diff options
| author | NeilBrown <neilb@suse.com> | 2017-03-15 14:05:14 +1100 |
|---|---|---|
| committer | Shaohua Li <shli@fb.com> | 2017-03-22 19:18:30 -0700 |
| commit | 55cc39f345256af241deb6152ff5c06bedd10f11 (patch) | |
| tree | 9d6958f5b6960b3ba9010aa0d23bbe9c3feb5ff2 | |
| parent | 6497709b5d1bccce7de1df678d5f147d614551d1 (diff) | |
md: close a race with setting mddev->in_sync
If ->in_sync is being set just as md_write_start() is being called,
it is possible that set_in_sync() won't see the elevated
->writes_pending, and md_write_start() won't see the set ->in_sync.
To close this race, re-test ->writes_pending after setting ->in_sync,
and add memory barriers to ensure the increment of ->writes_pending
will be seen by the time of this second test, or the new ->in_sync
will be seen by md_write_start().
Add a spinlock to array_state_show() to ensure this temporary
instability is never visible from userspace.
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
| -rw-r--r-- | drivers/md/md.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c index 5951dea75aba..dee6bbfb29b8 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -2258,6 +2258,10 @@ static bool set_in_sync(struct mddev *mddev) if (atomic_read(&mddev->writes_pending) == 0) { if (mddev->in_sync == 0) { mddev->in_sync = 1; + smp_mb(); + if (atomic_read(&mddev->writes_pending)) + /* lost a race with md_write_start() */ + mddev->in_sync = 0; set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags); sysfs_notify_dirent_safe(mddev->sysfs_state); } @@ -4011,6 +4015,7 @@ array_state_show(struct mddev *mddev, char *page) st = read_auto; break; case 0: + spin_lock(&mddev->lock); if (test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) st = write_pending; else if (mddev->in_sync) @@ -4019,6 +4024,7 @@ array_state_show(struct mddev *mddev, char *page) st = active_idle; else st = active; + spin_unlock(&mddev->lock); } else { if (list_empty(&mddev->disks) && @@ -7885,6 +7891,7 @@ void md_write_start(struct mddev *mddev, struct bio *bi) did_change = 1; } atomic_inc(&mddev->writes_pending); + smp_mb(); /* Match smp_mb in set_in_sync() */ if (mddev->safemode == 1) mddev->safemode = 0; if (mddev->in_sync) { |