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From: Greg KH on 11 Aug 2010 20:20
2.6.35-stable review patch. If anyone has any objections, please let us know.

------------------

From: Dan Williams <dan.j.williams(a)intel.com>

commit 147e0b6a639ac581ca3bf627bedc3f4a6d3eca66 upstream.

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.

It is suitable for 2.6.35.x

Reported-by: Przemyslaw Czarnowski <przemyslaw.hawrylewicz.czarnowski(a)intel.com>
Signed-off-by: Dan Williams <dan.j.williams(a)intel.com>
Signed-off-by: NeilBrown <neilb(a)suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
drivers/md/md.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- 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, i
}

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, i
err = 0;
}
mutex_unlock(&mddev->open_mutex);
+ if (revalidate)
+ revalidate_disk(disk);
if (err)
return err;
/*


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