[Crash-utility] [RFC] makedumpfile, crash: LZO compression support

[Dave Anderson]

----- Original Message -----
> Hello,
> 
> This is a RFC patch set that adds LZO compression support to
> makedumpfile and crash utility. LZO is as good as in size but by far
> better in speed than ZLIB, leading to reducing down time during
> generation of crash dump and refiltering.
> 
> How to build:
> 
>   1. Get LZO library, which is provided as lzo-devel package on recent
>   linux distributions, and is also available on author's website:
>   http://www.oberhumer.com/opensource/lzo/.
> 
>   2. Apply the patch set to makedumpfile v1.4.0 and crash v6.0.0.
> 
>   3. Build both using make. But for crash, do the following now:
> 
>     $ make CFLAGS="-llzo2"
> 
> How to use:
> 
>   I've newly used -l option for lzo compression in this patch. So for
>   example, do as follows:
> 
>   $ makedumpfile -l vmcore dumpfile
>   $ crash vmlinux dumpfile
> 
> Request of configure-like feature for crash utility:
> 
>   I would like configure-like feature on crash utility for users to
>   select wheather to add LZO feature actually or not in build-time,
>   that is: ./configure --enable-lzo or ./configure --disable-lzo.
> 
>   The reason is that support staff often downloads and installs the
>   latest version of crash utility on machines where lzo library is not
>   provided.

Right, at least on Fedora, these three packages would need to be installed:

 lzo-2.06-1.fc15.x86_64
 lzo-minilzo-2.06-1.fc15.x86_64
 lzo-devel-2.06-1.fc15.x86_64

> 
>   Looking at the source code, it looks to me that crash does some kind
>   of configuration processing in a local manner, around configure.c,
>   and I guess it's difficult to use autoconf tools directly.
> 
>   Or is there another better way?

Instead of using CFLAGS, it would be preferable to dynamically append "-llzo2" to 
the string that the gdb_merge stanza in the Makefile writes to the "mergelibs"
file here:

gdb_merge: force
        @if [ ! -f ${GDB}/README ]; then \
          make --no-print-directory gdb_unzip; fi
===>    @echo "${LDFLAGS} -lz -ldl -rdynamic" > ${GDB}/gdb/mergelibs
        @echo "../../${PROGRAM} ../../${PROGRAM}lib.a" > ${GDB}/gdb/mergeobj
        @if [ ! -f ${GDB}/config.status ]; then \
          (cd ${GDB}; ./configure ${GDB_CONF_FLAGS} --with-separate-debug-dir=/usr/lib/debug \
            --with-bugurl="" --with-expat=no --with-python=no; \
          make --no-print-directory; echo ${TARGET} > crash.target) \
        else (cd ${GDB}/gdb; make --no-print-directory;); fi
        @if [ ! -f ${GDB}/gdb/libgdb.a ]; then \
          echo; echo "gdb build failed: ${GDB}/gdb/libgdb.a does not exist"; \
          echo; exit 1; fi

It also requires an additional #define so that the #include line in defs.h
and the calls to lzo_init() and lzo1x_decompress_safe() in diskdump.c can 
be encapsulated, i.e., something like:

#ifdef LZO 
#include <lzo/lzo1x.h>
#endif

#ifdef LZO
        dd->lzo_supported = lzo_init() == LZO_E_OK;
#endif

#ifdef LZO
                ret = lzo1x_decompress_safe(dd->compressed_page, pd.size,
                                            dd->page_cache_hdr[i].pg_bufptr,
                                            &retlen, LZO1X_MEM_DECOMPRESS);
#endif

The -DLZO would only need to be passed to the diskump.c compile line.

This could involve configure.c, but conceivably it could all be done within the 
Makefile itself.  For example, by entering something like "make compress=lzo2", 
and then adding this to the Makefile:

ifneq ($(compress),)
ifeq ($(compress), lzo2)
  LZOFLAG=-DLZO
  LZOLIB=-llzo2
endif
endif

And then the diskdump.c compile line could use ${LZOFLAG}, and the
gdb_merge stanza could include ${LZOLIB}.

Thanks,
  Dave