| From 8e8e2518fceca407bb8fc2a6710d19d2e217892e Mon Sep 17 00:00:00 2001 |
| From: NeilBrown <neilb@suse.de> |
| Date: Fri, 12 Jun 2015 19:51:27 +1000 |
| Subject: md: Close race when setting 'action' to 'idle'. |
| |
| From: NeilBrown <neilb@suse.de> |
| |
| commit 8e8e2518fceca407bb8fc2a6710d19d2e217892e upstream. |
| |
| Checking ->sync_thread without holding the mddev_lock() |
| isn't really safe, even after flushing the workqueue which |
| ensures md_start_sync() has been run. |
| |
| While this code is waiting for the lock, md_check_recovery could reap |
| the thread itself, and then start another thread (e.g. recovery might |
| finish, then reshape starts). When this thread gets the lock |
| md_start_sync() hasn't run so it doesn't get reaped, but |
| MD_RECOVERY_RUNNING gets cleared. This allows two threads to start |
| which leads to confusion. |
| |
| So don't both if MD_RECOVERY_RUNNING isn't set, but if it is do |
| the flush and the test and the reap all under the mddev_lock to |
| avoid any race with md_check_recovery. |
| |
| Signed-off-by: NeilBrown <neilb@suse.de> |
| Fixes: 6791875e2e53 ("md: make reconfig_mutex optional for writes to md sysfs files.") |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/md/md.c | 11 ++++++----- |
| 1 file changed, 6 insertions(+), 5 deletions(-) |
| |
| --- a/drivers/md/md.c |
| +++ b/drivers/md/md.c |
| @@ -4144,13 +4144,14 @@ action_store(struct mddev *mddev, const |
| set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); |
| else |
| clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); |
| - flush_workqueue(md_misc_wq); |
| - if (mddev->sync_thread) { |
| - set_bit(MD_RECOVERY_INTR, &mddev->recovery); |
| - if (mddev_lock(mddev) == 0) { |
| + if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) && |
| + mddev_lock(mddev) == 0) { |
| + flush_workqueue(md_misc_wq); |
| + if (mddev->sync_thread) { |
| + set_bit(MD_RECOVERY_INTR, &mddev->recovery); |
| md_reap_sync_thread(mddev); |
| - mddev_unlock(mddev); |
| } |
| + mddev_unlock(mddev); |
| } |
| } else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) || |
| test_bit(MD_RECOVERY_NEEDED, &mddev->recovery)) |
