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From:   =?UTF-8?q?Christoph=20B=C3=B6hmwalder?= 
        <christoph.boehmwalder@linbit.com>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     drbd-dev@lists.linbit.com, linux-kernel@vger.kernel.org,
        Lars Ellenberg <lars.ellenberg@linbit.com>,
        Philipp Reisner <philipp.reisner@linbit.com>,
        linux-block@vger.kernel.org,
        =?UTF-8?q?Christoph=20B=C3=B6hmwalder?= 
        <christoph.boehmwalder@linbit.com>
Subject: [PATCH 7/8] drbd: interval tree: make removing an "empty" interval a no-op
Date:   Fri, 13 Jan 2023 13:35:37 +0100
Message-Id: <20230113123538.144276-8-christoph.boehmwalder@linbit.com>
In-Reply-To: <20230113123538.144276-1-christoph.boehmwalder@linbit.com>
References: <20230113123538.144276-1-christoph.boehmwalder@linbit.com>
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From: Lars Ellenberg <lars.ellenberg@linbit.com>

Trying to remove an "empty" (just initialized, or "cleared") interval
from the tree, this results in an endless loop.

As we typically protect the tree with a spinlock_irq,
the result is a hung system.

Be nice to error cleanup code paths, ignore removal of empty intervals.

Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_interval.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/drbd/drbd_interval.c b/drivers/block/drbd/drbd_interval.c
index 5024ffd6143d..b6aaf0d4d85b 100644
--- a/drivers/block/drbd/drbd_interval.c
+++ b/drivers/block/drbd/drbd_interval.c
@@ -95,6 +95,10 @@ drbd_contains_interval(struct rb_root *root, sector_t sector,
 void
 drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
 {
+	/* avoid endless loop */
+	if (drbd_interval_empty(this))
+		return;
+
 	rb_erase_augmented(&this->rb, root, &augment_callbacks);
 }
 
-- 
2.38.1