When a writer thread executes a chain of log intent items, the AG header
buffer locks will cycle during a transaction roll to get from one intent
item to the next in a chain.  Although scrub takes all AG header buffer
locks, this isn't sufficient to guard against scrub checking an AG while
that writer thread is in the middle of finishing a chain because there's
no higher level locking primitive guarding allocation groups.

When there's a collision, cross-referencing between data structures
(e.g. rmapbt and refcountbt) yields false corruption events; if repair
is running, this results in incorrect repairs, which is catastrophic.

Fix this by adding to the perag structure the count of active intents
and make scrub wait until it has both AG header buffer locks and the
intent counter reaches zero.

One quirk of the drain code is that deferred bmap updates also bump and
drop the intent counter.  A fundamental decision made during the design
phase of the reverse mapping feature is that updates to the rmapbt
records are always made by the same code that updates the primary
metadata.  In other words, callers of bmapi functions expect that the
bmapi functions will queue deferred rmap updates.

Some parts of the reflink code queue deferred refcount (CUI) and bmap
(BUI) updates in the same head transaction, but the deferred work
manager completely finishes the CUI before the BUI work is started.  As
a result, the CUI drops the intent count long before the deferred rmap
(RUI) update even has a chance to bump the intent count.  The only way
to keep the intent count elevated between the CUI and RUI is for the BUI
to bump the counter until the RUI has been created.

A second quirk of the intent drain code is that deferred work items must
increment the intent counter as soon as the work item is added to the
transaction.  When a BUI completes and queues an RUI, the RUI must
increment the counter before the BUI decrements it.  The only way to
accomplish this is to require that the counter be bumped as soon as the
deferred work item is created in memory.

In the next patches we'll improve on this facility, but this patch
provides the basic functionality.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Add a new tracepoint so that I can see exactly what and where we failed
the refcount check.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Update the copyright years in the scrub/ source code files.  This isn't
required, but it's helpful to remind myself just how long it's taken to
develop this feature.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Fix the spdx tags to match current practice, and update the author
contact information.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

There are a few places in the XFS codebase where a caller has either an
active or a passive reference to a perag structure and wants to give
a passive reference to some other piece of code.  Btree cursor creation
and inode walks are good examples of this.  Replace the open-coded logic
with a helper to do this.

The new function adds a few safeguards -- it checks that there's at
least one reference to the perag structure passed in, and it records the
refcount bump in the ftrace information.  This makes it much easier to
debug perag refcounting problems.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Give the xfs_refcount_intent a passive reference to the perag structure
data.  This reference will be used to enable scrub intent draining
functionality in subsequent patches.  Any space being modified by a
refcount intent is already allocated, so we need to be able to operate
even if the AG is being shrunk or offlined.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Give the xfs_rmap_intent a passive reference to the perag structure
data.  This reference will be used to enable scrub intent draining
functionality in subsequent patches.  The space we're (reverse) mapping
is already allocated, so we need to be able to operate even if the AG is
being shrunk or offlined.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Give the xfs_extfree_intent an passive reference to the perag structure
data.  This reference will be used to enable scrub intent draining
functionality in subsequent patches.  The space being freed must already
be allocated, so we need to able to run even if the AG is being offlined
or shrunk.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Pass a reference to the per-AG structure to xfs_free_extent.  Most
callers already have one, so we can eliminate unnecessary lookups.  The
one exception to this is the EFI code, which the next patch will fix.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Give the xfs_bmap_intent an active reference to the perag structure
data.  This reference will be used to enable scrub intent draining
functionality in subsequent patches.  Later, shrink will use these
passive references to know if an AG is quiesced or not.

The reason why we take a passive ref for a file mapping operation is
simple: we're committing to some sort of action involving space in an
AG, so we want to indicate our interest in that AG.  The space is
already allocated, so we need to be able to operate on AGs that are
offline or being shrunk.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Add the seventh and final chapter of the online fsck documentation,
where we talk about future functionality that can tie in with the
functionality provided by the online fsck patchset.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Add the sixth chapter of the online fsck design documentation, where
we discuss the details of the data structures and algorithms used by the
driver program xfs_scrub.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Directory tree repairs are the least complete part of online fsck, due
to the lack of directory parent pointers.  However, even without that
feature, we can still make some corrections to the directory tree -- we
can salvage as many directory entries as we can from a damaged
directory, and we can reattach orphaned inodes to the lost+found, just
as xfs_repair does now.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

File-based metadata (such as xattrs and directories) can be extremely
large.  To reduce the memory requirements and maximize code reuse, it is
very convenient to create a temporary file, use the regular dir/attr
code to store salvaged information, and then atomically swap the extents
between the file being repaired and the temporary file.  Record the high
level concepts behind how temporary files and atomic content swapping
should work, and then present some case studies of what the actual
repair functions do.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Certain parts of the online fsck code need to scan every file in the
entire filesystem.  It is not acceptable to block the entire filesystem
while this happens, which means that we need to be clever in allowing
scans to coordinate with ongoing filesystem updates.  We also need to
hook the filesystem so that regular updates propagate to the staging
records.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Add to the fifth chapter of the online fsck design documentation, where
we discuss the details of the data structures and algorithms used by the
kernel to repair file metadata.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Add a discussion of the btree bulk loading code, which makes it easy to
take an in-memory recordset and write it out to disk in an efficient
manner.  This also enables atomic switchover from the old to the new
structure with minimal potential for leaking the old blocks.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Add a discussion of pageable kernel memory, since online fsck needs
quite a bit more memory than most other parts of the filesystem to stage
records and other information.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Writes to an XFS filesystem employ an eventual consistency update model
to break up complex multistep metadata updates into small chained
transactions.  This is generally good for performance and scalability
because XFS doesn't need to prepare for enormous transactions, but it
also means that online fsck must be careful not to attempt a fsck action
unless it can be shown that there are no other threads processing a
transaction chain.  This part of the design documentation covers the
thinking behind the consistency model and how scrub deals with it.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Begin the fifth chapter of the online fsck design documentation, where
we discuss the details of the data structures and algorithms used by the
kernel to examine filesystem metadata and cross-reference it around the
filesystem.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Start the fourth chapter of the online fsck design documentation, which
discusses the user interface and the background scrubbing service.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Start the third chapter of the online fsck design documentation.  This
covers the testing plan to make sure that both online and offline fsck
can detect arbitrary problems and correct them without making things
worse.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Start the second chapter of the online fsck design documentation.
This covers the general theory underlying how online fsck works.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Start the first chapter of the online fsck design documentation.
This covers the motivations for creating this in the first place.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Pull perf fixes from Borislav Petkov:

 - Fix "same task" check when redirecting event output

 - Do not wait unconditionally for RCU on the event migration path if
   there are no events to migrate

* tag 'perf_urgent_for_v6.3_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Fix the same task check in perf_event_set_output
  perf: Optimize perf_pmu_migrate_context()

Pull x86 fixes from Borislav Petkov:

 - Add a new Intel Arrow Lake CPU model number

 - Fix a confusion about how to check the version of the ACPI spec which
   supports a "online capable" bit in the MADT table which lead to a
   bunch of boot breakages with Zen1 systems and VMs

* tag 'x86_urgent_for_v6.3_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpu: Add model number for Intel Arrow Lake processor
  x86/acpi/boot: Correct acpi_is_processor_usable() check
  x86/ACPI/boot: Use FADT version to check support for online capable

Pull compute express link (cxl) fixes from Dan Williams:
 "Several fixes for driver startup regressions that landed during the
  merge window as well as some older bugs.

  The regressions were due to a lack of testing with what the CXL
  specification calls Restricted CXL Host (RCH) topologies compared to
  the testing with Virtual Host (VH) CXL topologies. A VH topology is
  typical PCIe while RCH topologies map CXL endpoints as Root Complex
  Integrated endpoints. The impact is some driver crashes on startup.

  This merge window also added compatibility for range registers (the
  mechanism that CXL 1.1 defined for mapping memory) to treat them like
  HDM decoders (the mechanism that CXL 2.0 defined for mapping
  Host-managed Device Memory). That work collided with the new region
  enumeration code that was tested with CXL 2.0 setups, and fails with
  crashes at startup.

  Lastly, the DOE (Data Object Exchange) implementation for retrieving
  an ACPI-like data table from CXL devices is being reworked for v6.4.
  Several fixes fell out of that work that are suitable for v6.3.

  All of this has been in linux-next for a while, and all reported
  issues [1] have been addressed.

  Summary:

   - Fix several issues with region enumeration in RCH topologies that
     can trigger crashes on driver startup or shutdown.

   - Fix CXL DVSEC range register compatibility versus region
     enumeration that leads to startup crashes

   - Fix CDAT endiannes handling

   - Fix multiple buffer handling boundary conditions

   - Fix Data Object Exchange (DOE) workqueue usage vs
     CONFIG_DEBUG_OBJECTS warn splats"

Link: http://lore.kernel.org/r/20230405075704.33de8121@canb.auug.org.au [1]

* tag 'cxl-fixes-6.3-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl:
  cxl/hdm: Extend DVSEC range register emulation for region enumeration
  cxl/hdm: Limit emulation to the number of range registers
  cxl/region: Move coherence tracking into cxl_region_attach()
  cxl/region: Fix region setup/teardown for RCDs
  cxl/port: Fix find_cxl_root() for RCDs and simplify it
  cxl/hdm: Skip emulation when driver manages mem_enable
  cxl/hdm: Fix double allocation of @cxlhdm
  PCI/DOE: Fix memory leak with CONFIG_DEBUG_OBJECTS=y
  PCI/DOE: Silence WARN splat with CONFIG_DEBUG_OBJECTS=y
  cxl/pci: Handle excessive CDAT length
  cxl/pci: Handle truncated CDAT entries
  cxl/pci: Handle truncated CDAT header
  cxl/pci: Fix CDAT retrieval on big endian

Pull cifs client fixes from Steve French:
 "Two cifs/smb3 client fixes, one for stable:

   - double lock fix for a cifs/smb1 reconnect path

   - DFS prefixpath fix for reconnect when server moved"

* tag '6.3-rc5-smb3-cifs-client-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: double lock in cifs_reconnect_tcon()
  cifs: sanitize paths in cifs_update_super_prepath.

Pull char/misc driver fixes from Greg KH:
 "Here are a small set of various small driver changes for 6.3-rc6.
  Included in here are:

   - iio driver fixes for reported problems

   - coresight hwtracing bugfix for reported problem

   - small counter driver bugfixes

  All have been in linux-next for a while with no reported problems"

* tag 'char-misc-6.3-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  coresight: etm4x: Do not access TRCIDR1 for identification
  coresight-etm4: Fix for() loop drvdata->nr_addr_cmp range bug
  iio: adc: ti-ads7950: Set `can_sleep` flag for GPIO chip
  iio: adc: palmas_gpadc: fix NULL dereference on rmmod
  counter: 104-quad-8: Fix Synapse action reported for Index signals
  counter: 104-quad-8: Fix race condition between FLAG and CNTR reads
  iio: adc: max11410: fix read_poll_timeout() usage
  iio: dac: cio-dac: Fix max DAC write value check for 12-bit
  iio: light: cm32181: Unregister second I2C client if present
  iio: accel: kionix-kx022a: Get the timestamp from the driver's private data in the trigger_handler
  iio: adc: ad7791: fix IRQ flags
  iio: buffer: make sure O_NONBLOCK is respected
  iio: buffer: correctly return bytes written in output buffers
  iio: light: vcnl4000: Fix WARN_ON on uninitialized lock
  iio: adis16480: select CONFIG_CRC32
  drivers: iio: adc: ltc2497: fix LSB shift
  iio: adc: qcom-spmi-adc5: Fix the channel name

Pull tty/serial driver fixes from Greg KH:
 "Here are some small tty and serial driver fixes for some reported
  problems:

   - fsl_uart driver bugfixes

   - sh-sci serial driver bugfixes

   - renesas serial driver DT binding bugfixes

   - 8250 DMA bugfix

  All of these have been in linux-next for a while with no reported
  problems"

* tag 'tty-6.3-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  tty: serial: sh-sci: Fix Rx on RZ/G2L SCI
  tty: serial: fsl_lpuart: fix crash in lpuart_uport_is_active
  tty: serial: fsl_lpuart: avoid checking for transfer complete when UARTCTRL_SBK is asserted in lpuart32_tx_empty
  serial: 8250: Prevent starting up DMA Rx on THRI interrupt
  dt-bindings: serial: renesas,scif: Fix 4th IRQ for 4-IRQ SCIFs
  tty: serial: sh-sci: Fix transmit end interrupt handler

Pull USB bugfixes from Greg KH:
 "Here are some small USB bugfixes for 6.3-rc6 that have been in my
  tree, and in linux-next, for a while. Included in here are:

   - new usb-serial driver device ids

   - xhci bugfixes for reported problems

   - gadget driver bugfixes for reported problems

   - dwc3 new device id

  All have been in linux-next with no reported problems"

* tag 'usb-6.3-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  usb: cdnsp: Fixes error: uninitialized symbol 'len'
  usb: gadgetfs: Fix ep_read_iter to handle ITER_UBUF
  usb: gadget: f_fs: Fix ffs_epfile_read_iter to handle ITER_UBUF
  usb: typec: altmodes/displayport: Fix configure initial pin assignment
  usb: dwc3: pci: add support for the Intel Meteor Lake-S
  xhci: Free the command allocated for setting LPM if we return early
  Revert "usb: xhci-pci: Set PROBE_PREFER_ASYNCHRONOUS"
  xhci: also avoid the XHCI_ZERO_64B_REGS quirk with a passthrough iommu
  USB: serial: option: add Quectel RM500U-CN modem
  usb: xhci: tegra: fix sleep in atomic call
  USB: serial: option: add Telit FE990 compositions
  USB: serial: cp210x: add Silicon Labs IFS-USB-DATACABLE IDs

Pull SCSI fixes from James Bottomley:
 "Four small fixes, all in drivers. They're all one or two lines except
  for the ufs one, but that's a simple revert of a previous feature"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: iscsi_tcp: Check that sock is valid before iscsi_set_param()
  scsi: qla2xxx: Fix memory leak in qla2x00_probe_one()
  scsi: mpi3mr: Handle soft reset in progress fault code (0xF002)
  scsi: Revert "scsi: ufs: core: Initialize devfreq synchronously"

Pull block fixes from Jens Axboe:

 - Ensure that ublk always reads the whole sqe upfront (me)

 - Fix for a block size probing issue with ublk (Ming)

 - Fix for the bio based polling (Keith)

 - NVMe pull request via Christoph:
      - fix discard support without oncs (Keith Busch)

 - Partition scan error handling regression fix (Yu)

* tag 'block-6.3-2023-04-06' of git://git.kernel.dk/linux:
  block: don't set GD_NEED_PART_SCAN if scan partition failed
  block: ublk: make sure that block size is set correctly
  ublk: read any SQE values upfront
  nvme: fix discard support without oncs
  blk-mq: directly poll requests

Pull io_uring fixes from Jens Axboe:
 "Just two minor fixes for provided buffers - one where we could
  potentially leak a buffer, and one where the returned values was
  off-by-one in some cases"

* tag 'io_uring-6.3-2023-04-06' of git://git.kernel.dk/linux:
  io_uring: fix memory leak when removing provided buffers
  io_uring: fix return value when removing provided buffers

Pull dma-mapping fix from Christoph Hellwig:

 - fix a braino in the swiotlb alignment check fix (Petr Tesarik)

* tag 'dma-mapping-6.3-2023-04-08' of git://git.infradead.org/users/hch/dma-mapping:
  swiotlb: fix a braino in the alignment check fix

Pull tracing fixes from Steven Rostedt:
 "A couple more minor fixes:

   - Reset direct->addr back to its original value on error in updating
     the direct trampoline code

   - Make lastcmd_mutex static"

* tag 'trace-v6.3-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing/synthetic: Make lastcmd_mutex static
  ftrace: Fix issue that 'direct->addr' not restored in modify_ftrace_direct()

Merge tag 'mm-hotfixes-stable-2023-04-07-16-23' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM fixes from Andrew Morton:
 "28 hotfixes.

  23 are cc:stable and the other five address issues which were
  introduced during this merge cycle.

  20 are for MM and the remainder are for other subsystems"

* tag 'mm-hotfixes-stable-2023-04-07-16-23' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (28 commits)
  maple_tree: fix a potential concurrency bug in RCU mode
  maple_tree: fix get wrong data_end in mtree_lookup_walk()
  mm/swap: fix swap_info_struct race between swapoff and get_swap_pages()
  nilfs2: fix sysfs interface lifetime
  mm: take a page reference when removing device exclusive entries
  mm: vmalloc: avoid warn_alloc noise caused by fatal signal
  nilfs2: initialize "struct nilfs_binfo_dat"->bi_pad field
  nilfs2: fix potential UAF of struct nilfs_sc_info in nilfs_segctor_thread()
  zsmalloc: document freeable stats
  zsmalloc: document new fullness grouping
  fsdax: force clear dirty mark if CoW
  mm/hugetlb: fix uffd wr-protection for CoW optimization path
  mm: enable maple tree RCU mode by default
  maple_tree: add RCU lock checking to rcu callback functions
  maple_tree: add smp_rmb() to dead node detection
  maple_tree: fix write memory barrier of nodes once dead for RCU mode
  maple_tree: remove extra smp_wmb() from mas_dead_leaves()
  maple_tree: fix freeing of nodes in rcu mode
  maple_tree: detect dead nodes in mas_start()
  maple_tree: be more cautious about dead nodes
  ...

Pull gpio fixes from Bartosz Golaszewski:

 - fix irq handling in gpio-davinci

 - fix Kconfig dependencies for gpio-regmap

* tag 'gpio-fixes-for-v6.3-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux:
  gpio: davinci: Add irq chip flag to skip set wake
  gpio: davinci: Do not clear the bank intr enable bit in save_context
  gpio: GPIO_REGMAP: select REGMAP instead of depending on it

Pull ACPI fixes from Rafael Wysocki:
 "Fix the ACPI backlight override mechanism for the cases when
  acpi_backlight=video is set through the kernel command line or a DMI
  quirk and add backlight quirks for Apple iMac14,1 and iMac14,2 and
  Lenovo ThinkPad W530 (Hans de Goede)"

* tag 'acpi-6.3-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI: video: Add acpi_backlight=video quirk for Lenovo ThinkPad W530
  ACPI: video: Add acpi_backlight=video quirk for Apple iMac14,1 and iMac14,2
  ACPI: video: Make acpi_backlight=video work independent from GPU driver
  ACPI: video: Add auto_detect arg to __acpi_video_get_backlight_type()