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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-26 22:24:09 +08:00
linux-next/Documentation/ABI
Linus Torvalds 274c0e74e5 f2fs-for-4.17-rc1
In this round, we've mainly focused on performance tuning and critical bug fixes
 occurred in low-end devices. Sheng Yong introduced lost_found feature to keep
 missing files during recovery instead of thrashing them. We're preparing coming
 fsverity implementation. And, we've got more features to communicate with users
 for better performance. In low-end devices, some memory-related issues were
 fixed, and subtle race condtions and corner cases were addressed as well.
 
 Enhancement:
  - large nat bitmaps for more free node ids
  - add three block allocation policies to pass down write hints given by user
  - expose extension list to user and introduce hot file extension
  - tune small devices seamlessly for low-end devices
  - set readdir_ra by default
  - give more resources under gc_urgent mode regarding to discard and cleaning
  - introduce fsync_mode to enforce posix or not
  - nowait aio support
  - add lost_found feature to keep dangling inodes
  - reserve bits for future fsverity feature
  - add test_dummy_encryption for FBE
 
 Bug fix:
  - don't use highmem for dentry pages
  - align memory boundary for bitops
  - truncate preallocated blocks in write errors
  - guarantee i_times on fsync call
  - clear CP_TRIMMED_FLAG correctly
  - prevent node chain loop during recovery
  - avoid data race between atomic write and background cleaning
  - avoid unnecessary selinux violation warnings on resgid option
  - GFP_NOFS to avoid deadlock in quota and read paths
  - fix f2fs_skip_inode_update to allow i_size recovery
 
 In addition to them, there are several minor bug fixes and clean-ups.
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Merge tag 'f2fs-for-4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs

Pull f2fs update from Jaegeuk Kim:
 "In this round, we've mainly focused on performance tuning and critical
  bug fixes occurred in low-end devices. Sheng Yong introduced
  lost_found feature to keep missing files during recovery instead of
  thrashing them. We're preparing coming fsverity implementation. And,
  we've got more features to communicate with users for better
  performance. In low-end devices, some memory-related issues were
  fixed, and subtle race condtions and corner cases were addressed as
  well.

  Enhancements:
   - large nat bitmaps for more free node ids
   - add three block allocation policies to pass down write hints given by user
   - expose extension list to user and introduce hot file extension
   - tune small devices seamlessly for low-end devices
   - set readdir_ra by default
   - give more resources under gc_urgent mode regarding to discard and cleaning
   - introduce fsync_mode to enforce posix or not
   - nowait aio support
   - add lost_found feature to keep dangling inodes
   - reserve bits for future fsverity feature
   - add test_dummy_encryption for FBE

  Bug fixes:
   - don't use highmem for dentry pages
   - align memory boundary for bitops
   - truncate preallocated blocks in write errors
   - guarantee i_times on fsync call
   - clear CP_TRIMMED_FLAG correctly
   - prevent node chain loop during recovery
   - avoid data race between atomic write and background cleaning
   - avoid unnecessary selinux violation warnings on resgid option
   - GFP_NOFS to avoid deadlock in quota and read paths
   - fix f2fs_skip_inode_update to allow i_size recovery

  In addition to the above, there are several minor bug fixes and clean-ups"

* tag 'f2fs-for-4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (50 commits)
  f2fs: remain written times to update inode during fsync
  f2fs: make assignment of t->dentry_bitmap more readable
  f2fs: truncate preallocated blocks in error case
  f2fs: fix a wrong condition in f2fs_skip_inode_update
  f2fs: reserve bits for fs-verity
  f2fs: Add a segment type check in inplace write
  f2fs: no need to initialize zero value for GFP_F2FS_ZERO
  f2fs: don't track new nat entry in nat set
  f2fs: clean up with F2FS_BLK_ALIGN
  f2fs: check blkaddr more accuratly before issue a bio
  f2fs: Set GF_NOFS in read_cache_page_gfp while doing f2fs_quota_read
  f2fs: introduce a new mount option test_dummy_encryption
  f2fs: introduce F2FS_FEATURE_LOST_FOUND feature
  f2fs: release locks before return in f2fs_ioc_gc_range()
  f2fs: align memory boundary for bitops
  f2fs: remove unneeded set_cold_node()
  f2fs: add nowait aio support
  f2fs: wrap all options with f2fs_sb_info.mount_opt
  f2fs: Don't overwrite all types of node to keep node chain
  f2fs: introduce mount option for fsync mode
  ...
2018-04-05 19:12:55 -07:00
..
obsolete This is the bulk of GPIO changes for the v4.15 kernel cycle: 2017-11-14 17:23:44 -08:00
removed
stable Char/Misc patches for 4.17-rc1 2018-04-04 20:07:20 -07:00
testing f2fs-for-4.17-rc1 2018-04-05 19:12:55 -07:00
README docs: fix locations of several documents that got moved 2016-10-24 08:12:35 -02:00

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.


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.