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authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2011-10-10 00:42:22 -0400
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2011-10-13 09:48:36 -0400
commit29bde093787f3bdf7b9b4270ada6be7c8076e36b (patch)
tree4fff697e0acb2471b1bd575cbd006fa4efc3937d /drivers/block/xen-blkback/blkback.c
parent469738e675524b6aa029ecd46bdda3f878b12eff (diff)
xen/blkback: Support 'feature-barrier' aka old-style BARRIER requests.
We emulate the barrier requests by draining the outstanding bio's and then sending the WRITE_FLUSH command. To drain the I/Os we use the refcnt that is used during disconnect to wait for all the I/Os before disconnecting from the frontend. We latch on its value and if it reaches either the threshold for disconnect or when there are no more outstanding I/Os, then we have drained all I/Os. Suggested-by: Christopher Hellwig <hch@infradead.org> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block/xen-blkback/blkback.c')
-rw-r--r--drivers/block/xen-blkback/blkback.c37
1 files changed, 35 insertions, 2 deletions
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index e0dab614049c..184b1335c8e9 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -452,6 +452,23 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
make_response(blkif, req->id, req->operation, status);
}
+static void xen_blk_drain_io(struct xen_blkif *blkif)
+{
+ atomic_set(&blkif->drain, 1);
+ do {
+ wait_for_completion_interruptible_timeout(
+ &blkif->drain_complete, HZ);
+
+ if (!atomic_read(&blkif->drain))
+ break;
+ /* The initial value is one, and one refcnt taken at the
+ * start of the xen_blkif_schedule thread. */
+ if (atomic_read(&blkif->refcnt) <= 2)
+ break;
+ } while (!kthread_should_stop());
+ atomic_set(&blkif->drain, 0);
+}
+
/*
* Completion callback on the bio's. Called as bh->b_end_io()
*/
@@ -464,6 +481,11 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
pending_req->status = BLKIF_RSP_EOPNOTSUPP;
+ } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
+ (error == -EOPNOTSUPP)) {
+ pr_debug(DRV_PFX "write barrier op failed, not supported\n");
+ xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
+ pending_req->status = BLKIF_RSP_EOPNOTSUPP;
} else if (error) {
pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
" error=%d\n", error);
@@ -481,6 +503,10 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
pending_req->operation, pending_req->status);
xen_blkif_put(pending_req->blkif);
free_req(pending_req);
+ if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
+ if (atomic_read(&pending_req->blkif->drain))
+ complete(&pending_req->blkif->drain_complete);
+ }
}
}
@@ -574,7 +600,6 @@ do_block_io_op(struct xen_blkif *blkif)
return more_to_do;
}
-
/*
* Transmutation of the 'struct blkif_request' to a proper 'struct bio'
* and call the 'submit_bio' to pass it to the underlying storage.
@@ -591,6 +616,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
int i, nbio = 0;
int operation;
struct blk_plug plug;
+ bool drain = false;
switch (req->operation) {
case BLKIF_OP_READ:
@@ -601,6 +627,8 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
blkif->st_wr_req++;
operation = WRITE_ODIRECT;
break;
+ case BLKIF_OP_WRITE_BARRIER:
+ drain = true;
case BLKIF_OP_FLUSH_DISKCACHE:
blkif->st_f_req++;
operation = WRITE_FLUSH;
@@ -609,7 +637,6 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
blkif->st_ds_req++;
operation = REQ_DISCARD;
break;
- case BLKIF_OP_WRITE_BARRIER:
default:
operation = 0; /* make gcc happy */
goto fail_response;
@@ -668,6 +695,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
}
}
+ /* Wait on all outstanding I/O's and once that has been completed
+ * issue the WRITE_FLUSH.
+ */
+ if (drain)
+ xen_blk_drain_io(pending_req->blkif);
+
/*
* If we have failed at this point, we need to undo the M2P override,
* set gnttab_set_unmap_op on all of the grant references and perform