On Sat, Apr 14, 2018 at 12:00:13AM +0200, Martin Wilck wrote:
> For "find_multipaths smart", check if a path is already in use
> before setting DM_MULTIPATH_DEVICE_PATH to 1 or 2 (and thus,
> SYSTEMD_READY=0). If we don't do this, a device which has already been
> mounted (e.g. during initrd processing) may be unmounted by systemd, causing
> havoc to the boot process.
>
Reviewed-by: Benjamin Marzinsk <bmarz...@redhat.com>
> Signed-off-by: Martin Wilck <mwi...@suse.com>
> ---
> multipath/main.c | 39 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/multipath/main.c b/multipath/main.c
> index 573d94f9..c69e996e 100644
> --- a/multipath/main.c
> +++ b/multipath/main.c
> @@ -675,6 +675,9 @@ configure (struct config *conf, enum mpath_cmds cmd,
>
>
> if (cmd == CMD_VALID_PATH) {
> + struct path *pp;
> + int fd;
> +
> /* This only happens if find_multipaths and
> * ignore_wwids is set, and the path is not in WWIDs
> * file, not currently multipathed, and has
> @@ -682,11 +685,45 @@ configure (struct config *conf, enum mpath_cmds cmd,
> * If there is currently a multipath device matching
> * the refwwid, or there is more than one path matching
> * the refwwid, then the path is valid */
> - if (VECTOR_SIZE(curmp) != 0 || VECTOR_SIZE(pathvec) > 1)
> + if (VECTOR_SIZE(curmp) != 0) {
> + r = 0;
> + goto print_valid;
> + } else if (VECTOR_SIZE(pathvec) > 1)
> r = 0;
> else
> /* Use r=2 as an indication for "maybe" */
> r = 2;
> +
> + /*
> + * If opening the path with O_EXCL fails, the path
> + * is in use (e.g. mounted during initramfs processing).
> + * We know that it's not used by dm-multipath.
> + * We may not set SYSTEMD_READY=0 on such devices, it
> + * might cause systemd to umount the device.
> + * Use O_RDONLY, because udevd would trigger another
> + * uevent for close-after-write.
> + *
> + * The O_EXCL check is potentially dangerous, because it may
> + * race with other tasks trying to access the device. Therefore
> + * this code is only executed if the path hasn't been released
> + * to systemd earlier (see above).
> + *
> + * get_refwwid() above stores the path we examine in slot 0.
> + */
> + pp = VECTOR_SLOT(pathvec, 0);
> + fd = open(udev_device_get_devnode(pp->udev),
> + O_RDONLY|O_EXCL);
> + if (fd >= 0)
> + close(fd);
> + else {
> + condlog(3, "%s: path %s is in use: %s",
> + __func__, pp->dev,
> + strerror(errno));
> + /*
> + * Check if we raced with multipathd
> + */
> + r = !sysfs_is_multipathed(VECTOR_SLOT(pathvec, 0));
> + }
> goto print_valid;
> }
>
> --
> 2.16.1
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