Hello Yang Xu,
On 9/9/20 2:05 PM, Yang Xu wrote:
> Signed-off-by: Yang Xu <xuyang2018.jy@xxxxxxxxxxxxxx>
> ---
> man4/loop.4 | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/man4/loop.4 b/man4/loop.4
> index f4cf48043..5cc9a7e79 100644
> --- a/man4/loop.4
> +++ b/man4/loop.4
> @@ -136,6 +136,14 @@ Allow automatic partition scanning.
> Use direct I/O mode to access the backing file.
> .RE
> .TP
> +The
> +.BR LOOP_SET_STATUS
> +can neither set the
> +.BR LO_FLAGS_READ_ONLY
> +nor
> +.BR LO_FLAGS_DIRECT_IO
> +lo_flags because they are exclusively set from kernel.
> +.TP
> .B LOOP_GET_STATUS
> Get the status of the loop device.
> The (third)
Looking at the kernel code:
[[
> /* LO_FLAGS that can be set using LOOP_SET_STATUS(64) */
#define LOOP_SET_STATUS_SETTABLE_FLAGS (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN)
/* LO_FLAGS that can be cleared using LOOP_SET_STATUS(64) */
#define LOOP_SET_STATUS_CLEARABLE_FLAGS (LO_FLAGS_AUTOCLEAR)
/* LO_FLAGS that can be set using LOOP_CONFIGURE */
#define LOOP_CONFIGURE_SETTABLE_FLAGS (LO_FLAGS_READ_ONLY | LO_FLAGS_AUTOCLEAR \
| LO_FLAGS_PARTSCAN | LO_FLAGS_DIRECT_IO)
]]
and
[[
/* Mask out flags that can't be set using LOOP_SET_STATUS. */
lo->lo_flags &= LOOP_SET_STATUS_SETTABLE_FLAGS;
/* For those flags, use the previous values instead */
lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_SETTABLE_FLAGS;
/* For flags that can't be cleared, use previous values too */
lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_CLEARABLE_FLAGS;
]]
would it not be clearer and simpler just to say something like:
[[
The only lo_flags that can be modified using LOOP_SET_STATUS are
LO_FLAGS_AUTOCLEAR and LO_FLAGS_PARTSCAN.
]]
?
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
