New subject: Timestamps from the future (was: [PATCH 5.10] md: Flush workqueue md_rdev_misc_wq in md_alloc())

24 Feb 2023

From: David Sloan david.sloan@eideticom.com
commit 5e8daf906f890560df430d30617c692a794acb73 upstream.
A race condition still exists when removing and re-creating md devices
in test cases. However, it is only seen on some setups.
The race condition was tracked down to a reference still being held
to the kobject by the rdev in the md_rdev_misc_wq which will be released
in rdev_delayed_delete().
md_alloc() waits for previous deletions by waiting on the md_misc_wq,
but the md_rdev_misc_wq may still be holding a reference to a recently
removed device.
To fix this, also flush the md_rdev_misc_wq in md_alloc().
Signed-off-by: David Sloan david.sloan@eideticom.com
[logang@deltatee.com: rewrote commit message]
Signed-off-by: Logan Gunthorpe logang@deltatee.com
Signed-off-by: Song Liu song@kernel.org
Signed-off-by: Hou Tao houtao1@huawei.com
---
Hi Greg,
We found the problem also exists on v5.10, so could you please pick it up
for v5.10 ?
Thanks.
drivers/md/md.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3038e7ecb7e1..c0b34637bd66 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5683,6 +5683,7 @@ static int md_alloc(dev_t dev, char *name)
     * completely removed (mddev_delayed_delete).
     */
    flush_workqueue(md_misc_wq);
+	flush_workqueue(md_rdev_misc_wq);
mutex_lock(&disks_mutex);
    error = -EEXIST;
-- 
2.29.2


    