Further generalise the decompressors by adding a page handler
abstraction. This adds helpers to allow the decompressors
to access and process the output buffers in an implementation
independant manner.
This allows different types of output buffer to be passed
to the decompressors, with the implementation specific
aspects handled at decompression time, but without the
knowledge being held in the decompressor wrapper code.
This will allow the decompressors to handle Squashfs
cache buffers, and page cache pages.
This patch adds the abstraction and an implementation for
the caches.
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>
The decompressor interface and code was written from
the point of view of single-threaded operation. In doing
so it mixed a lot of single-threaded implementation specific
aspects into the decompressor code and elsewhere which makes it
difficult to seamlessly support multiple different decompressor
implementations.
This patch does the following:
1. It removes compressor_options parsing from the decompressor
init() function. This allows the decompressor init() function
to be dynamically called to instantiate multiple decompressors,
without the compressor options needing to be read and parsed each
time.
2. It moves threading and all sleeping operations out of the
decompressors. In doing so, it makes the decompressors
non-blocking wrappers which only deal with interfacing with
the decompressor implementation.
3. It splits decompressor.[ch] into decompressor generic functions
in decompressor.[ch], and moves the single threaded
decompressor implementation into decompressor_single.c.
The result of this patch is Squashfs should now be able to
support multiple decompressors by adding new decompressor_xxx.c
files with specialised implementations of the functions in
decompressor_single.c
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>
My existing email address may stop working in a month or two, so update
email to one that will continue working.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Pass the dictionary size used to compress datablocks. Using a
dictionary size less than the block size saves memory overhead, in many
cases without adversely affecting compression ratio.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Extend decompressor framework to handle compression options stored in
the filesystem. These options can be used by the relevant decompressor
at initialisation time to over-ride defaults.
The presence of compression options in the filesystem is indicated by
the COMP_OPT filesystem flag. If present the data is read from the
filesystem and passed to the decompressor init function. The decompressor
init function signature has been extended to take this data.
Also update the init function signature in the glib, lzo and xz
decompressor wrappers.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Fix potential use of uninitialised variable caused by recent
decompressor code optimisations.
In zlib_uncompress (zlib_wrapper.c) we have
int zlib_err, zlib_init = 0;
...
do {
...
if (avail == 0) {
offset = 0;
put_bh(bh[k++]);
continue;
}
...
zlib_err = zlib_inflate(stream, Z_SYNC_FLUSH);
...
} while (zlib_err == Z_OK);
If continue is executed (avail == 0) then the while condition will be
evaluated testing zlib_err, which is uninitialised first time around the
loop.
Fix this by getting rid of the 'if (avail == 0)' condition test, this
edge condition should not be being handled in the decompressor code, and
instead handle it generically in the caller code.
Similarly for xz_wrapper.c.
Incidentally, on most architectures (bar Mips and Parisc), no
uninitialised variable warning is generated by gcc, this is because the
while condition test on continue is optimised out and not performed
(when executing continue zlib_err has not been changed since entering
the loop, and logically if the while condition was true previously, then
it's still true).
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Reported-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add support for reading file systems compressed with the
XZ compression algorithm.
This patch adds the XZ decompressor wrapper code.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
