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SubjectRe: [PATCH] Squashfs: Refactor decompressor interface and code
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On Tue, Oct 8, 2013 at 11:14 AM, Phillip Lougher
<phillip@squashfs.org.uk> wrote:
> 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
>
> This has the following functions
>
> decompressor_create()
> - Called at mount time to initialise internal decompressor state.
> - An opaque pointer to the decompressor private state is returned (or error).
> - The function is called with a pointer to the parsed and swapped comp_opts
> structure returned by the new decompressor comp_opts() call.
>
> decompressor_destroy()
> - Destroy all decompressor private state
> - kfree the comp_opts buffer
>
> decompress()
> - Select a decompressor or create a new decompressor
> - Call using whatever locking scheme is necessary
>
> All decompressor implementation specific private state has been moved from the
> squashfs_sb_info structure into the opaque private state returned by
> decompressor_create(). This is deliberate, now all implementation specific
> code has been moved to decompressor_xxx.c, no other code needs to/or should need
> to access anything within it.
>
> Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>

Reviewed-by: Minchan Kim <minchan@kernel.org>

It's a really fantastic clean up. I will implement
decompressor_multi.c after holiday.
Thanks for your help!

--
Kind regards,
Minchan Kim


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