[PATCH] md: move revalidate_disk() back outside open_mutex

[PATCH] md: move revalidate_disk() back outside open_mutex

[Dan Williams]

Commit b821eaa5 "md: remove ->changed and related code" moved
revalidate_disk() under open_mutex, and lockdep noticed.

[ INFO: possible circular locking dependency detected ]
2.6.32-mdadm-locking #1
-------------------------------------------------------
mdadm/3640 is trying to acquire lock:
 (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811acecb>] revalidate_disk+0x5b/0x90

but task is already holding lock:
 (&mddev->open_mutex){+.+...}, at: [<ffffffffa055e07a>] do_md_stop+0x4a/0x4d0 [md_mod]

which lock already depends on the new lock.

Cc: <stable@kernel.org>
Reported-by: Przemyslaw Czarnowski <przemyslaw.hawrylewicz.czarnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/md/md.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index cb20d0b..9743554 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4711,7 +4711,7 @@ out:
  */
 static int do_md_stop(mddev_t * mddev, int mode, int is_open)
 {
-	int err = 0;
+	int err = 0, revalidate = 0;
 	struct gendisk *disk = mddev->gendisk;
 	mdk_rdev_t *rdev;
 
@@ -4740,7 +4740,7 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
 			}
 
 		set_capacity(disk, 0);
-		revalidate_disk(disk);
+		revalidate = 1;
 
 		if (mddev->ro)
 			mddev->ro = 0;
@@ -4748,6 +4748,8 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
 		err = 0;
 	}
 	mutex_unlock(&mddev->open_mutex);
+	if (revalidate)
+		revalidate_disk(disk);
 	if (err)
 		return err;
 	/*

Re: [PATCH] md: move revalidate_disk() back outside open_mutex

[Neil Brown]

On Fri, 06 Aug 2010 18:01:59 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> Commit b821eaa5 "md: remove ->changed and related code" moved
> revalidate_disk() under open_mutex, and lockdep noticed.
> 
> [ INFO: possible circular locking dependency detected ]
> 2.6.32-mdadm-locking #1
> -------------------------------------------------------
> mdadm/3640 is trying to acquire lock:
>  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811acecb>] revalidate_disk+0x5b/0x90
> 
> but task is already holding lock:
>  (&mddev->open_mutex){+.+...}, at: [<ffffffffa055e07a>] do_md_stop+0x4a/0x4d0 [md_mod]
> 
> which lock already depends on the new lock.

Thanks!  applied and sent to Linus - as you might have noticed.

I didn't really like the 'revalidate' variable, and realised that the 'err'
variable wasn't really needed either so added a patch to restructure the
function a little bit.

Thanks,
NeilBrown


> 
> Cc: <stable@kernel.org>
> Reported-by: Przemyslaw Czarnowski <przemyslaw.hawrylewicz.czarnowski@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/md/md.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index cb20d0b..9743554 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4711,7 +4711,7 @@ out:
>   */
>  static int do_md_stop(mddev_t * mddev, int mode, int is_open)
>  {
> -	int err = 0;
> +	int err = 0, revalidate = 0;
>  	struct gendisk *disk = mddev->gendisk;
>  	mdk_rdev_t *rdev;
>  
> @@ -4740,7 +4740,7 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
>  			}
>  
>  		set_capacity(disk, 0);
> -		revalidate_disk(disk);
> +		revalidate = 1;
>  
>  		if (mddev->ro)
>  			mddev->ro = 0;
> @@ -4748,6 +4748,8 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
>  		err = 0;
>  	}
>  	mutex_unlock(&mddev->open_mutex);
> +	if (revalidate)
> +		revalidate_disk(disk);
>  	if (err)
>  		return err;
>  	/*
> 
> --
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