Merge tag 'v4.15-rc4' into perf/core, to pick up fixes

| Qualcomm Tech. | Falkor v1       | E1003           | QCOM_FALKOR_ERRATUM_1003    |

| Qualcomm Tech. | Falkor v1       | E1009           | QCOM_FALKOR_ERRATUM_1009    |

| Qualcomm Tech. | QDF2400 ITS     | E0065           | QCOM_QDF2400_ERRATUM_0065   |

| Qualcomm Tech. | Falkor v{1,2}   | E1041           | QCOM_FALKOR_ERRATUM_1041    |

normal scheduling policy and absolute bandwidth allocation model for

realtime scheduling policy.

WARNING: cgroup2 doesn't yet support control of realtime processes and

the cpu controller can only be enabled when all RT processes are in

the root cgroup.  Be aware that system management software may already

have placed RT processes into nonroot cgroups during the system boot

process, and these processes may need to be moved to the root cgroup

before the cpu controller can be enabled.

CPU Interface Files

~~~~~~~~~~~~~~~~~~~

   root of the overlay.  Finally the directory is moved to the new

   location.

There are several ways to tune the "redirect_dir" feature.

Kernel config options:

- OVERLAY_FS_REDIRECT_DIR:

    If this is enabled, then redirect_dir is turned on by  default.

- OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW:

    If this is enabled, then redirects are always followed by default. Enabling

    this results in a less secure configuration.  Enable this option only when

    worried about backward compatibility with kernels that have the redirect_dir

    feature and follow redirects even if turned off.

Module options (can also be changed through /sys/module/overlay/parameters/*):

- "redirect_dir=BOOL":

    See OVERLAY_FS_REDIRECT_DIR kernel config option above.

- "redirect_always_follow=BOOL":

    See OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW kernel config option above.

- "redirect_max=NUM":

    The maximum number of bytes in an absolute redirect (default is 256).

Mount options:

- "redirect_dir=on":

    Redirects are enabled.

- "redirect_dir=follow":

    Redirects are not created, but followed.

- "redirect_dir=off":

    Redirects are not created and only followed if "redirect_always_follow"

    feature is enabled in the kernel/module config.

- "redirect_dir=nofollow":

    Redirects are not created and not followed (equivalent to "redirect_dir=off"

    if "redirect_always_follow" feature is not enabled).

Non-directories

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

original compressor.  Once all pages are removed from an old zpool, the zpool

and its compressor are freed.

Some of the pages in zswap are same-value filled pages (i.e. contents of the

page have same value or repetitive pattern). These pages include zero-filled

pages and they are handled differently. During store operation, a page is

checked if it is a same-value filled page before compressing it. If true, the

compressed length of the page is set to zero and the pattern or same-filled

value is stored.

Same-value filled pages identification feature is enabled by default and can be

disabled at boot time by setting the "same_filled_pages_enabled" attribute to 0,

e.g. zswap.same_filled_pages_enabled=0. It can also be enabled and disabled at

runtime using the sysfs "same_filled_pages_enabled" attribute, e.g.

echo 1 > /sys/module/zswap/parameters/same_filled_pages_enabled

When zswap same-filled page identification is disabled at runtime, it will stop

checking for the same-value filled pages during store operation. However, the

existing pages which are marked as same-value filled pages remain stored

unchanged in zswap until they are either loaded or invalidated.

A debugfs interface is provided for various statistic about pool size, number

of pages stored, and various counters for the reasons pages are rejected.

of pages stored, same-value filled pages and various counters for the reasons

pages are rejected.