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SubjectRe: [PATCH] mount.2: revise description of MS_REMOUNT | MS_BIND
Date
On 05/19/2017 08:55 AM, NeilBrown wrote:
>
> MS_REMOUNT|MS_BIND affect all per-mount-point
> flag. MS_READONLY is only special because it,
> uniquely, is both a per-mount-point flag *and* a
> per-filesystem flag.
>
> So the sections of per-mount-point flags and
> MS_REMOUNT can usefully be clarified.
>
> Signed-off-by: NeilBrown <neilb@suse.com>

Thanks, Neil. Applied.

Cheers,

Michael

> ---
> man2/mount.2 | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/man2/mount.2 b/man2/mount.2
> index 35fdda084d61..3e5348368757 100644
> --- a/man2/mount.2
> +++ b/man2/mount.2
> @@ -288,6 +288,12 @@ are also settable on a per-mount-point basis.
> The
> .B MS_RELATIME
> flag is also settable on a per-mount-point basis.
> +Since Linux 2.6.16,
> +.B MS_RDONLY
> +can be set or cleared on a per-mount-point basis as well as on
> +the underlying filesystem. The mounted filesystem will only be
> +writable if neither the filesystem nor the mountpoint are flagged as
> +read-only.
> .\"
> .SS Remounting an existing mount
> An existing mount may be remounted by specifying
> @@ -317,6 +323,10 @@ and
> arguments should match the values used in the original
> .BR mount ()
> call, except for those parameters that are being deliberately changed.
> +Another exception is that
> +.B MS_BIND
> +has a different meaning for remount, and it should only be included if
> +explicitly desired.
>
> The following
> .I mountflags
> @@ -351,17 +361,20 @@ then the remount operation preserves the existing values of these flags
> (rather than defaulting to
> .BR MS_RELATIME ).
>
> -Since Linux 2.6.26, this flag can also be used to make
> +Since Linux 2.6.26, this flag can be used with
> +.B MS_BIND
> +to only modify the per-mount-point flags.
> .\" See https://lwn.net/Articles/281157/
> -an existing bind mount read-only by specifying
> +This is particularly useful for setting or clearing the "read-only"
> +flag on a mount point without changing the underlying filesystem.
> +Specifying
> .IR mountflags
> as:
>
> MS_REMOUNT | MS_BIND | MS_RDONLY
>
> -Note that only the
> -.BR MS_RDONLY
> -setting of the bind mount can be changed in this manner.
> +will make access through this mountpoint read-only, without affecting
> +other mount points.
> .\"
> .SS Creating a bind mount
> If
>


--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

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