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. Eric -- 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
