Hi! > commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream. > > commit d3374825ce57 ("md: make devices disappear when they are no longer > needed.") introduced protection between mddev creating & removing. The > md_open shouldn't create mddev when all_mddevs list doesn't contain > mddev. With currently code logic, there will be very easy to trigger > soft lockup in non-preempt env. > > This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which > will break the infinitely retry when md_open enter racing area. > > This patch is partly fix soft lockup issue, full fix needs mddev_find > is split into two functions: mddev_find & mddev_find_or_alloc. And > md_open should call new mddev_find (it only does searching job). > > For more detail, please refer with Christoph's "split mddev_find" patch > in later commits. Something went wrong here; changelog is truncated, in particular it does not contain required sign-offs. Best regards, Pavel > +++ b/drivers/md/md.c > @@ -7857,8 +7857,7 @@ static int md_open(struct block_device * > /* Wait until bdev->bd_disk is definitely gone */ > if (work_pending(&mddev->del_work)) > flush_workqueue(md_misc_wq); > - /* Then retry the open from the top */ > - return -ERESTARTSYS; > + return -EBUSY; > } > BUG_ON(mddev != bdev->bd_disk->private_data);
On Thu, May 13, 2021 at 11:47:15AM +0200, Greg Kroah-Hartman wrote: > On Thu, May 13, 2021 at 09:59:41AM +0200, Pavel Machek wrote: > > Hi! > > > > > commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream. > > > > > > commit d3374825ce57 ("md: make devices disappear when they are no longer > > > needed.") introduced protection between mddev creating & removing. The > > > md_open shouldn't create mddev when all_mddevs list doesn't contain > > > mddev. With currently code logic, there will be very easy to trigger > > > soft lockup in non-preempt env. > > > > > > This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which > > > will break the infinitely retry when md_open enter racing area. > > > > > > This patch is partly fix soft lockup issue, full fix needs mddev_find > > > is split into two functions: mddev_find & mddev_find_or_alloc. And > > > md_open should call new mddev_find (it only does searching job). > > > > > > For more detail, please refer with Christoph's "split mddev_find" patch > > > in later commits. > > > > Something went wrong here; changelog is truncated, in particular it > > does not contain required sign-offs. > > That's really odd, let me figure out what went wrong there, might be a > quilt thing... Yup, it's a bug in quilt, the header is just dropped for some reason. Will dig further, thanks for pointing this out. greg k-h
--- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7857,8 +7857,7 @@ static int md_open(struct block_device * /* Wait until bdev->bd_disk is definitely gone */ if (work_pending(&mddev->del_work)) flush_workqueue(md_misc_wq); - /* Then retry the open from the top */ - return -ERESTARTSYS; + return -EBUSY; } BUG_ON(mddev != bdev->bd_disk->private_data);
From: Zhao Heming <heming.zhao@suse.com> commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream. commit d3374825ce57 ("md: make devices disappear when they are no longer needed.") introduced protection between mddev creating & removing. The md_open shouldn't create mddev when all_mddevs list doesn't contain mddev. With currently code logic, there will be very easy to trigger soft lockup in non-preempt env. This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which will break the infinitely retry when md_open enter racing area. This patch is partly fix soft lockup issue, full fix needs mddev_find is split into two functions: mddev_find & mddev_find_or_alloc. And md_open should call new mddev_find (it only does searching job). For more detail, please refer with Christoph's "split mddev_find" patch in later commits. --- drivers/md/md.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)