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drbd: cleanup bogus assert message

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This fixes ASSERT( mdev->state.disk == D_FAILED ) in drivers/block/drbd/drbd_main.c

When we detach from local disk, we let the local refcount hit zero twice.

First, we transition to D_FAILED, so we won't give out new references
to incoming requests; we still may give out *internal* references, though.
Once the refcount hits zero [1] while in D_FAILED, we queue a transition
to D_DISKLESS to our worker.  We need to queue it, because we may be in
atomic context when putting the reference.
Once the transition to D_DISKLESS actually happened [2] from worker context,
we don't give out new internal references either.

Between hitting zero the first time [1] and actually transition to
D_DISKLESS [2], there may be a few very short lived internal get/put,
so we may hit zero more than once while being in D_FAILED, or even see a
race where a an internal get_ldev() happened while D_FAILED, but the
corresponding put_ldev() happens just after the transition to D_DISKLESS.

That's why we have the additional test_and_set_bit(GO_DISKLESS,);
and that's why the assert was placed wrong.
Since there was exactly one code path left to drbd_go_diskless(),
and that checks already for D_FAILED, drop that assert,
and fold in the drbd_queue_work().

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Lars Ellenberg 2013-03-19 18:16:42 +01:00 committed by Jens Axboe
parent a937536b86
commit 9114d79569
2 changed files with 4 additions and 10 deletions
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7
drivers/block/drbd/drbd_int.h
View File

@ -1148,7 +1148,6 @@ extern int drbd_bitmap_io_from_worker(struct drbd_conf *mdev,
char *why, enum bm_flag flags);
extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
extern void drbd_go_diskless(struct drbd_conf *mdev);
extern void drbd_ldev_destroy(struct drbd_conf *mdev);
/* Meta data layout
@ -2053,9 +2052,11 @@ static inline void put_ldev(struct drbd_conf *mdev)
if (mdev->state.disk == D_DISKLESS)
/* even internal references gone, safe to destroy */
drbd_ldev_destroy(mdev);
if (mdev->state.disk == D_FAILED)
if (mdev->state.disk == D_FAILED) {
/* all application IO references gone. */
drbd_go_diskless(mdev);
if (!test_and_set_bit(GO_DISKLESS, &mdev->flags))
drbd_queue_work(&mdev->tconn->sender_work, &mdev->go_diskless);
}
wake_up(&mdev->misc_wait);
}
}

7
drivers/block/drbd/drbd_main.c
View File

@ -3252,13 +3252,6 @@ static int w_go_diskless(struct drbd_work *w, int unused)
return 0;
}
void drbd_go_diskless(struct drbd_conf *mdev)
{
D_ASSERT(mdev->state.disk == D_FAILED);
if (!test_and_set_bit(GO_DISKLESS, &mdev->flags))
drbd_queue_work(&mdev->tconn->sender_work, &mdev->go_diskless);
}
/**
* drbd_queue_bitmap_io() - Queues an IO operation on the whole bitmap
* @mdev: DRBD device.