Re: [PATCH v3] mount_setattr.2: New manual page documenting the mount_setattr() system call

["Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>]

Hi Christian,

This time I'm going to point out issues about the contents only, not 
groff fixes nor even punctuation fixes.  I'll fix those myself and CC 
you when I do that.

However, if you render the page yourself (man ./mount_setattr.2), you 
will probably notice some formatting issues.

Please see some comments below.

Thanks,

Alex

On 7/31/21 12:15 PM, Christian Brauner wrote:
> 
> +.SH ERRORS
> +.TP
> +.B EBADF
> +.I dfd
> +is not a valid file descriptor.
> +.TP
> +.B EBADF
> +An invalid file descriptor value was specified in
> +.I userns_fd.

Why a different wording compared to the above?  Aren't they the same?

userns_fd is not a valid descriptor.

That would be consistent with the first EBADF, and would keep the 
meaning, right?

> +.TP
> +.B EBUSY
> +The caller tried to change the mount to
> +.BR MOUNT_ATTR_RDONLY
> +but the mount had writers.

This is not so clear.  I think I understood it, but maybe using language 
similar to that of mount(2) is clearer:

EBUSY  source cannot be remounted read‐only, because it still holds 
files open for writing.

Something like?:

The caller tried to change the mount to MOUNT_ATTR_ONLY but the mount 
still has files open for writing


> 
> +static const struct option longopts[] = {
> +    {"map-mount",       required_argument,  0,  'a'},
> +    {"recursive",       no_argument,        0,  'b'},
> +    {"read-only",       no_argument,        0,  'c'},
> +    {"block-setid",     no_argument,        0,  'd'},
> +    {"block-devices",   no_argument,        0,  'e'},
> +    {"block-exec",      no_argument,        0,  'f'},
> +    {"no-access-time",  no_argument,        0,  'g'},
> +    { NULL,             0,                  0,   0 },
> +};

The third field is an 'int *' 
(https://www.gnu.org/software/libc/manual/html_node/Getopt-Long-Options.html). 
  Please, use NULL instead of 0.


> 
> +    struct mount_attr *attr = &(struct mount_attr){};

Wow!  Interesting usage of compound literals.
I had to check that this has automatic storage duration (I would have 
said that it has static s.d., but no).

I'm curious: why use that instead of just?:

struct mount_attr attr = {0};

> 
> +    if (ret < 0)
> +        exit_log("%m - Failed to change mount attributes\en");


Although I typically use myself that same < 0 check,
manual pages typically use == -1 when a function returns -1 on error 
(which most syscalls do), and Michael prefers that.



-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/