton:

 - "mm/rmap: index MAP_PRIVATE file-backed folios by anonymous pgoff"
   (Lorenzo Stoakes)

   Index MAP_PRIVATE file-backed folios by their anonymous page offset
   to resolve confusion around reverse mapping for zeroed and CoW'd
   file-backed memory.

   Use this new VMA anonymous page offset tracking to eliminate index
   conflicts and lay the foundation for scalable CoW performance
   improvements.

 - "promote mapped executable folios after first usage for MGLRU"
   (Baolin Wang)

   Make MGLRU's protection of mapped executable file folios more
   reliable. Follow the classical LRU's logic, promoting mapped
   executable file folios after their first usage to give executable
   code a better chance to stay in memory and improve workload
   performance.

 - "mm: vmscan: fix node reclaim ignoring swappiness parameter" (Ridong
   Chen)

   Fix per-node proactive reclaim interface's ignoring the swappiness
   parameter when CONFIG_MEMCG is disabled by consolidating
   sc_swappiness() into a single function that checks
   proactive_swappiness regardless of kernel configuration.

 - "mm/vmscan: reduce lru_lock contention via vmstat-derived
   scan-balance cost" (Usama Arif)

   Reduce lru_lock contention in the reclaim path by deriving
   scan-balance costs from vmstat counters rather than lock-acquired
   producer updates.

   Read and decay these cost signals on the reclaim side under a
   dedicated per-lruvec lock, reducing total LRU lock wait time by over
   60% without impacting scan throughput.

 - "zram: fix zram issues reported by sashiko" (Sergey Senozhatsky)

   Fix two low-risk zram bugs which Sashiko spotted in drive-by review.

 - "Honor XA_FLAGS_ACCOUNT in xas_split_alloc() and charge to folio's
   memcg" (Zi Yan)

   Fix xas_split_alloc() by enabling target folio memcg charging during
   splits and adding the missing __GFP_ACCOUNT flag for proper XArray
   node memory accounting.

 - "selftests/mm: use pattern matching in .gitignore" (Pratyush Mallick)

   Replace hardcoded binary names in selftests/mm/.gitignore with a
   generic pattern-matching rule to automatically ignore generated test
   files and avoid manual updates when adding new tests.

 - "mm/page_ext: remove pgdat_page_ext_init()" (Sang-Heon Jeon)

   Make the incompatibility between FLATMEM and NUMA explicit in
   mm/Kconfig and remove the unused pgdat_page_ext_init() function.

 - "zram: fix zstd error paths and add parameter validation" (Haoqin
   Huang)

   Clean up zram compression backends by removing redundant error
   cleanup, adding parameter and dictionary validation, auto-prefixing
   algorithm error logs, and resetting parameters prior to
   reinitialization.

 - "zram: fix stale scan bounds after reinitialization" (Longlong Xia)

   Prevent out-of-bounds slot accesses during concurrent zram resets by
   moving table scan bound calculations under dev_lock in
   writeback_store() and read_block_state().

 - "add anon mTHP collapse test cases" (Baolin Wang)

   Extend selftests helper functions to support arbitrary page orders
   and add new test cases and options for mTHP collapse in khugepaged.

 - "selftests/mm: Handle unsupported and transient test conditions"
   (Muhammad Usama Anjum)

   Update MM selftests to report a SKIP status instead of a failure when
   required kernel or filesystem features are unsupported, while adding
   retry logic for transient page migration errors.

 - "mm/zswap: Fixes and improves the zswap shrink" (Hao Jia)

   Fix the missing zswap global shrinker when CONFIG_MEMCG is disabled
   and extend shrink_memcg() to support batch writeback for improved
   writeback efficiency.

 - "alloc_tag: introduce IOCTL-based filtering for MAP" (Suren
   Baghdasaryan)

   Introduce an IOCTL-based binary interface for memory allocation
   profiling that enables kernel-side filtering before per-CPU counter
   aggregation.

   This eliminates the text-parsing overhead of /proc/allocinfo and
   provides up to a 20x speedup by transferring only filtered allocation
   data to userspace.

 - "better block swap batching and a different take on swap_ops v5"
   (Christoph Hellwig)

   Refactor block swap I/O to use swap_iocb for batching instead of
   single-bio requests and rebase the swap_ops interface, achieving
   faster swap throughput during kernel builds.

 - "mm: kmemleak: reduce transient false positives by confirming leaks"
   (Catalin Marinas)

   Reduce false-positive kmemleak reports by combining two kmemleak
   enhancements that add a second confirmation scan and a configurable
   minimum unreferenced scan count module parameter.

 - "mm: kmemleak: default min_unref_scans to 2 for verbose kernels"
   (Breno Leitao)

   Auto-scanning kernels can generate false-positive memory leak reports
   on single scans, so this patch defaults min_unref_scans to 2 when
   CONFIG_DEBUG_KMEMLEAK_VERBOSE is enabled to require a second
   confirming scan.

 - "swap_ops updates" (Christoph Hellwig)

   Batching I/O for synchronous swap devices causes performance
   regressions and filesystem-based swap suffers from double-indirection
   overhead. This series resolves both issues by reintroducing per-folio
   writes for synchronous swap and allowing filesystems to directly
   export their own swap_ops.

 - "mm/khugepaged: several cleanups" (Nico Pache)

   khugepaged accumulated redundant state-checking patterns and outdated
   comments following mTHP integration. Introduce dedicated helpers for
   PTE validation and event counting while refreshing the internal
   documentation.

 - "maple_tree: lock checking and clean ups" (Liam Howlett)

   Syzbot reports incorrectly blame memory management exit paths for
   locking bugs, maple tree erase operations risk allocation failures
   without gfp flags and internal documentation lacks clarity.

   Improve lock error detection, update docs, fix race and allocation
   edge cases and optimize erase allocations using a fallback to
   GFP_KERNEL | GFP_NOFAIL.

* tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (172 commits)
  selftests/proc: make proc-maps-race work with READ_IMPLIES_EXEC
  memcg: move LRU size accounting on reparenting instead of copying it
  mm/vmscan: fix comment logic in balance_pgdat
  maple_tree: add helper mas_make_walkable()
  maple_tree: avoid extra gap calculation
  maple_tree: fix argument name in header
  maple_tree: change two GFP flags in tests
  maple_tree: document erase and allocations better
  maple_tree: avoid mas_erase() and mtree_erase() failures
  maple_tree: document that erase may use GFP_KERNEL for allocations
  maple_tree: catch race in mas_alloc_cyclic()
  maple_tree: add bulk parent set helper
  maple_tree: micro optimisation of mas_wr_store_type()
  maple_tree: optimise mas_wr_node_store() when not in rcu mode
  maple_tree: use prefetched value in mas_wr_store_type()
  maple_tree: clarify comments on mas_nomem()
  maple_tree: drop MAPLE_ALLOC_SLOTS
  maple_tree: drop dead code from mas_extend_spanning_null()
  maple_tree: documentation fix
  maple_tree: add write lock checking with lockdep sequence numbers
  ...

Currently swap to and from file systems goes through two indirect calls
between the swap ops and the swap_rw method.  Reduce this by directly
providing the swap_ops from the file system.

For this refactor swap_fs_submit into a swap_fs_prepare_rw helper that
initializes the iov_iter on the callers stack so that file systems can
call it directly, and use that to initialize file system specific ops in
the NFS and SMB clients, which then get passed to swap_fs_activate.

Link: https://lore.kernel.org/20260723054622.3460249-4-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Pull ext4 updates from Ted Ts'o:

 - Improve performance by allowing parallel DIO writes when we were
   previously being overly conservative when checking whether it was
   safe to avoid requiring an exclusive lock

 - Improve the performance of ext4_mb_prefetch() used by fallocate() by
   avoiding work when it is not needed

 - Remove the unnecessary custom end_io function
   ext4_end_buffer_io_sync()

 - Improve performance when performing an overwrite to an already
   uptodate folio

 - Clean up how we handle deallocating EA inodes to avoid a potential
   lock ordering issue when there is a failed mount while an EA inode is
   still being evicted

 - Use str_plural() instead of a custom macro

 - Avoid soft lockups or RCU stalls if there are many busy buffers
   (caused by heavy I/O) while checkpointing

 - Use scoped NOFS when starting a handle in nojournal mode

 - Align fields in handle structure to optimize setting and getting the
   h_type and h_line_no fields

 - Fix documentation of the meta_bg block group layout

 - Bug fixes:
    - Fix a potential out-of-bounds read in ext4_read_inline_dir()
    - Fix a potential deadlock when concurrent xattr operations are
      racing with each other when some of the xattrs are using the
      ea_inode feature
    - Fix a spurious warning with data=journal that can be triggered
      when writeback races with remounting the file system read-only
    - Fix a potential deadlock when EXT4_IOC_MIGRATE races with a file
      system freeze operation
    - Make sure all in-flight direct I/O operations are complete before
      falling back to buffered I/O
    - Handle IOCB_NOWAIT properly when performing a extending DAX write
    - Prevent potentially sleeping on a block allocation when
      IOCB_NOWAIT is set
    - Fix potential races when racing an inline data write with a page
      fault
    - Propagate errors when adding or removing extent ranges during a
      fast commit replay
    - Avoid trying to expand an inode's extra size when it is being
      evicted to avoid a number of corner case or deadlocks
    - Avoid spurious error when retrying inode extra size expansion
    - Fix corner cases where we underestimate the number of journal
      credits needed
    - Avoid hangs/crashes/WARNINGS caused by maliciously corrupted file
      systems
    - Don't issue spurious orphan clean message on RO file systems
    - Avoid leaving the file system in an inconsistent state after a
      crash when a WRITE_ZEROS in progress converting an unwritten
      extent to a written extent
    - Handle WRITE_ZEROS correctly when there are some partially dirtied
      regions in the page cache
    - Pass errors during zero-rage, truncate, or punch hole to the
      caller if ext4_get_block() fails
    - Wait for writeback to finish when triggered by zero-range or
      zero-range for those devices that require stable writes
    - If the reserved gid superblock field is set, set the reserved gid
      instead of the reserved uid

* tag 'ext4_for_linus-7.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (56 commits)
  ext4: fix estimate extent index blocks in ext4_ext_index_trans_blocks()
  ext4: fix transaction overflow during writeback
  ext4: teach ext4_meta_trans_blocks() about number of allocated extents
  ext4: guard against NULL s_group_info in ext4_get_group_info
  ext4: fix spurious message about orphan cleanup on RO fs
  ext4: stop retrying saturated xattr cache entries
  ext4: don't enable DAX on new encrypted files
  ext4: protect WRITE_ZEROES written extents with orphan list
  ext4: export converted block count from ext4_convert_unwritten_extents()
  ext4: fix incorrect function call when initializing s_resgid
  ext4: validate EA inode i_nlink in ext4_xattr_inode_iget
  jbd2: align h_type and h_line_no in the handle structure on byte boundaries
  ext4: enable scoped NOFS when starting a handle in nojournal mode
  ext4: write back partial-zeroed edges in WRITE_ZEROES
  ext4: zero out whole block for clean edges in WRITE_ZEROES
  ext4: track partial-zero outcome per edge in ext4_zero_partial_blocks()
  ext4: clarify return semantics of ext4_load_tail_bh()
  ext4: move partial block zeroing earlier in ext4_zero_range()
  ext4: check return value of ext4_get_block() in ext4_load_tail_bh()
  ext4: skip tail block zeroing for inline data files
  ...

Pull vfs writeback updates from Christian Brauner:
 "This makes sync_inode_metadata() and writeback_single_inode() persist
  not only the inode but all metadata associated with it.

  A new .sync_inode_metadata superblock operation is called from
  __writeback_single_inode(). Alongside it a new I_METADATA_WRITEBACK
  state flag is added.

  Filesystems no longer need their own mmb_fsync() implementations and
  can just use simple_fsync(). All metadata is now written for IS_SYNC
  and IS_DIRSYNC inodes. Races where several fsyncs raced and mmb_sync()
  could return before all buffers were really persisted are fixed since
  I_SYNC now serializes properly.

  The I_METADATA_WRITEBACK scheme also fixes the case where a
  WB_SYNC_NONE writeback landing between write(2) and fsync(2) left
  fsync(2) failing to persist the inode. That problem is not specific to
  filesystems using the generic metadata bh tracking, and the ones that
  do not are left alone.

  ext2, udf, bfs, minix, fat and ext4 in nojournal mode have their data
  integrity writeout fixed and are converted. affs drops metadata bh
  tracking and mmb_fsync() is removed.

  A few other fixes came out of this:

   - a UAF in mark_buffer_write_io_error()

   - missed inode writeback when racing with __writeback_single_inode()

   - ext4 allocating the mapping_metadata_bhs struct on demand

   - three fat fixes: a lost inode update in do_msdos_rename() with
     DIRSYNC, inode buffer write errors not propagating out of
     fat_sync_inode_metadata() and directory entries not being
     persisted on fsync(2) of the root directory"

* tag 'vfs-7.3-rc1.sync' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (24 commits)
  writeback: Export __inode_attach_wb()
  fat: Fix persisting directory entries on fsync(2) of the root directory
  fat: Propagate inode buffer write errors from fat_sync_inode_metadata()
  fat: Fix lost inode update in do_msdos_rename() with DIRSYNC
  vfs: Remove mmb_fsync()
  fat: Replace fat_sync_inode() with sync_inode_metadata()
  fat: Fix missed inode writeback during fsync(2)
  ext4: Fix data integrity writeout issues in nojournal mode
  minix: Fix data integrity writeout issues
  bfs: Fix data integrity writeout issues
  udf: Fold udf_update_inode() into udf_write_inode()
  udf: Use sync_inode_metadata() in udf_evict_inode()
  udf: Drop udf_sync_inode()
  udf: Use sync_inode_metadata() to writeout IS_SYNC inode
  udf: Fix data integrity writeout issues
  ext2: Fix data integrity writeout issues
  ext2: Avoid unnecessary inode buffer writeback for sync(2)
  ext2: Drop __ext2_write_inode()
  ext2: Fix lost inode updates for IS_SYNC inodes
  fs: Provide way for filesystem to wait for metadata writeback
  ...

Pull vfs superblock updates from Christian Brauner:

 - Make it possible to share a block device between multiple
   filesystems.

   erofs can mount read-only blob devices shared between many
   superblocks, but because we only tracked a single superblock a
   freeze, thaw, removal or sync on such a device was never propagated
   to all the superblocks using it, and there was no way to find them.

   Add an efficient table to lookup all superblocks using a given block
   device.

 - A bunch of pre-existing fixes fell out of this work:

   A block-device freeze racing a btrfs device change could leave the
   whole filesystem stuck frozen. A bdev_freeze() issued by "dmsetup
   suspend" or an LVM snapshot resolves that holder to freeze the
   filesystem. and bdev_thaw() resolves it again to thaw. A freeze
   landing while btrfs is adding, removing or replacing a device freezes
   the filesystem. The membership change then drops that link. So the
   matching thaw could no longer find the superblock.

   Forbid freezing a device for the duration of a membership change,
   modelled on deny_write_access()/allow_write_access().

* tag 'vfs-7.3-rc1.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (24 commits)
  super: fix dying superblock warning messages
  block: reject block device inodes with i_rdev == 0 in lookup_bdev()
  selftests/filesystems: add ustat() coverage
  fs: look up the superblock via the device table in user_get_super()
  super: make fs_holder_ops private
  f2fs: open via dedicated fs bdev helpers
  erofs: open via dedicated fs bdev helpers
  fs: tolerate per-superblock freeze errors on shared devices
  fs: look up superblocks via the device table in fs_holder_ops
  ext4: open via dedicated fs bdev helpers
  btrfs: open via dedicated fs bdev helpers
  xfs: port to fs_bdev_file_open_by_path()
  fs: add dedicated block device open helpers for filesystems
  fs: maintain a global device-to-superblock table
  ocfs2: don't reset s_dev on dismount
  ext4: use anonymous devices for KUnit test superblocks
  fs, block: move blk_mode_t and fop_flags_t into <linux/types.h>
  super: take lock after last reference count
  super: convert s_count to refcount_t s_passive
  btrfs: deny freezing devices undergoing a replace
  ...

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()

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>

syzbot reported a KCSAN race between fill_mg_cmtime() and
inode_set_ctime_to_ts() on inode->i_ctime_{sec,nsec}.

stat/getattr can sample inode timestamps while update paths store new
values concurrently, so KCSAN can report benign races on these fields.

Annotate the timestamp accessors with READ_ONCE()/WRITE_ONCE(), and use
the ctime accessor for the remaining ctime loads.  This avoids the KCSAN
reports without changing timestamp semantics.

Fixes: 4e40eff0b573 ("fs: add infrastructure for multigrain timestamps")
Reported-by: syzbot+8b3bd9f8a06658479d4a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8b3bd9f8a06658479d4a
Signed-off-by: Yu Peng <pengyu@kylinos.cn>
Link: https://patch.msgid.link/20260708080232.2564807-1-pengyu@kylinos.cn
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Currently, inode and in general metadata writeback is handled in a lazy
manner. When inode is dirty, __writeback_single_inode() calls
.write_inode method which for lots of filesystems just copies inode
metadata into the underlying block buffer. Writeback of other metadata
associated with the inode (as well as buffers underlying inodes) is
usually handled completely separately and implicitely during writeback
of block device inode. This is good for efficiency of WB_SYNC_NONE
writeback or sync(2). However it becomes problematic for situations
where we want to make sure inode and its metadata is really persistent
on disk. fsync(2) is the most pronounced example of this and thus we
have grown a special file operation and various helper functions to
assist with this task. However fsync(2) is not the only case, For
example directories with DIRSYNC flag need similar functionality and
current use of sync_inode_metadata() for this task in filesystems
generally misses writeout of necessary metadata.

Furthermore even fsync(2) handling as implemented by simple_fsync() or
similar helpers is racy and can fail to properly persist the inode. The
problem is that WB_SYNC_NONE writeback can copy inode metadata into
underlying buffer and clean inode dirty bits. Following fsync(2) will
see inode is clean and will fail to make sure underlying buffer is
written out.

When multiple fsync(2) calls race, there's also another type of race
involving mmb_fsync(). There the problem is buffers already submitted to
the disk are no longer tracked in the mmb list and so racing mmb_sync()
can return before all of the IO completes.

Provide a new inode state bit I_METADATA_WRITEBACK tracking whether
writeback of inode related metadata may be needed for successful data
integrity sync and if this bit is set __writeback_single_inode() for
data integrity writeback will call new superblock operation
.sync_inode_metadata whose task is to make sure all metadata associated
with the inode (including the inode itself) is properly persisted. This
will allow filesystems to address the data integrity issues described
above and at the same time somewhat simplify our fsync implementations.
Issues with racing fsync(2) calls will be addressed by synchronization on
I_SYNC inode state which is set while calling .sync_inode_metadata, issues
with missed inode buffer writeback are fixed by filesystems looking up
corresponding buffer head and writing it out if needed.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260727104923.3828017-25-jack@suse.cz
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>