Re: [PATCH v2] Btrfs, lockdep: get_restripe_target: use lockdep in BUG_ON

[Bobby Powers <bobbypowers@gmail.com>]

On Wed, Apr 4, 2012 at 10:04 PM, Bobby Powers <bobbypowers@gmail.com> w=
rote:
> spin_is_locked always returns 0 on non-SMP systems, which causes btrf=
s
> to fail the mount. =A0There is documentation pending as to why checki=
ng

I guess I should be explicit in stating that this is a regression, so
this patch or something else that addresses it should be pulled into
3.4.

> for spin_is_locked is a bad idea:
>
> https://lkml.org/lkml/2012/3/27/413
>
> The suggested lockdep_assert_held() is not appropriate in this case,
> as what get_restripe_target() is checking for is that either
> volume_mutex is held or balance_lock is held. =A0Luckily
> lockdep_assert_held() is a simple macro:
>
> WARN_ON(debug_locks && !lockdep_is_held(l))
>
> We can mimic the structure in get_restripe_target(), but we need to
> make sure lockdep_is_held() is defined for the !LOCKDEP case.
>
> CC: Ilya Dryomov <idryomov@gmail.com>
> CC: Chris Mason <chris.mason@oracle.com>
> CC: Andi Kleen <ak@linux.intel.com>
> CC: Jeff Mahoney <jeffm@suse.de>
> CC: Ingo Molnar <mingo@redhat.com>
> CC: linux-kernel@vger.kernel.org
> Signed-off-by: Bobby Powers <bobbypowers@gmail.com>
> ---
> =A0fs/btrfs/extent-tree.c =A0| =A0 =A05 +++--
> =A0include/linux/lockdep.h | =A0 =A01 +
> =A02 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index a844204..4d13eb1 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -24,6 +24,7 @@
> =A0#include <linux/kthread.h>
> =A0#include <linux/slab.h>
> =A0#include <linux/ratelimit.h>
> +#include <linux/lockdep.h>
> =A0#include "compat.h"
> =A0#include "hash.h"
> =A0#include "ctree.h"
> @@ -3158,8 +3159,8 @@ static u64 get_restripe_target(struct btrfs_fs_=
info *fs_info, u64 flags)
> =A0 =A0 =A0 =A0struct btrfs_balance_control *bctl =3D fs_info->balanc=
e_ctl;
> =A0 =A0 =A0 =A0u64 target =3D 0;
>
> - =A0 =A0 =A0 BUG_ON(!mutex_is_locked(&fs_info->volume_mutex) &&
> - =A0 =A0 =A0 =A0 =A0 =A0 =A0!spin_is_locked(&fs_info->balance_lock))=
;
> + =A0 =A0 =A0 BUG_ON(debug_locks && !lockdep_is_held(&fs_info->volume=
_mutex) &&
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0!lockdep_is_held(&fs_info->balance_lock)=
);
>
> =A0 =A0 =A0 =A0if (!bctl)
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0return 0;
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index d36619e..94c0edb 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -392,6 +392,7 @@ struct lock_class_key { };
>
> =A0#define lockdep_depth(tsk) =A0 =A0 (0)
>
> +#define lockdep_is_held(l) =A0 =A0 (0)
> =A0#define lockdep_assert_held(l) =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 do =
{ } while (0)
>
> =A0#define lockdep_recursing(tsk) =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (0)
> --
> 1.7.10.rc3.3.g19a6c
>
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