Hi Eric, I'm still hoping for a revised patch from you in the light of Andy's comments and question. Thanks, Michael On 09/30/2014 04:16 AM, Andy Lutomirski wrote: > On Mon, Sep 29, 2014 at 7:15 PM, Eric W. Biederman > <ebiederm@xxxxxxxxxxxx> wrote: >> Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes: >> >>> On Mon, Sep 29, 2014 at 6:04 PM, Eric W. Biederman >>> <ebiederm@xxxxxxxxxxxx> wrote: >>>> >>>> I recently realized that I had been reasoning improperly about what >>>> umount(MNT_DETACH) did based on an insufficient description in >>>> the umount.2 man page, that matched my intuition but not the >>>> implementation. >>>> >>>> When there are no submounts MNT_DETACH is essentially harmless to >>>> applications. Where there are submounts MNT_DETACH changes what >>>> is visible to applications using the detach directories. >>>> >>>> Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> >>>> --- >>>> man2/umount.2 | 7 ++++--- >>>> 1 file changed, 4 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/man2/umount.2 b/man2/umount.2 >>>> index 5ff88152c738..aea39d8306fe 100644 >>>> --- a/man2/umount.2 >>>> +++ b/man2/umount.2 >>>> @@ -66,9 +66,10 @@ This can cause data loss. >>>> (Only for NFS mounts.) >>>> .TP >>>> .BR MNT_DETACH " (since Linux 2.4.11)" >>>> -Perform a lazy unmount: make the mount point unavailable for >>>> -new accesses, and actually perform the unmount when the mount point >>>> -ceases to be busy. >>>> +Perform a lazy unmount: make the mount point unavailable for new >>>> +accesses, immediately disconnect the filesystem and all filesystems >>>> +mounted below it from each other and from the mount table, and >>>> +actually perform the unmount when the mount point ceases to be busy. >>> >>> Want to add something like: >>> >>> MNT_DETACH on a shared mount will propagate unmount events to its peer >>> group. That means that recursively bind mounting a shared mount and >>> then unmounting that recursive bind mount will unmount all submounts >>> of the original mount. This behavior can be avoided by remounting a >>> directory with MS_REC | MS_PRIVATE before unmounting it. >> >> Make that any unmount on a shared mount that will propogate unmount >> events to it's peer group. > > I don't understand your proposed edit. Can you type it out explicitly? > > --Andy > >> >> Eric >> > > > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
