This is a note to let you know that I've just added the patch titled
md: Close race when setting 'action' to 'idle'.
to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
md-close-race-when-setting-action-to-idle.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8e8e2518fceca407bb8fc2a6710d19d2e217892e Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Fri, 12 Jun 2015 19:51:27 +1000
Subject: md: Close race when setting 'action' to 'idle'.
From: NeilBrown <neilb@xxxxxxx>
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@xxxxxxx>
Fixes: 6791875e2e53 ("md: make reconfig_mutex optional for writes to md sysfs files.")
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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))
Patches currently in stable-queue which might be from neilb@xxxxxxx are
queue-4.0/md-close-race-when-setting-action-to-idle.patch
queue-4.0/md-don-t-return-0-from-array_state_store.patch
queue-4.0/block-fix-ext_dev_lock-lockdep-report.patch
queue-4.0/block-discard-bdi_unregister-in-favour-of-bdi_destroy.patch
queue-4.0/blk-mq-free-hctx-ctxs-in-queue-s-release-handler.patch
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