lkml.org 
[lkml]   [2015]   [Jun]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.0 091/105] md: Close race when setting action to idle.
Date
4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

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))

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2015-06-19 23:01    [W:0.942 / U:0.284 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site