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.
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
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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