linux-kernel - Re: [PATCH v2] docs: filesystems: document the squashfs specific mount options

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Date:   Mon, 30 Oct 2023 14:57:00 +0200
From:   Ariel Miculas <amiculas@...co.com>
To:     Phillip Lougher <phillip@...ashfs.org.uk>
Cc:     linux-doc@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>, serge@...lyn.com,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] docs: filesystems: document the squashfs specific
 mount options

On 23/10/29 08:33PM, Phillip Lougher wrote:
> On 29/10/2023 16:19, Ariel Miculas wrote:
> > When SQUASHFS_CHOICE_DECOMP_BY_MOUNT is set, the "threads" mount option
> > can be used to specify the decompression mode: single-threaded,
> > multi-threaded, percpu or the number of threads used for decompression.
> > When SQUASHFS_CHOICE_DECOMP_BY_MOUNT is not set and
> > SQUASHFS_DECOMP_MULTI is set, the "threads" option can also be used to
> > specify the number of threads used for decompression. This mount option
> > is only mentioned in fs/squashfs/Kconfig, which makes it difficult to
> > find.
> > 
> > Another mount option available is "errors", which can be configured to
> > panic the kernel when squashfs errors are encountered.
> > 
> > Add both these options to the squashfs documentation, making them more
> > noticeable.
> > 
> > Signed-off-by: Ariel Miculas <amiculas@...co.com>
> 
> Looks good to me.
> 
> Reviewed-by: Phillip Lougher <phillip@...ashfs.org.uk>

Unfortunately, it seems this is not quite correct either:
There is the config option SQUASHFS_MOUNT_DECOMP_THREADS:
```
	bool "Add the mount parameter 'threads=' for squashfs"
	depends on SQUASHFS
	depends on SQUASHFS_DECOMP_MULTI
	default n
	help
	  Use threads= to set the decompression parallel mode and the number of threads.
	  If SQUASHFS_CHOICE_DECOMP_BY_MOUNT=y
	      threads=<single|multi|percpu|1|2|3|...>
	  else
	      threads=<2|3|...>
	  The upper limit is num_online_cpus() * 2.
```
that depends on SQUASHFS_DECOMP_MULTI.
So I think I should take my v1 patch and specify that the "threads="
mount option depends on SQUASHFS_MOUNT_DECOMP_THREADS. There's no need
to specify SQUASHFS_DECOMP_MULTI, because SQUASHFS_MOUNT_DECOMP_THREADS
already depends on it.
What do you think?

Regards,
Ariel