[PATCH 2/2] fs/squashfs: add support for ZSTD decompression

[Joao Marcos Costa]

On Tue, 11 Aug 2020 15:29:51 +0200
Thomas Petazzoni <thomas.petazzoni at bootlin.com> wrote:

> On Tue, 11 Aug 2020 15:17:55 +0200
> Joao Marcos Costa <joaomarcos.costa at bootlin.com> wrote:
> 
> > +#if IS_ENABLED(CONFIG_ZSTD)
> > +static int sqfs_zstd_decompress(void *dest, unsigned long dest_len,
> > +				void *source, u32 src_len)
> > +{
> > +	void *workspace;
> > +	ZSTD_DCtx *ctx;
> > +	size_t wsize;
> > +	int ret;
> > +
> > +	wsize = ZSTD_DCtxWorkspaceBound();  
> 
> So apparently this "workspace" has a constant size, which does not
> depend on the size of the input buffer. Correct ?

Yes, correct.

> If that's the case, can we instead allocate it once for all in
> sqfs_probe() if the filesystem is zstd-compressed ? I.e perhaps
> sqfs_probe() could call a sqfs_decompressor_init() function,
> implemented in sqfs_decompressor.c, which will do this sort of
> initialization. And of course this memory area would be freed up in
> sqfs_close(), calling a sqfs_decompressor_{deinit,cleanup,close}
> function.

Sure, it can be done. I will prepare a v2 addressing your suggestion.
Thanks!

> Best regards,
> 
> Thomas

Best regards,
Joao