Merge "Merge android-4.14.111 (171fc237) into msm-4.14"

		The unit size is one block, now only support configuring in range

		of [1, 512].

What:          /sys/fs/f2fs/<disk>/umount_discard_timeout

Date:          January 2019

Contact:       "Jaegeuk Kim" <jaegeuk@kernel.org>

Description:

		Set timeout to issue discard commands during umount.

		Default: 5 secs

What:		/sys/fs/f2fs/<disk>/max_victim_search

Date:		January 2014

Contact:	"Jaegeuk Kim" <jaegeuk.kim@samsung.com>

* Use only NEON instructions, or VFP instructions that don't rely on support

  code

* Isolate your NEON code in a separate compilation unit, and compile it with

  '-mfpu=neon -mfloat-abi=softfp'

  '-march=armv7-a -mfpu=neon -mfloat-abi=softfp'

* Put kernel_neon_begin() and kernel_neon_end() calls around the calls into your

  NEON code

* Don't sleep in your NEON code, and be aware that it will be executed with

Therefore, the recommended and only supported way of using NEON/VFP in the

kernel is by adhering to the following rules:

* isolate the NEON code in a separate compilation unit and compile it with

  '-mfpu=neon -mfloat-abi=softfp';

  '-march=armv7-a -mfpu=neon -mfloat-abi=softfp';

* issue the calls to kernel_neon_begin(), kernel_neon_end() as well as the calls

  into the unit containing the NEON code from a compilation unit which is *not*

  built with the GCC flag '-mfpu=neon' set.

dm_bow (backup on write)

========================

dm_bow is a device mapper driver that uses the free space on a device to back up

data that is overwritten. The changes can then be committed by a simple state

change, or rolled back by removing the dm_bow device and running a command line

utility over the underlying device.

dm_bow has three states, set by writing ‘1’ or ‘2’ to /sys/block/dm-?/bow/state.

It is only possible to go from state 0 (initial state) to state 1, and then from

state 1 to state 2.

State 0: dm_bow collects all trims to the device and assumes that these mark

free space on the overlying file system that can be safely used. Typically the

mount code would create the dm_bow device, mount the file system, call the

FITRIM ioctl on the file system then switch to state 1. These trims are not

propagated to the underlying device.

State 1: All writes to the device cause the underlying data to be backed up to

the free (trimmed) area as needed in such a way as they can be restored.

However, the writes, with one exception, then happen exactly as they would

without dm_bow, so the device is always in a good final state. The exception is

that sector 0 is used to keep a log of the latest changes, both to indicate that

we are in this state and to allow rollback. See below for all details. If there

isn't enough free space, writes are failed with -ENOSPC.

State 2: The transition to state 2 triggers replacing the special sector 0 with

the normal sector 0, and the freeing of all state information. dm_bow then

becomes a pass-through driver, allowing the device to continue to be used with

minimal performance impact.

Usage

=====

dm-bow takes one command line parameter, the name of the underlying device.

dm-bow will typically be used in the following way. dm-bow will be loaded with a

suitable underlying device and the resultant device will be mounted. A file

system trim will be issued via the FITRIM ioctl, then the device will be

switched to state 1. The file system will now be used as normal. At some point,

the changes can either be committed by switching to state 2, or rolled back by

unmounting the file system, removing the dm-bow device and running the command

line utility. Note that rebooting the device will be equivalent to unmounting

and removing, but the command line utility must still be run

Details of operation in state 1

===============================

dm_bow maintains a type for all sectors. A sector can be any of:

SECTOR0

SECTOR0_CURRENT

UNCHANGED

FREE

CHANGED

BACKUP

SECTOR0 is the first sector on the device, and is used to hold the log of

changes. This is the one exception.

SECTOR0_CURRENT is a sector picked from the FREE sectors, and is where reads and

writes from the true sector zero are redirected to. Note that like any backup

sector, if the sector is written to directly, it must be moved again.

UNCHANGED means that the sector has not been changed since we entered state 1.

Thus if it is written to or trimmed, the contents must first be backed up.

FREE means that the sector was trimmed in state 0 and has not yet been written

to or used for backup. On being written to, a FREE sector is changed to CHANGED.

CHANGED means that the sector has been modified, and can be further modified

without further backup.

BACKUP means that this is a free sector being used as a backup. On being written

to, the contents must first be backed up again.

All backup operations are logged to the first sector. The log sector has the

format:

--------------------------------------------------------

| Magic | Count | Sequence | Log entry | Log entry | …

--------------------------------------------------------

Magic is a magic number. Count is the number of log entries. Sequence is 0

initially. A log entry is

-----------------------------------

| Source | Dest | Size | Checksum |

-----------------------------------

When SECTOR0 is full, the log sector is backed up and another empty log sector

created with sequence number one higher. The first entry in any log entry with

sequence > 0 therefore must be the log of the backing up of the previous log

sector. Note that sequence is not strictly needed, but is a useful sanity check

and potentially limits the time spent trying to restore a corrupted snapshot.

On entering state 1, dm_bow has a list of free sectors. All other sectors are

unchanged. Sector0_current is selected from the free sectors and the contents of

sector 0 are copied there. The sector 0 is backed up, which triggers the first

log entry to be written.

                       does not aware of cold files such as media files.

inline_xattr           Enable the inline xattrs feature.

noinline_xattr         Disable the inline xattrs feature.

inline_xattr_size=%u   Support configuring inline xattr size, it depends on

		       flexible inline xattr feature.

inline_data            Enable the inline data feature: New created small(<~3.4k)

                       files can be written into inode block.

inline_dentry          Enable the inline dir feature: data in new created

:Author: Randy Dunlap <rdunlap@infradead.org>

:Author: Andrew Murray <amurray@mpc-data.co.uk>

Integer types

=============

Raw pointer value SHOULD be printed with %p. The kernel supports

the following extended format specifiers for pointer types:

Pointer Types

=============

Pointers printed without a specifier extension (i.e unadorned %p) are

hashed to give a unique identifier without leaking kernel addresses to user

space. On 64 bit machines the first 32 bits are zeroed. If you _really_

want the address see %px below.

::

	%p	abcdef12 or 00000000abcdef12

Symbols/Function Pointers

=========================

	printk("Faulted at %pS\n", (void *)regs->ip);

	printk(" %s%pB\n", (reliable ? "" : "? "), (void *)*stack);

Kernel Pointers

===============

::

	%pK	0x01234567 or 0x0123456789abcdef

	%pK	01234567 or 0123456789abcdef

For printing kernel pointers which should be hidden from unprivileged

users. The behaviour of ``%pK`` depends on the ``kptr_restrict sysctl`` - see

Documentation/sysctl/kernel.txt for more details.

Unmodified Addresses

====================

::

	%px	01234567 or 0123456789abcdef

For printing pointers when you _really_ want to print the address. Please

consider whether or not you are leaking sensitive information about the

Kernel layout in memory before printing pointers with %px. %px is

functionally equivalent to %lx. %px is preferred to %lx because it is more

uniquely grep'able. If, in the future, we need to modify the way the Kernel

handles printing pointers it will be nice to be able to find the call

sites.

Struct Resources

================