* [PATCH] md: fix deadlock error in recent patch.
@ 2017-10-05 5:23 NeilBrown
2017-10-05 17:00 ` Shaohua Li
0 siblings, 1 reply; 2+ messages in thread
From: NeilBrown @ 2017-10-05 5:23 UTC (permalink / raw)
To: Shaohua Li; +Cc: Linux Raid, Xiao Ni
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A recent patch aimed to cause md_write_start() to fail (rather than
block) when the mddev was suspending, so as to avoid deadlocks.
Unfortunately the test in wait_event() was wrong, and it didn't change
behaviour at all.
We wait_event() must wait until the metadata is written OR the array is
suspending.
Fixes: cc27b0c78c79 ("md: fix deadlock between mddev_suspend() and md_write_start()")
Cc: stable@vger.kernel.org
Reported-by: Xiao Ni <xni@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
---
drivers/md/md.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 0ff1bbf6c90e..8b2eb0f4122f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8039,7 +8039,8 @@ bool md_write_start(struct mddev *mddev, struct bio *bi)
if (did_change)
sysfs_notify_dirent_safe(mddev->sysfs_state);
wait_event(mddev->sb_wait,
- !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) && !mddev->suspended);
+ !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) ||
+ mddev->suspended);
if (test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) {
percpu_ref_put(&mddev->writes_pending);
return false;
--
2.14.0.rc0.dirty
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^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] md: fix deadlock error in recent patch.
2017-10-05 5:23 [PATCH] md: fix deadlock error in recent patch NeilBrown
@ 2017-10-05 17:00 ` Shaohua Li
0 siblings, 0 replies; 2+ messages in thread
From: Shaohua Li @ 2017-10-05 17:00 UTC (permalink / raw)
To: NeilBrown; +Cc: Linux Raid, Xiao Ni
On Thu, Oct 05, 2017 at 04:23:16PM +1100, Neil Brown wrote:
>
> A recent patch aimed to cause md_write_start() to fail (rather than
> block) when the mddev was suspending, so as to avoid deadlocks.
> Unfortunately the test in wait_event() was wrong, and it didn't change
> behaviour at all.
>
> We wait_event() must wait until the metadata is written OR the array is
> suspending.
Ouch, probably suspended isn't set normally, so it doesn't get caught. Applied, thanks Neil and Xiao!
> Fixes: cc27b0c78c79 ("md: fix deadlock between mddev_suspend() and md_write_start()")
> Cc: stable@vger.kernel.org
> Reported-by: Xiao Ni <xni@redhat.com>
> Signed-off-by: NeilBrown <neilb@suse.com>
> ---
> drivers/md/md.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 0ff1bbf6c90e..8b2eb0f4122f 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8039,7 +8039,8 @@ bool md_write_start(struct mddev *mddev, struct bio *bi)
> if (did_change)
> sysfs_notify_dirent_safe(mddev->sysfs_state);
> wait_event(mddev->sb_wait,
> - !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) && !mddev->suspended);
> + !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) ||
> + mddev->suspended);
> if (test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) {
> percpu_ref_put(&mddev->writes_pending);
> return false;
> --
> 2.14.0.rc0.dirty
>
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2017-10-05 5:23 [PATCH] md: fix deadlock error in recent patch NeilBrown
2017-10-05 17:00 ` Shaohua Li
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