When iterating the chunk maps when a device replace finishes we are doing
a full rbtree search for each chunk map, which is not the most efficient
thing to do, wasting CPU time. As we are holding a write lock on the tree
during the whole iteration, we can simply start from the first node in the
tree and then move to the next chunk map by doing a rb_next() call - the
only exception is when we need to reschedule, in which case we have to do
a full rbtree search since we dropped the write lock and the tree may have
changed (chunk maps may have been removed and the tree got rebalanced).
So just do that.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

At the end of a device replace we must go over all the chunk maps and
update their stripes to point to the target device instead of the source
device. We iterate over the chunk maps while holding a write lock and
we never reschedule, which can result in monopolizing a CPU for too long
and blocking readers for too long (it's a rw lock, non-blocking).

So improve on this by rescheduling if necessary. This is safe because at
this point we are holding the chunk mutex, which means no new chunks can
be allocated and therefore we don't risk missing a new chunk map that
covers a range behind the last one we processed before rescheduling.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

The range is specified only in two ways, we can simplify the case for
the whole filesystem range as a NULL block group parameter.

Signed-off-by: David Sterba <dsterba@suse.com>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull btrfs updates from David Sterba:
 "Mostly stabilization, refactoring and cleanup changes. There rest are
  minor performance optimizations due to caching or lock contention
  reduction and a few notable fixes.

  Performance improvements:

   - minor speedup in logging when repeatedly allocated structure is
     preallocated only once, improves latency and decreases lock
     contention

   - minor throughput increase (+6%), reduced lock contention after
     clearing delayed allocation bits, applies to several common
     workload types

   - skip full quota rescan if a new relation is added in the same
     transaction

  Fixes:

   - zstd fix for inline compressed file in subpage mode, updated
     version from the 6.8 time

   - proper qgroup inheritance ioctl parameter validation

   - more fiemap followup fixes after reduced locking done in 6.8:
      - fix race when detecting delalloc ranges

  Core changes:

   - more debugging code:
      - added assertions for a very rare crash in raid56 calculation
      - tree-checker dumps page state to give more insights into
        possible reference counting issues

   - add checksum calculation offloading sysfs knob, for now enabled
     under DEBUG only to determine a good heuristic for deciding the
     offload or synchronous, depends on various factors (block group
     profile, device speed) and is not as clear as initially thought
     (checksum type)

   - error handling improvements, added assertions

   - more page to folio conversion (defrag, truncate), cached size and
     shift

   - preparation for more fine grained locking of sectors in subpage
     mode

   - cleanups and refactoring:
      - include cleanups, forward declarations
      - pointer-to-structure helpers
      - redundant argument removals
      - removed unused code
      - slab cache updates, last use of SLAB_MEM_SPREAD removed"

* tag 'for-6.9-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (114 commits)
  btrfs: reuse cloned extent buffer during fiemap to avoid re-allocations
  btrfs: fix race when detecting delalloc ranges during fiemap
  btrfs: fix off-by-one chunk length calculation at contains_pending_extent()
  btrfs: qgroup: allow quick inherit if snapshot is created and added to the same parent
  btrfs: qgroup: validate btrfs_qgroup_inherit parameter
  btrfs: include device major and minor numbers in the device scan notice
  btrfs: mark btrfs_put_caching_control() static
  btrfs: remove SLAB_MEM_SPREAD flag use
  btrfs: qgroup: always free reserved space for extent records
  btrfs: tree-checker: dump the page status if hit something wrong
  btrfs: compression: remove dead comments in btrfs_compress_heuristic()
  btrfs: subpage: make writer lock utilize bitmap
  btrfs: subpage: make reader lock utilize bitmap
  btrfs: unexport btrfs_subpage_start_writer() and btrfs_subpage_end_and_test_writer()
  btrfs: pass a valid extent map cache pointer to __get_extent_map()
  btrfs: merge btrfs_del_delalloc_inode() helpers
  btrfs: pass btrfs_device to btrfs_scratch_superblocks()
  btrfs: handle transaction commit errors in flush_reservations()
  btrfs: use KMEM_CACHE() to create btrfs_free_space cache
  btrfs: use KMEM_CACHE() to create delayed ref caches
  ...

Pull block handle updates from Christian Brauner:
 "Last cycle we changed opening of block devices, and opening a block
  device would return a bdev_handle. This allowed us to implement
  support for restricting and forbidding writes to mounted block
  devices. It was accompanied by converting and adding helpers to
  operate on bdev_handles instead of plain block devices.

  That was already a good step forward but ultimately it isn't necessary
  to have special purpose helpers for opening block devices internally
  that return a bdev_handle.

  Fundamentally, opening a block device internally should just be
  equivalent to opening files. So now all internal opens of block
  devices return files just as a userspace open would. Instead of
  introducing a separate indirection into bdev_open_by_*() via struct
  bdev_handle bdev_file_open_by_*() is made to just return a struct
  file. Opening and closing a block device just becomes equivalent to
  opening and closing a file.

  This all works well because internally we already have a pseudo fs for
  block devices and so opening block devices is simple. There's a few
  places where we needed to be careful such as during boot when the
  kernel is supposed to mount the rootfs directly without init doing it.
  Here we need to take care to ensure that we flush out any asynchronous
  file close. That's what we already do for opening, unpacking, and
  closing the initramfs. So nothing new here.

  The equivalence of opening and closing block devices to regular files
  is a win in and of itself. But it also has various other advantages.
  We can remove struct bdev_handle completely. Various low-level helpers
  are now private to the block layer. Other helpers were simply
  removable completely.

  A follow-up series that is already reviewed build on this and makes it
  possible to remove bdev->bd_inode and allows various clean ups of the
  buffer head code as well. All places where we stashed a bdev_handle
  now just stash a file and use simple accessors to get to the actual
  block device which was already the case for bdev_handle"

* tag 'vfs-6.9.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (35 commits)
  block: remove bdev_handle completely
  block: don't rely on BLK_OPEN_RESTRICT_WRITES when yielding write access
  bdev: remove bdev pointer from struct bdev_handle
  bdev: make struct bdev_handle private to the block layer
  bdev: make bdev_{release, open_by_dev}() private to block layer
  bdev: remove bdev_open_by_path()
  reiserfs: port block device access to file
  ocfs2: port block device access to file
  nfs: port block device access to files
  jfs: port block device access to file
  f2fs: port block device access to files
  ext4: port block device access to file
  erofs: port device access to file
  btrfs: port device access to file
  bcachefs: port block device access to file
  target: port block device access to file
  s390: port block device access to file
  nvme: port block device access to file
  block2mtd: port device access to files
  bcache: port block device access to files
  ...

Replace the two parameters bdev and name by one that can be used to get
them both.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

With help of neovim, LSP and clangd we can identify header files that
are not actually needed to be included in the .c files. This is focused
only on removal (with minor fixups), further cleanups are possible but
will require doing the header files properly with forward declarations,
minimized includes and include-what-you-use care.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Link: https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-19-adbd023e19cc@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

There's a syzbot report that device name buffers passed to device
replace are not properly checked for string termination which could lead
to a read out of bounds in getname_kernel().

Add a helper that validates both source and target device name buffers.
For devid as the source initialize the buffer to empty string in case
something tries to read it later.

This was originally analyzed and fixed in a different way by Edward Adam
Davis (see links).

Link: https://lore.kernel.org/linux-btrfs/000000000000d1a1d1060cc9c5e7@google.com/
Link: https://lore.kernel.org/linux-btrfs/tencent_44CA0665C9836EF9EEC80CB9E7E206DF5206@qq.com/
CC: stable@vger.kernel.org # 4.19+
CC: Edward Adam Davis <eadavis@qq.com>
Reported-and-tested-by: syzbot+33f23b49ac24f986c9e8@syzkaller.appspotmail.com
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>