Merge remote-tracking branch 'mauro-exp/docbook3' into death-to-docbook

	- How to do DMA with ISA (and LPC) devices.

DMA-attributes.txt

	- listing of the various possible attributes a DMA region can have

DocBook/

	- directory with DocBook templates etc. for kernel documentation.

EDID/

	- directory with info on customizing EDID for broken gfx/displays.

IPMI.txt

	- basic info on the Intel IOMMU virtualization support.

Makefile

	- It's not of interest for those who aren't touching the build system.

Makefile.sphinx

	- It's not of interest for those who aren't touching the build system.

PCI/

	- info related to PCI drivers.

RCU/

	- full colour GIF image of Linux logo (penguin - Tux).

logo.txt

	- info on creator of above logo & site to get additional images from.

lsm.txt

	- Linux Security Modules: General Security Hooks for Linux

lzo.txt

	- kernel LZO decompressor input formats

m68k/

*.xml

*.ps

*.pdf

*.html

*.9.gz

*.9

*.aux

*.dvi

*.log

*.out

*.png

*.gif

*.svg

*.proc

*.db

media-indices.tmpl

media-entities.tmpl

###

# This makefile is used to generate the kernel documentation,

# primarily based on in-line comments in various source files.

# See Documentation/kernel-doc-nano-HOWTO.txt for instruction in how

# to document the SRC - and how to read it.

# To add a new book the only step required is to add the book to the

# list of DOCBOOKS.

DOCBOOKS := z8530book.xml  \

	    kernel-hacking.xml kernel-locking.xml \

	    networking.xml \

	    filesystems.xml lsm.xml kgdb.xml \

	    libata.xml mtdnand.xml librs.xml rapidio.xml \

	    s390-drivers.xml scsi.xml \

	    sh.xml w1.xml

ifeq ($(DOCBOOKS),)

# Skip DocBook build if the user explicitly requested no DOCBOOKS.

.DEFAULT:

	@echo "  SKIP    DocBook $@ target (DOCBOOKS=\"\" specified)."

else

ifneq ($(SPHINXDIRS),)

# Skip DocBook build if the user explicitly requested a sphinx dir

.DEFAULT:

	@echo "  SKIP    DocBook $@ target (SPHINXDIRS specified)."

else

###

# The build process is as follows (targets):

#              (xmldocs) [by docproc]

# file.tmpl --> file.xml +--> file.ps   (psdocs)   [by db2ps or xmlto]

#                        +--> file.pdf  (pdfdocs)  [by db2pdf or xmlto]

#                        +--> DIR=file  (htmldocs) [by xmlto]

#                        +--> man/      (mandocs)  [by xmlto]

# for PDF and PS output you can choose between xmlto and docbook-utils tools

PDF_METHOD	= $(prefer-db2x)

PS_METHOD	= $(prefer-db2x)

targets += $(DOCBOOKS)

BOOKS := $(addprefix $(obj)/,$(DOCBOOKS))

xmldocs: $(BOOKS)

sgmldocs: xmldocs

PS := $(patsubst %.xml, %.ps, $(BOOKS))

psdocs: $(PS)

PDF := $(patsubst %.xml, %.pdf, $(BOOKS))

pdfdocs: $(PDF)

HTML := $(sort $(patsubst %.xml, %.html, $(BOOKS)))

htmldocs: $(HTML)

	$(call cmd,build_main_index)

MAN := $(patsubst %.xml, %.9, $(BOOKS))

mandocs: $(MAN)

	find $(obj)/man -name '*.9' | xargs gzip -nf

# Default location for installed man pages

export INSTALL_MAN_PATH = $(objtree)/usr

installmandocs: mandocs

	mkdir -p $(INSTALL_MAN_PATH)/man/man9/

	find $(obj)/man -name '*.9.gz' -printf '%h %f\n' | \

		sort -k 2 -k 1 | uniq -f 1 | sed -e 's: :/:' | \

		xargs install -m 644 -t $(INSTALL_MAN_PATH)/man/man9/

# no-op for the DocBook toolchain

epubdocs:

latexdocs:

linkcheckdocs:

###

#External programs used

KERNELDOCXMLREF = $(srctree)/scripts/kernel-doc-xml-ref

KERNELDOC       = $(srctree)/scripts/kernel-doc

DOCPROC         = $(objtree)/scripts/docproc

CHECK_LC_CTYPE = $(objtree)/scripts/check-lc_ctype

# Use a fixed encoding - UTF-8 if the C library has support built-in

# or ASCII if not

LC_CTYPE := $(call try-run, LC_CTYPE=C.UTF-8 $(CHECK_LC_CTYPE),C.UTF-8,C)

export LC_CTYPE

XMLTOFLAGS = -m $(srctree)/$(src)/stylesheet.xsl

XMLTOFLAGS += --skip-validation

###

# DOCPROC is used for two purposes:

# 1) To generate a dependency list for a .tmpl file

# 2) To preprocess a .tmpl file and call kernel-doc with

#     appropriate parameters.

# The following rules are used to generate the .xml documentation

# required to generate the final targets. (ps, pdf, html).

quiet_cmd_docproc = DOCPROC $@

      cmd_docproc = SRCTREE=$(srctree)/ $(DOCPROC) doc $< >$@

define rule_docproc

	set -e;								\

        $(if $($(quiet)cmd_$(1)),echo '  $($(quiet)cmd_$(1))';) 	\

        $(cmd_$(1)); 							\

        ( 								\

          echo 'cmd_$@ := $(cmd_$(1))'; 				\

          echo $@: `SRCTREE=$(srctree) $(DOCPROC) depend $<`; 		\

        ) > $(dir $@).$(notdir $@).cmd

endef

%.xml: %.tmpl $(KERNELDOC) $(DOCPROC) $(KERNELDOCXMLREF) FORCE

	$(call if_changed_rule,docproc)

# Tell kbuild to always build the programs

always := $(hostprogs-y)

notfoundtemplate = echo "*** You have to install docbook-utils or xmlto ***"; \

		   exit 1

db2xtemplate = db2TYPE -o $(dir $@) $<

xmltotemplate = xmlto TYPE $(XMLTOFLAGS) -o $(dir $@) $<

# determine which methods are available

ifeq ($(shell which db2ps >/dev/null 2>&1 && echo found),found)

	use-db2x = db2x

	prefer-db2x = db2x

else

	use-db2x = notfound

	prefer-db2x = $(use-xmlto)

endif

ifeq ($(shell which xmlto >/dev/null 2>&1 && echo found),found)

	use-xmlto = xmlto

	prefer-xmlto = xmlto

else

	use-xmlto = notfound

	prefer-xmlto = $(use-db2x)

endif

# the commands, generated from the chosen template

quiet_cmd_db2ps = PS      $@

      cmd_db2ps = $(subst TYPE,ps, $($(PS_METHOD)template))

%.ps : %.xml

	$(call cmd,db2ps)

quiet_cmd_db2pdf = PDF     $@

      cmd_db2pdf = $(subst TYPE,pdf, $($(PDF_METHOD)template))

%.pdf : %.xml

	$(call cmd,db2pdf)

index = index.html

main_idx = $(obj)/$(index)

quiet_cmd_build_main_index = HTML    $(main_idx)

      cmd_build_main_index = rm -rf $(main_idx); \

		   echo '<h1>Linux Kernel HTML Documentation</h1>' >> $(main_idx) && \

		   echo '<h2>Kernel Version: $(KERNELVERSION)</h2>' >> $(main_idx) && \

		   cat $(HTML) >> $(main_idx)

quiet_cmd_db2html = HTML    $@

      cmd_db2html = xmlto html $(XMLTOFLAGS) -o $(patsubst %.html,%,$@) $< && \

		echo '<a HREF="$(patsubst %.html,%,$(notdir $@))/index.html"> \

		$(patsubst %.html,%,$(notdir $@))</a><p>' > $@

###

# Rules to create an aux XML and .db, and use them to re-process the DocBook XML

# to fill internal hyperlinks

       gen_aux_xml = :

 quiet_gen_aux_xml = echo '  XMLREF  $@'

silent_gen_aux_xml = :

%.aux.xml: %.xml

	@$($(quiet)gen_aux_xml)

	@rm -rf $@

	@(cat $< | egrep "^<refentry id" | egrep -o "\".*\"" | cut -f 2 -d \" > $<.db)

	@$(KERNELDOCXMLREF) -db $<.db $< > $@

.PRECIOUS: %.aux.xml

%.html:	%.aux.xml

	@(which xmlto > /dev/null 2>&1) || \

	 (echo "*** You need to install xmlto ***"; \

	  exit 1)

	@rm -rf $@ $(patsubst %.html,%,$@)

	$(call cmd,db2html)

	@if [ ! -z "$(PNG-$(basename $(notdir $@)))" ]; then \

            cp $(PNG-$(basename $(notdir $@))) $(patsubst %.html,%,$@); fi

quiet_cmd_db2man = MAN     $@

      cmd_db2man = if grep -q refentry $<; then xmlto man $(XMLTOFLAGS) -o $(obj)/man/$(*F) $< ; fi

%.9 : %.xml

	@(which xmlto > /dev/null 2>&1) || \

	 (echo "*** You need to install xmlto ***"; \

	  exit 1)

	$(Q)mkdir -p $(obj)/man/$(*F)

	$(call cmd,db2man)

	@touch $@

###

# Rules to generate postscripts and PNG images from .fig format files

quiet_cmd_fig2eps = FIG2EPS $@

      cmd_fig2eps = fig2dev -Leps $< $@

%.eps: %.fig

	@(which fig2dev > /dev/null 2>&1) || \

	 (echo "*** You need to install transfig ***"; \

	  exit 1)

	$(call cmd,fig2eps)

quiet_cmd_fig2png = FIG2PNG $@

      cmd_fig2png = fig2dev -Lpng $< $@

%.png: %.fig

	@(which fig2dev > /dev/null 2>&1) || \

	 (echo "*** You need to install transfig ***"; \

	  exit 1)

	$(call cmd,fig2png)

###

# Rule to convert a .c file to inline XML documentation

       gen_xml = :

 quiet_gen_xml = echo '  GEN     $@'

silent_gen_xml = :

%.xml: %.c

	@$($(quiet)gen_xml)

	@(                            \

	   echo "<programlisting>";   \

	   expand --tabs=8 < $< |     \

	   sed -e "s/&/\\&/g"     \

	       -e "s/</\\&lt;/g"      \

	       -e "s/>/\\>/g";     \

	   echo "</programlisting>")  > $@

endif # DOCBOOKS=""

endif # SPHINDIR=...

###

# Help targets as used by the top-level makefile

dochelp:

	@echo  ' Linux kernel internal documentation in different formats (DocBook):'

	@echo  '  htmldocs        - HTML'

	@echo  '  pdfdocs         - PDF'

	@echo  '  psdocs          - Postscript'

	@echo  '  xmldocs         - XML DocBook'

	@echo  '  mandocs         - man pages'

	@echo  '  installmandocs  - install man pages generated by mandocs to INSTALL_MAN_PATH'; \

	 echo  '                    (default: $(INSTALL_MAN_PATH))'; \

	 echo  ''

	@echo  '  cleandocs       - clean all generated DocBook files'

	@echo

	@echo  '  make DOCBOOKS="s1.xml s2.xml" [target] Generate only docs s1.xml s2.xml'

	@echo  '  valid values for DOCBOOKS are: $(DOCBOOKS)'

	@echo

	@echo  "  make DOCBOOKS=\"\" [target] Don't generate docs from Docbook"

	@echo  '     This is useful to generate only the ReST docs (Sphinx)'

###

# Temporary files left by various tools

clean-files := $(DOCBOOKS) \

	$(patsubst %.xml, %.dvi,     $(DOCBOOKS)) \

	$(patsubst %.xml, %.aux,     $(DOCBOOKS)) \

	$(patsubst %.xml, %.tex,     $(DOCBOOKS)) \

	$(patsubst %.xml, %.log,     $(DOCBOOKS)) \

	$(patsubst %.xml, %.out,     $(DOCBOOKS)) \

	$(patsubst %.xml, %.ps,      $(DOCBOOKS)) \

	$(patsubst %.xml, %.pdf,     $(DOCBOOKS)) \

	$(patsubst %.xml, %.html,    $(DOCBOOKS)) \

	$(patsubst %.xml, %.9,       $(DOCBOOKS)) \

	$(patsubst %.xml, %.aux.xml, $(DOCBOOKS)) \

	$(patsubst %.xml, %.xml.db,  $(DOCBOOKS)) \

	$(patsubst %.xml, %.xml,     $(DOCBOOKS)) \

	$(patsubst %.xml, .%.xml.cmd, $(DOCBOOKS)) \

	$(index)

clean-dirs := $(patsubst %.xml,%,$(DOCBOOKS)) man

cleandocs:

	$(Q)rm -f $(call objectify, $(clean-files))

	$(Q)rm -rf $(call objectify, $(clean-dirs))

# Declare the contents of the .PHONY variable as phony.  We keep that

# information in a variable so we can use it in if_changed and friends.

.PHONY: $(PHONY)

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"

	"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>

<book id="Linux-filesystems-API">

 <bookinfo>

  <title>Linux Filesystems API</title>

  <legalnotice>

   <para>

     This documentation is free software; you can redistribute

     it and/or modify it under the terms of the GNU General Public

     License as published by the Free Software Foundation; either

     version 2 of the License, or (at your option) any later

     version.

   </para>

   <para>

     This program is distributed in the hope that it will be

     useful, but WITHOUT ANY WARRANTY; without even the implied

     warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

     See the GNU General Public License for more details.

   </para>

   <para>

     You should have received a copy of the GNU General Public

     License along with this program; if not, write to the Free

     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,

     MA 02111-1307 USA

   </para>

   <para>

     For more details see the file COPYING in the source

     distribution of Linux.

   </para>

  </legalnotice>

 </bookinfo>

<toc></toc>

  <chapter id="vfs">

     <title>The Linux VFS</title>

     <sect1 id="the_filesystem_types"><title>The Filesystem types</title>

!Iinclude/linux/fs.h

     </sect1>

     <sect1 id="the_directory_cache"><title>The Directory Cache</title>

!Efs/dcache.c

!Iinclude/linux/dcache.h

     </sect1>

     <sect1 id="inode_handling"><title>Inode Handling</title>

!Efs/inode.c

!Efs/bad_inode.c

     </sect1>

     <sect1 id="registration_and_superblocks"><title>Registration and Superblocks</title>

!Efs/super.c

     </sect1>

     <sect1 id="file_locks"><title>File Locks</title>

!Efs/locks.c

!Ifs/locks.c

     </sect1>

     <sect1 id="other_functions"><title>Other Functions</title>

!Efs/mpage.c

!Efs/namei.c

!Efs/buffer.c

!Eblock/bio.c

!Efs/seq_file.c

!Efs/filesystems.c

!Efs/fs-writeback.c

!Efs/block_dev.c

     </sect1>

  </chapter>

  <chapter id="proc">

     <title>The proc filesystem</title>

     <sect1 id="sysctl_interface"><title>sysctl interface</title>

!Ekernel/sysctl.c

     </sect1>

     <sect1 id="proc_filesystem_interface"><title>proc filesystem interface</title>

!Ifs/proc/base.c

     </sect1>

  </chapter>

  <chapter id="fs_events">

     <title>Events based on file descriptors</title>

!Efs/eventfd.c

  </chapter>

  <chapter id="sysfs">

     <title>The Filesystem for Exporting Kernel Objects</title>

!Efs/sysfs/file.c

!Efs/sysfs/symlink.c

  </chapter>

  <chapter id="debugfs">

     <title>The debugfs filesystem</title>

     <sect1 id="debugfs_interface"><title>debugfs interface</title>

!Efs/debugfs/inode.c

!Efs/debugfs/file.c

     </sect1>

  </chapter>

  <chapter id="LinuxJDBAPI">

  <chapterinfo>

  <title>The Linux Journalling API</title>

  <authorgroup>

  <author>

     <firstname>Roger</firstname>

     <surname>Gammans</surname>

     <affiliation>

     <address>

      <email>rgammans@computer-surgery.co.uk</email>

     </address>

    </affiliation>

     </author>

  </authorgroup>

  <authorgroup>

   <author>

    <firstname>Stephen</firstname>

    <surname>Tweedie</surname>

    <affiliation>

     <address>

      <email>sct@redhat.com</email>

     </address>

    </affiliation>

   </author>

  </authorgroup>

  <copyright>

   <year>2002</year>

   <holder>Roger Gammans</holder>

  </copyright>

  </chapterinfo>

  <title>The Linux Journalling API</title>

    <sect1 id="journaling_overview">

     <title>Overview</title>

    <sect2 id="journaling_details">

     <title>Details</title>

<para>

The journalling layer is  easy to use. You need to

first of all create a journal_t data structure. There are

two calls to do this dependent on how you decide to allocate the physical

media on which the journal resides. The jbd2_journal_init_inode() call

is for journals stored in filesystem inodes, or the jbd2_journal_init_dev()

call can be used for journal stored on a raw device (in a continuous range

of blocks). A journal_t is a typedef for a struct pointer, so when

you are finally finished make sure you call jbd2_journal_destroy() on it

to free up any used kernel memory.

</para>

<para>

Once you have got your journal_t object you need to 'mount' or load the journal

file. The journalling layer expects the space for the journal was already

allocated and initialized properly by the userspace tools.  When loading the

journal you must call jbd2_journal_load() to process journal contents.  If the

client file system detects the journal contents does not need to be processed

(or even need not have valid contents), it may call jbd2_journal_wipe() to

clear the journal contents before calling jbd2_journal_load().

</para>

<para>

Note that jbd2_journal_wipe(..,0) calls jbd2_journal_skip_recovery() for you if

it detects any outstanding transactions in the journal and similarly

jbd2_journal_load() will call jbd2_journal_recover() if necessary.  I would

advise reading ext4_load_journal() in fs/ext4/super.c for examples on this

stage.

</para>

<para>

Now you can go ahead and start modifying the underlying

filesystem. Almost.

</para>

<para>

You still need to actually journal your filesystem changes, this

is done by wrapping them into transactions. Additionally you

also need to wrap the modification of each of the buffers

with calls to the journal layer, so it knows what the modifications

you are actually making are. To do this use jbd2_journal_start() which

returns a transaction handle.

</para>

<para>

jbd2_journal_start()

and its counterpart jbd2_journal_stop(), which indicates the end of a

transaction are nestable calls, so you can reenter a transaction if necessary,

but remember you must call jbd2_journal_stop() the same number of times as

jbd2_journal_start() before the transaction is completed (or more accurately

leaves the update phase). Ext4/VFS makes use of this feature to simplify

handling of inode dirtying, quota support, etc.

</para>

<para>

Inside each transaction you need to wrap the modifications to the

individual buffers (blocks). Before you start to modify a buffer you

need to call jbd2_journal_get_{create,write,undo}_access() as appropriate,

this allows the journalling layer to copy the unmodified data if it

needs to. After all the buffer may be part of a previously uncommitted

transaction.

At this point you are at last ready to modify a buffer, and once

you are have done so you need to call jbd2_journal_dirty_{meta,}data().

Or if you've asked for access to a buffer you now know is now longer

required to be pushed back on the device you can call jbd2_journal_forget()

in much the same way as you might have used bforget() in the past.

</para>

<para>

A jbd2_journal_flush() may be called at any time to commit and checkpoint

all your transactions.

</para>

<para>

Then at umount time , in your put_super() you can then call jbd2_journal_destroy()

to clean up your in-core journal object.

</para>

<para>

Unfortunately there a couple of ways the journal layer can cause a deadlock.

The first thing to note is that each task can only have

a single outstanding transaction at any one time, remember nothing

commits until the outermost jbd2_journal_stop(). This means

you must complete the transaction at the end of each file/inode/address

etc. operation you perform, so that the journalling system isn't re-entered

on another journal. Since transactions can't be nested/batched

across differing journals, and another filesystem other than

yours (say ext4) may be modified in a later syscall.

</para>

<para>

The second case to bear in mind is that jbd2_journal_start() can

block if there isn't enough space in the journal for your transaction

(based on the passed nblocks param) - when it blocks it merely(!) needs to

wait for transactions to complete and be committed from other tasks,

so essentially we are waiting for jbd2_journal_stop(). So to avoid

deadlocks you must treat jbd2_journal_start/stop() as if they

were semaphores and include them in your semaphore ordering rules to prevent

deadlocks. Note that jbd2_journal_extend() has similar blocking behaviour to

jbd2_journal_start() so you can deadlock here just as easily as on

jbd2_journal_start().

</para>

<para>

Try to reserve the right number of blocks the first time. ;-). This will

be the maximum number of blocks you are going to touch in this transaction.

I advise having a look at at least ext4_jbd.h to see the basis on which

ext4 uses to make these decisions.

</para>

<para>

Another wriggle to watch out for is your on-disk block allocation strategy.

Why? Because, if you do a delete, you need to ensure you haven't reused any

of the freed blocks until the transaction freeing these blocks commits. If you

reused these blocks and crash happens, there is no way to restore the contents

of the reallocated blocks at the end of the last fully committed transaction.

One simple way of doing this is to mark blocks as free in internal in-memory

block allocation structures only after the transaction freeing them commits.

Ext4 uses journal commit callback for this purpose.

</para>

<para>

With journal commit callbacks you can ask the journalling layer to call a

callback function when the transaction is finally committed to disk, so that

you can do some of your own management. You ask the journalling layer for

calling the callback by simply setting journal->j_commit_callback function

pointer and that function is called after each transaction commit. You can also

use transaction->t_private_list for attaching entries to a transaction that

need processing when the transaction commits.

</para>

<para>

JBD2 also provides a way to block all transaction updates via

jbd2_journal_{un,}lock_updates(). Ext4 uses this when it wants a window with a

clean and stable fs for a moment.  E.g.

</para>

<programlisting>

	jbd2_journal_lock_updates() //stop new stuff happening..

	jbd2_journal_flush()        // checkpoint everything.

	..do stuff on stable fs

	jbd2_journal_unlock_updates() // carry on with filesystem use.

</programlisting>

<para>

The opportunities for abuse and DOS attacks with this should be obvious,

if you allow unprivileged userspace to trigger codepaths containing these

calls.

</para>

    </sect2>

    <sect2 id="jbd_summary">

     <title>Summary</title>

<para>

Using the journal is a matter of wrapping the different context changes,

being each mount, each modification (transaction) and each changed buffer

to tell the journalling layer about them.

</para>

    </sect2>

    </sect1>

    <sect1 id="data_types">

     <title>Data Types</title>

     <para>

	The journalling layer uses typedefs to 'hide' the concrete definitions

	of the structures used. As a client of the JBD2 layer you can

	just rely on the using the pointer as a magic cookie  of some sort.

	Obviously the hiding is not enforced as this is 'C'.

     </para>

	<sect2 id="structures"><title>Structures</title>

!Iinclude/linux/jbd2.h

	</sect2>

    </sect1>

    <sect1 id="functions">

     <title>Functions</title>

     <para>

	The functions here are split into two groups those that

	affect a journal as a whole, and those which are used to

	manage transactions

     </para>

	<sect2 id="journal_level"><title>Journal Level</title>

!Efs/jbd2/journal.c

!Ifs/jbd2/recovery.c

	</sect2>

	<sect2 id="transaction_level"><title>Transasction Level</title>

!Efs/jbd2/transaction.c

	</sect2>

    </sect1>

    <sect1 id="see_also">

     <title>See also</title>

	<para>

	  <citation>

	   <ulink url="http://kernel.org/pub/linux/kernel/people/sct/ext3/journal-design.ps.gz">

	   	Journaling the Linux ext2fs Filesystem, LinuxExpo 98, Stephen Tweedie

	   </ulink>

	  </citation>

	</para>

	<para>

	   <citation>

	   <ulink url="http://olstrans.sourceforge.net/release/OLS2000-ext3/OLS2000-ext3.html">

	   	Ext3 Journalling FileSystem, OLS 2000, Dr. Stephen Tweedie

	   </ulink>

	   </citation>

	</para>

    </sect1>

  </chapter>

  <chapter id="splice">

      <title>splice API</title>

  <para>

	splice is a method for moving blocks of data around inside the

	kernel, without continually transferring them between the kernel

	and user space.

  </para>

!Ffs/splice.c

  </chapter>

  <chapter id="pipes">

      <title>pipes API</title>

  <para>

	Pipe interfaces are all for in-kernel (builtin image) use.

	They are not exported for use by modules.

  </para>

!Iinclude/linux/pipe_fs_i.h

!Ffs/pipe.c

  </chapter>

</book>