lkml.org 
[lkml]   [2017]   [May]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH] mount.2: revise description of MS_REMOUNT | MS_BIND

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>
---
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
--
2.12.2
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2017-05-19 08:57    [W:0.042 / U:4.036 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site