linux/Documentation/ABI
Linus Torvalds 5664896ba2 f2fs-for-5.16-rc1
In this cycle, we've applied relatively small number of patches which fix subtle
 corner cases mainly, while introducing a new mount option to be able to fragment
 the disk intentionally for performance tests.
 
 Enhancement:
  - add a mount option to fragmente on-disk layout to understand the performance
  - support direct IO for multi-partitions
  - add a fault injection of dquot_initialize
 
 Bug fix:
  - address some lockdep complaints
  - fix a deadlock issue with quota
  - fix a memory tuning condition
  - fix compression condition to improve the ratio
  - fix disabling compression on the non-empty compressed file
  - invalidate cached pages before IPU/DIO writes
 
 And, we've added some minor clean-ups as usual.
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Merge tag 'f2fs-for-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs

Pull f2fs updates from Jaegeuk Kim:
 "In this cycle, we've applied relatively small number of patches which
  fix subtle corner cases mainly, while introducing a new mount option
  to be able to fragment the disk intentionally for performance tests.

  Enhancements:

   - add a mount option to fragmente on-disk layout to understand the
     performance

   - support direct IO for multi-partitions

   - add a fault injection of dquot_initialize

  Bug fixes:

   - address some lockdep complaints

   - fix a deadlock issue with quota

   - fix a memory tuning condition

   - fix compression condition to improve the ratio

   - fix disabling compression on the non-empty compressed file

   - invalidate cached pages before IPU/DIO writes

  And, we've added some minor clean-ups as usual"

* tag 'f2fs-for-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs:
  f2fs: fix UAF in f2fs_available_free_memory
  f2fs: invalidate META_MAPPING before IPU/DIO write
  f2fs: support fault injection for dquot_initialize()
  f2fs: fix incorrect return value in f2fs_sanity_check_ckpt()
  f2fs: compress: disallow disabling compress on non-empty compressed file
  f2fs: compress: fix overwrite may reduce compress ratio unproperly
  f2fs: multidevice: support direct IO
  f2fs: introduce fragment allocation mode mount option
  f2fs: replace snprintf in show functions with sysfs_emit
  f2fs: include non-compressed blocks in compr_written_block
  f2fs: fix wrong condition to trigger background checkpoint correctly
  f2fs: fix to use WHINT_MODE
  f2fs: fix up f2fs_lookup tracepoints
  f2fs: set SBI_NEED_FSCK flag when inconsistent node block found
  f2fs: introduce excess_dirty_threshold()
  f2fs: avoid attaching SB_ACTIVE flag during mount
  f2fs: quota: fix potential deadlock
  f2fs: should use GFP_NOFS for directory inodes
2021-11-13 11:20:22 -08:00
..
obsolete ABI: obsolete/sysfs-bus-iio: add some missing blank lines 2021-09-28 12:48:15 +02:00
removed This was a reasonably active cycle for documentation; this pull includes: 2021-06-28 16:53:05 -07:00
stable Driver core changes for 5.16-rc1 2021-11-04 08:32:38 -07:00
testing f2fs-for-5.16-rc1 2021-11-13 11:20:22 -08:00
README docs: ABI: README: specify that files should be ReST compatible 2020-10-30 13:07:01 +01:00

This directory attempts to document the ABI between the Linux kernel and
userspace, and the relative stability of these interfaces.  Due to the
everchanging nature of Linux, and the differing maturity levels, these
interfaces should be used by userspace programs in different ways.

We have four different levels of ABI stability, as shown by the four
different subdirectories in this location.  Interfaces may change levels
of stability according to the rules described below.

The different levels of stability are:

  stable/
	This directory documents the interfaces that the developer has
	defined to be stable.  Userspace programs are free to use these
	interfaces with no restrictions, and backward compatibility for
	them will be guaranteed for at least 2 years.  Most interfaces
	(like syscalls) are expected to never change and always be
	available.

  testing/
	This directory documents interfaces that are felt to be stable,
	as the main development of this interface has been completed.
	The interface can be changed to add new features, but the
	current interface will not break by doing this, unless grave
	errors or security problems are found in them.  Userspace
	programs can start to rely on these interfaces, but they must be
	aware of changes that can occur before these interfaces move to
	be marked stable.  Programs that use these interfaces are
	strongly encouraged to add their name to the description of
	these interfaces, so that the kernel developers can easily
	notify them if any changes occur (see the description of the
	layout of the files below for details on how to do this.)

  obsolete/
	This directory documents interfaces that are still remaining in
	the kernel, but are marked to be removed at some later point in
	time.  The description of the interface will document the reason
	why it is obsolete and when it can be expected to be removed.

  removed/
	This directory contains a list of the old interfaces that have
	been removed from the kernel.

Every file in these directories will contain the following information:

What:		Short description of the interface
Date:		Date created
KernelVersion:	Kernel version this feature first showed up in.
Contact:	Primary contact for this interface (may be a mailing list)
Description:	Long description of the interface and how to use it.
Users:		All users of this interface who wish to be notified when
		it changes.  This is very important for interfaces in
		the "testing" stage, so that kernel developers can work
		with userspace developers to ensure that things do not
		break in ways that are unacceptable.  It is also
		important to get feedback for these interfaces to make
		sure they are working in a proper way and do not need to
		be changed further.


Note:
   The fields should be use a simple notation, compatible with ReST markup.
   Also, the file **should not** have a top-level index, like::

	===
	foo
	===

How things move between levels:

Interfaces in stable may move to obsolete, as long as the proper
notification is given.

Interfaces may be removed from obsolete and the kernel as long as the
documented amount of time has gone by.

Interfaces in the testing state can move to the stable state when the
developers feel they are finished.  They cannot be removed from the
kernel tree without going through the obsolete state first.

It's up to the developer to place their interfaces in the category they
wish for it to start out in.


Notable bits of non-ABI, which should not under any circumstances be considered
stable:

- Kconfig.  Userspace should not rely on the presence or absence of any
  particular Kconfig symbol, in /proc/config.gz, in the copy of .config
  commonly installed to /boot, or in any invocation of the kernel build
  process.

- Kernel-internal symbols.  Do not rely on the presence, absence, location, or
  type of any kernel symbol, either in System.map files or the kernel binary
  itself.  See Documentation/process/stable-api-nonsense.rst.