From b6a370ba0786b5eb09c479bffeffe7baba484ab0 Mon Sep 17 00:00:00 2001 From: Philipp Reisner Date: Sun, 19 Feb 2012 01:27:53 +0100 Subject: [PATCH] drbd: Fix a potential write ordering issue on SyncTarget nodes If a SyncTarget node gets a P_RS_DATA_REPLY before a P_DATA packet for the same sector, it simply submits these two IO requests. This is be possible because on the SyncSource node, the data of the P_RS_DATA_REPLY packet was read from disk. Immediately after that a write request from upper layers came in. The disk scheduler or even the "hardware" queues on the disk drive might reorder these writes. Signed-off-by: Philipp Reisner Signed-off-by: Lars Ellenberg --- drivers/block/drbd/drbd_receiver.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c index 6b0505a3c4fc..d601501c336a 100644 --- a/drivers/block/drbd/drbd_receiver.c +++ b/drivers/block/drbd/drbd_receiver.c @@ -1585,6 +1585,24 @@ static int e_send_discard_ack(struct drbd_conf *mdev, struct drbd_work *w, int u return ok; } +static bool overlapping_resync_write(struct drbd_conf *mdev, struct drbd_epoch_entry *data_e) +{ + + struct drbd_epoch_entry *rs_e; + bool rv = 0; + + spin_lock_irq(&mdev->req_lock); + list_for_each_entry(rs_e, &mdev->sync_ee, w.list) { + if (overlaps(data_e->sector, data_e->size, rs_e->sector, rs_e->size)) { + rv = 1; + break; + } + } + spin_unlock_irq(&mdev->req_lock); + + return rv; +} + /* Called from receive_Data. * Synchronize packets on sock with packets on msock. * @@ -1828,6 +1846,9 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned list_add(&e->w.list, &mdev->active_ee); spin_unlock_irq(&mdev->req_lock); + if (mdev->state.conn == C_SYNC_TARGET) + wait_event(mdev->ee_wait, !overlapping_resync_write(mdev, e)); + switch (mdev->net_conf->wire_protocol) { case DRBD_PROT_C: inc_unacked(mdev); -- 2.30.2