Remove: container should wait for an array to release a drive

A 'faulty' drive is being removed from a container after it has been
released by an array, however there is a race there. The drive is
released asynchronously by a monitor but sometimes it doesn't happen
before container checks it. It results in a container refusing to remove
a drive as it still seems to be a part of some array.

It seems 'ping_monitor' could be a solution here to assure monitor has
had a chance to process the events, however it doesn't resolve the
problem - sometimes an array has to request a release of the drive few
times (as the array is busy) and single 'ping_monitor' call is not
sufficient. As there is no way to query monitor progress, it forces us
to retry a check several times before an error is returned.

Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>

diff --git a/Manage.c b/Manage.c
index 30adc993c46680502428c16ad1061c554736f6f1..1b7b0c111c837a01e084114840d4969d54601121 100644 (file)
--- a/Manage.c
+++ b/Manage.c
@@ -1125,19 +1125,34 @@ int Manage_remove(struct supertype *tst, int fd, struct mddev_dev *dv,
                 */
                if (rdev == 0)
                        ret = -1;
-               else
-                       ret = sysfs_unique_holder(devnm, rdev);
-               if (ret == 0) {
-                       pr_err("%s is not a member, cannot remove.\n",
-                              dv->devname);
-                       close(lfd);
-                       return -1;
-               }
-               if (ret >= 2) {
-                       pr_err("%s is still in use, cannot remove.\n",
-                              dv->devname);
-                       close(lfd);
-                       return -1;
+               else {
+                       /*
+                        * The drive has already been set to 'faulty', however
+                        * monitor might not have had time to process it and the
+                        * drive might still have an entry in the 'holders'
+                        * directory. Try a few times to avoid a false error
+                        */
+                       int count = 20;
+
+                       do {
+                               ret = sysfs_unique_holder(devnm, rdev);
+                               if (ret < 2)
+                                       break;
+                               usleep(100 * 1000);     /* 100ms */
+                       } while (--count > 0);
+
+                       if (ret == 0) {
+                               pr_err("%s is not a member, cannot remove.\n",
+                                       dv->devname);
+                               close(lfd);
+                               return -1;
+                       }
+                       if (ret >= 2) {
+                               pr_err("%s is still in use, cannot remove.\n",
+                                       dv->devname);
+                               close(lfd);
+                               return -1;
+                       }
                }
        }
        /* FIXME check that it is a current member */