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authorBob Liu <bob.liu@oracle.com>2015-06-19 07:23:00 +0300
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2015-06-22 17:06:29 +0300
commita9b54bb95176cd27f952cd9647849022c4c998d6 (patch)
tree80cd735b3b9c175ca1dbccba75042b0735337647 /drivers/block
parent86839c56dee28c315a4c19b7bfee450ccd84cd25 (diff)
downloadlinux-a9b54bb95176cd27f952cd9647849022c4c998d6.tar.xz
drivers: xen-blkfront: only talk_to_blkback() when in XenbusStateInitialising
Patch 69b91ede5cab843dcf345c28bd1f4b5a99dacd9b "drivers: xen-blkback: delay pending_req allocation to connect_ring" exposed an problem that Xen blkfront has. There is a race with XenStored and the drivers such that we can see two: vbd vbd-268440320: blkfront:blkback_changed to state 2. vbd vbd-268440320: blkfront:blkback_changed to state 2. vbd vbd-268440320: blkfront:blkback_changed to state 4. state changes to XenbusStateInitWait ('2'). The end result is that blkback_changed() receives two notify and calls twice setup_blkring(). While the backend driver may only get the first setup_blkring() which is wrong and reads out-dated (or reads them as they are being updated with new ring-ref values). The end result is that the ring ends up being incorrectly set. The other drivers in the tree have such checks already in. Reported-and-Tested-by: Robert Butera <robert.butera@oracle.com> Signed-off-by: Bob Liu <bob.liu@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/xen-blkfront.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index d3c1a9523d1f..fc770b7d3beb 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1951,6 +1951,8 @@ static void blkback_changed(struct xenbus_device *dev,
switch (backend_state) {
case XenbusStateInitWait:
+ if (dev->state != XenbusStateInitialising)
+ break;
if (talk_to_blkback(dev, info)) {
kfree(info);
dev_set_drvdata(&dev->dev, NULL);