ping_manager() to prevent 'add' before 'remove' completes

It is currently possible to remove a device and re-add it without the
manager noticing, i.e. without detecting a mdstat->devcnt
container->devcnt mismatch.  Introduce ping_manager() to arrange for
mdmon to run manage_container() prior to mdadm dropping the exclusive
open() on the container.  Despite these precautions sysfs_read() may
still fail.  If this happens invalidate container->devcnt to ensure
manage_container() runs at the next event.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/Manage.c b/Manage.c
index 76447eda..5853515d 100644
--- a/Manage.c
+++ b/Manage.c
@@ -712,6 +712,23 @@ int Manage_subdevs(char *devname, int fd,
 					close(lfd);
 				return 1;
 			}
+			if (tst->ss->external) {
+				/*
+				 * Before dropping our exclusive open we make an
+				 * attempt at preventing mdmon from seeing an
+				 * 'add' event before reconciling this 'remove'
+				 * event.
+				 */
+				char *name = devnum2devname(fd2devnum(fd));
+
+				if (!name) {
+					fprintf(stderr, Name ": unable to get container name\n");
+					return 1;
+				}
+
+				ping_manager(name);
+				free(name);
+			}
 			close(lfd);
 			if (verbose >= 0)
 				fprintf(stderr, Name ": hot removed %s\n",