4 files changed, 75 insertions, 9 deletions
diff --git a/Documentation/admin-guide/acpi/fan_performance_states.rst b/Documentation/admin-guide/acpi/fan_performance_states.rst
new file mode 100644
index 000000000000..21d233ca50d8
--- /dev/null
+++ b/Documentation/admin-guide/acpi/fan_performance_states.rst
@@ -0,0 +1,62 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================
+ACPI Fan Performance States
+===========================
+
+When the optional _FPS object is present under an ACPI device representing a
+fan (for example, PNP0C0B or INT3404), the ACPI fan driver creates additional
+"state*" attributes in the sysfs directory of the ACPI device in question.
+These attributes list properties of fan performance states.
+
+For more information on _FPS refer to the ACPI specification at:
+
+http://uefi.org/specifications
+
+For instance, the contents of the INT3404 ACPI device sysfs directory
+may look as follows::
+
+ $ ls -l /sys/bus/acpi/devices/INT3404:00/
+ total 0
+...
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state0
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state1
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state10
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state11
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state2
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state3
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state4
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state5
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state6
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state7
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state8
+ -r--r--r-- 1 root root 4096 Dec 13 20:38 state9
+ -r--r--r-- 1 root root 4096 Dec 13 01:00 status
+ ...
+
+where each of the "state*" files represents one performance state of the fan
+and contains a colon-separated list of 5 integer numbers (fields) with the
+following interpretation::
+
+control_percent:trip_point_index:speed_rpm:noise_level_mdb:power_mw
+
+* ``control_percent``: The percent value to be used to set the fan speed to a
+  specific level using the _FSL object (0-100).
+
+* ``trip_point_index``: The active cooling trip point number that corresponds
+  to this performance state (0-9).
+
+* ``speed_rpm``: Speed of the fan in rotations per minute.
+
+* ``noise_level_mdb``: Audible noise emitted by the fan in this state in
+  millidecibels.
+
+* ``power_mw``: Power draw of the fan in this state in milliwatts.
+
+For example::
+
+ $cat /sys/bus/acpi/devices/INT3404:00/state1
+ 25:0:3200:12500:1250
+
+When a given field is not populated or its value provided by the platform
+firmware is invalid, the "not-defined" string is shown instead of the value.
diff --git a/Documentation/admin-guide/acpi/index.rst b/Documentation/admin-guide/acpi/index.rst
index 4d13eeea1eca..71277689ad97 100644
--- a/Documentation/admin-guide/acpi/index.rst
+++ b/Documentation/admin-guide/acpi/index.rst
@@ -12,3 +12,4 @@ the Linux ACPI support.
    dsdt-override
    ssdt-overlays
    cppc_sysfs
+   fan_performance_states
diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst
index 059ddcbe769d..9bc93f0ce0c9 100644
--- a/Documentation/admin-guide/ext4.rst
+++ b/Documentation/admin-guide/ext4.rst
@@ -181,14 +181,17 @@ When mounting an ext4 filesystem, the following option are accepted:
         system after its metadata has been committed to the journal.
 
   commit=nrsec	(*)
-        Ext4 can be told to sync all its data and metadata every 'nrsec'
-        seconds. The default value is 5 seconds.  This means that if you lose
-        your power, you will lose as much as the latest 5 seconds of work (your
-        filesystem will not be damaged though, thanks to the journaling).  This
-        default value (or any low value) will hurt performance, but it's good
-        for data-safety.  Setting it to 0 will have the same effect as leaving
-        it at the default (5 seconds).  Setting it to very large values will
-        improve performance.
+        This setting limits the maximum age of the running transaction to
+        'nrsec' seconds.  The default value is 5 seconds.  This means that if
+        you lose your power, you will lose as much as the latest 5 seconds of
+        metadata changes (your filesystem will not be damaged though, thanks
+        to the journaling). This default value (or any low value) will hurt
+        performance, but it's good for data-safety.  Setting it to 0 will have
+        the same effect as leaving it at the default (5 seconds).  Setting it
+        to very large values will improve performance.  Note that due to
+        delayed allocation even older data can be lost on power failure since
+        writeback of those data begins only after time set in
+        /proc/sys/vm/dirty_expire_centisecs.
 
   barrier=<0|1(*)>, barrier(*), nobarrier
         This enables/disables the use of write barriers in the jbd code.
diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst
index fb5b39f73059..ad911be5b5e9 100644
--- a/Documentation/admin-guide/xfs.rst
+++ b/Documentation/admin-guide/xfs.rst
@@ -253,7 +253,7 @@ The following sysctls are available for the XFS filesystem:
 	pool.
 
   fs.xfs.speculative_prealloc_lifetime
-		(Units: seconds   Min: 1  Default: 300  Max: 86400)
+	(Units: seconds   Min: 1  Default: 300  Max: 86400)
 	The interval at which the background scanning for inodes
 	with unused speculative preallocation runs. The scan
 	removes unused preallocation from clean inodes and releases