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 > -- Andy Lutomirski AMA Capital Management, LLC -- 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
