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| author | Juergen Gross <jgross@suse.com> | 2017-05-18 18:28:47 +0300 |
|---|---|---|
| committer | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2017-06-13 23:04:18 +0300 |
| commit | 46464411307746e6297a034a9983a22c9dfc5a0c (patch) | |
| tree | 10a7411cf52e3cbe830d4a48f44cf1eb93085c31 /drivers/block | |
| parent | 2d4456c73a487abe53863e10641c2f73537edf5c (diff) | |
| download | linux-46464411307746e6297a034a9983a22c9dfc5a0c.tar.xz | |
xen/blkback: fix disconnect while I/Os in flight
Today disconnecting xen-blkback is broken in case there are still
I/Os in flight: xen_blkif_disconnect() will bail out early without
releasing all resources in the hope it will be called again when
the last request has terminated. This, however, won't happen as
xen_blkif_free() won't be called on termination of the last running
request: xen_blkif_put() won't decrement the blkif refcnt to 0 as
xen_blkif_disconnect() didn't finish before thus some xen_blkif_put()
calls in xen_blkif_disconnect() didn't happen.
To solve this deadlock xen_blkif_disconnect() and
xen_blkif_alloc_rings() shouldn't use xen_blkif_put() and
xen_blkif_get() but use some other way to do their accounting of
resources.
This at once fixes another error in xen_blkif_disconnect(): when it
returned early with -EBUSY for another ring than 0 it would call
xen_blkif_put() again for already handled rings on a subsequent call.
This will lead to inconsistencies in the refcnt handling.
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Steven Haigh <netwiz@crc.id.au>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block')
| -rw-r--r-- | drivers/block/xen-blkback/common.h | 1 | ||||
| -rw-r--r-- | drivers/block/xen-blkback/xenbus.c | 7 |
2 files changed, 6 insertions, 2 deletions
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index dea61f6ab8cb..638597b17a38 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -281,6 +281,7 @@ struct xen_blkif_ring { wait_queue_head_t wq; atomic_t inflight; + bool active; /* One thread per blkif ring. */ struct task_struct *xenblkd; unsigned int waiting_reqs; diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 1f3dfaa54d87..998915174bb8 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -159,7 +159,7 @@ static int xen_blkif_alloc_rings(struct xen_blkif *blkif) init_waitqueue_head(&ring->shutdown_wq); ring->blkif = blkif; ring->st_print = jiffies; - xen_blkif_get(blkif); + ring->active = true; } return 0; @@ -249,6 +249,9 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif) struct xen_blkif_ring *ring = &blkif->rings[r]; unsigned int i = 0; + if (!ring->active) + continue; + if (ring->xenblkd) { kthread_stop(ring->xenblkd); wake_up(&ring->shutdown_wq); @@ -296,7 +299,7 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif) BUG_ON(ring->free_pages_num != 0); BUG_ON(ring->persistent_gnt_c != 0); WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages)); - xen_blkif_put(blkif); + ring->active = false; } blkif->nr_ring_pages = 0; /* |