md: rcu_read_lock() walk of mddev->disks in md_do_sync()

Other walks of this list are either under rcu_read_lock() or the list
mutation lock (mddev_lock()).  This protects against the improbable case of a
disk being removed from the array at the start of md_do_sync().

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

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 68a8a29..ea64a68 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6526,12 +6526,14 @@ void md_do_sync(mddev_t *mddev)
                /* recovery follows the physical size of devices */
                max_sectors = mddev->dev_sectors;
                j = MaxSector;
-               list_for_each_entry(rdev, &mddev->disks, same_set)
+               rcu_read_lock();
+               list_for_each_entry_rcu(rdev, &mddev->disks, same_set)
                        if (rdev->raid_disk >= 0 &&
                            !test_bit(Faulty, &rdev->flags) &&
                            !test_bit(In_sync, &rdev->flags) &&
                            rdev->recovery_offset < j)
                                j = rdev->recovery_offset;
+               rcu_read_unlock();
        }
 
        printk(KERN_INFO "md: %s of RAID array %s\n", desc, mdname(mddev));
@@ -6701,12 +6703,14 @@ void md_do_sync(mddev_t *mddev)
                } else {
                        if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery))
                                mddev->curr_resync = MaxSector;
-                       list_for_each_entry(rdev, &mddev->disks, same_set)
+                       rcu_read_lock();
+                       list_for_each_entry_rcu(rdev, &mddev->disks, same_set)
                                if (rdev->raid_disk >= 0 &&
                                    !test_bit(Faulty, &rdev->flags) &&
                                    !test_bit(In_sync, &rdev->flags) &&
                                    rdev->recovery_offset < mddev->curr_resync)
                                        rdev->recovery_offset = mddev->curr_resync;
+                       rcu_read_unlock();
                }
        }
        set_bit(MD_CHANGE_DEVS, &mddev->flags);