Merge tag 'docs-for-linus' of git://git.lwn.net/linux

Pull documentation update from Jon Corbet:
 "There is a nice new document from Neil on how pathname lookups work
  and some new CAN driver documentation.  Beyond that, we have
  kernel-doc fixes, a bit more work to support reproducible builds, and
  the usual collection of small fixes"

* tag 'docs-for-linus' of git://git.lwn.net/linux: (34 commits)
  Documentation: add new description of path-name lookup.
  Documentation/vm/slub.txt: document slabinfo-gnuplot.sh
  Doc: ABI/stable: Fix typo in ABI/stable
  doc: Clarify that nmi_watchdog param is for hardlockups
  Typo correction for description in gpio document.
  DocBook: Fix kernel-doc to be case-insensitive for private:
  kernel-docs.txt: update kernelnewbies reference
  Doc:kvm: Fix typo in Doc/virtual/kvm
  Documentation/Changes: Add bc in "Current Minimal Requirements" section
  Documentation/email-clients.txt: remove trailing whitespace
  DocBook: Use a fixed encoding for output
  MAINTAINERS: The docs tree has moved
  Docs/kernel-parameters: Add earlycon devicetree usage
  SubmittingPatches: make Subject examples match the de facto standard
  Documentation: gpio: mention that <function>-gpio has been deprecated
  Documentation: cgroups: just fix a few typos
  Documentation: Update kselftest.txt
  Documentation: DMA API: Be more explicit that nents is always the same
  Documentation: Update the default value of crashkernel low
  zram: update documentation
  ...

1 files changed, 40 insertions, 4 deletions

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 62435bb25266..5bda5031c83d 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -14,8 +14,43 @@ Statistics for individual zram devices are exported through sysfs nodes at
 
 * Usage
 
+There are several ways to configure and manage zram device(-s):
+a) using zram and zram_control sysfs attributes
+b) using zramctl utility, provided by util-linux (util-linux@vger.kernel.org).
+
+In this document we will describe only 'manual' zram configuration steps,
+IOW, zram and zram_control sysfs attributes.
+
+In order to get a better idea about zramctl please consult util-linux
+documentation, zramctl man-page or `zramctl --help'. Please be informed
+that zram maintainers do not develop/maintain util-linux or zramctl, should
+you have any questions please contact util-linux@vger.kernel.org
+
 Following shows a typical sequence of steps for using zram.
 
+WARNING
+=======
+For the sake of simplicity we skip error checking parts in most of the
+examples below. However, it is your sole responsibility to handle errors.
+
+zram sysfs attributes always return negative values in case of errors.
+The list of possible return codes:
+-EBUSY	-- an attempt to modify an attribute that cannot be changed once
+the device has been initialised. Please reset device first;
+-ENOMEM	-- zram was not able to allocate enough memory to fulfil your
+needs;
+-EINVAL	-- invalid input has been provided.
+
+If you use 'echo', the returned value that is changed by 'echo' utility,
+and, in general case, something like:
+
+	echo 3 > /sys/block/zram0/max_comp_streams
+	if [ $? -ne 0 ];
+		handle_error
+	fi
+
+should suffice.
+
 1) Load Module:
 	modprobe zram num_devices=4
 	This creates 4 devices: /dev/zram{0,1,2,3}
@@ -47,7 +82,7 @@ max_comp_streams adjustment.
 
 3) Select compression algorithm
 	Using comp_algorithm device attribute one can see available and
-	currently selected (shown in square brackets) compression algortithms,
+	currently selected (shown in square brackets) compression algorithms,
 	change selected compression algorithm (once the device is initialised
 	there is no way to change compression algorithm).
 
@@ -119,7 +154,7 @@ execute
 8) Stats:
 Per-device statistics are exported as various nodes under /sys/block/zram<id>/
 
-A brief description of exported device attritbutes. For more details please
+A brief description of exported device attributes. For more details please
 read Documentation/ABI/testing/sysfs-block-zram.
 
 Name            access            description
@@ -140,8 +175,9 @@ zero_pages        RO    the number of zero filled pages written to this disk
 orig_data_size    RO    uncompressed size of data stored in this disk
 compr_data_size   RO    compressed size of data stored in this disk
 mem_used_total    RO    the amount of memory allocated for this disk
-mem_used_max      RW    the maximum amount memory zram have consumed to
-                        store compressed data
+mem_used_max      RW    the maximum amount of memory zram have consumed to
+                        store the data (to reset this counter to the actual
+                        current value, write 1 to this attribute)
 mem_limit         RW    the maximum amount of memory ZRAM can use to store
                         the compressed data
 pages_compacted   RO    the number of pages freed during compaction