Re: [PATCH v2] tmpfs.5: document size/blocks=0 and nr_inodes=0 <=> unlimited

[Alejandro Colomar <alx@kernel.org>]

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Hi,

On 2023-08-12 22:03, наб wrote:
> Bitten by this again. Behaviour blames back to at least 2005
> (probably original to shmem.c), documented upstream in
> Documentation/filesystems/tmpfs.rst (formerly .txt).
> 
> For example:
>   # mount -t tmpfs -o size=0 tmpfs /etc/
>   # df /etc/
>   Filesystem 1k-blocks Used Avail Use% Mounted on
>   tmpfs              0    0     0    - /etc
>   # head -c100M  < /dev/urandom > /etc/passwd
>   # df /etc/
>   Filesystem 1k-blocks Used Avail Use% Mounted on
>   tmpfs              0    0     0    - /etc
>   # ls -l /etc/passwd
>   -rw-r--r-- 1 0 0 104857600 08-12 19:55 /etc/passwd
>   # du /etc/passwd
>   204800  /etc/passwd
> whereas the current manual insinuates head should ENOSPC instantly.
> 
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>

Patch applied.  Thanks,

Alex

> ---
>  man5/tmpfs.5 | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/man5/tmpfs.5 b/man5/tmpfs.5
> index cdd5f2fd8..5274e632d 100644
> --- a/man5/tmpfs.5
> +++ b/man5/tmpfs.5
> @@ -51,6 +51,8 @@ .SS Mount options
>  .BR size "=\fIbytes\fP"
>  Specify an upper limit on the size of the filesystem.
>  The size is given in bytes, and rounded up to entire pages.
> +The limit is removed if the size is
> +.BR 0 .
>  .IP
>  The size may have a
>  .BR k ,
> @@ -89,6 +91,8 @@ .SS Mount options
>  The maximum number of inodes for this instance.
>  The default is half of the number of your physical RAM pages, or (on a
>  machine with highmem) the number of lowmem RAM pages, whichever is smaller.
> +The limit is removed if the number is
> +.BR 0 .
>  .IP
>  Inodes may be specified with
>  .BR k ,

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