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>
This commit is contained in:
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469738e675
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29bde09378
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@ -452,6 +452,23 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
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make_response(blkif, req->id, req->operation, status);
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make_response(blkif, req->id, req->operation, status);
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}
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}
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static void xen_blk_drain_io(struct xen_blkif *blkif)
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{
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atomic_set(&blkif->drain, 1);
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do {
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wait_for_completion_interruptible_timeout(
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&blkif->drain_complete, HZ);
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if (!atomic_read(&blkif->drain))
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break;
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/* The initial value is one, and one refcnt taken at the
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* start of the xen_blkif_schedule thread. */
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if (atomic_read(&blkif->refcnt) <= 2)
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break;
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} while (!kthread_should_stop());
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atomic_set(&blkif->drain, 0);
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}
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/*
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/*
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* Completion callback on the bio's. Called as bh->b_end_io()
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* Completion callback on the bio's. Called as bh->b_end_io()
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*/
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*/
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@ -464,6 +481,11 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
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pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
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pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
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xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
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xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
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pending_req->status = BLKIF_RSP_EOPNOTSUPP;
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pending_req->status = BLKIF_RSP_EOPNOTSUPP;
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} else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
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(error == -EOPNOTSUPP)) {
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pr_debug(DRV_PFX "write barrier op failed, not supported\n");
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xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
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pending_req->status = BLKIF_RSP_EOPNOTSUPP;
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} else if (error) {
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} else if (error) {
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pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
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pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
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" error=%d\n", error);
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" error=%d\n", error);
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@ -481,6 +503,10 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
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pending_req->operation, pending_req->status);
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pending_req->operation, pending_req->status);
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xen_blkif_put(pending_req->blkif);
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xen_blkif_put(pending_req->blkif);
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free_req(pending_req);
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free_req(pending_req);
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if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
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if (atomic_read(&pending_req->blkif->drain))
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complete(&pending_req->blkif->drain_complete);
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}
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}
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}
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}
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}
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@ -574,7 +600,6 @@ do_block_io_op(struct xen_blkif *blkif)
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return more_to_do;
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return more_to_do;
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}
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}
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/*
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/*
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* Transmutation of the 'struct blkif_request' to a proper 'struct bio'
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* Transmutation of the 'struct blkif_request' to a proper 'struct bio'
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* and call the 'submit_bio' to pass it to the underlying storage.
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* and call the 'submit_bio' to pass it to the underlying storage.
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@ -591,6 +616,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
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int i, nbio = 0;
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int i, nbio = 0;
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int operation;
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int operation;
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struct blk_plug plug;
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struct blk_plug plug;
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bool drain = false;
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switch (req->operation) {
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switch (req->operation) {
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case BLKIF_OP_READ:
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case BLKIF_OP_READ:
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@ -601,6 +627,8 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
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blkif->st_wr_req++;
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blkif->st_wr_req++;
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operation = WRITE_ODIRECT;
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operation = WRITE_ODIRECT;
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break;
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break;
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case BLKIF_OP_WRITE_BARRIER:
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drain = true;
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case BLKIF_OP_FLUSH_DISKCACHE:
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case BLKIF_OP_FLUSH_DISKCACHE:
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blkif->st_f_req++;
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blkif->st_f_req++;
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operation = WRITE_FLUSH;
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operation = WRITE_FLUSH;
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@ -609,7 +637,6 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
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blkif->st_ds_req++;
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blkif->st_ds_req++;
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operation = REQ_DISCARD;
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operation = REQ_DISCARD;
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break;
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break;
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case BLKIF_OP_WRITE_BARRIER:
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default:
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default:
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operation = 0; /* make gcc happy */
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operation = 0; /* make gcc happy */
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goto fail_response;
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goto fail_response;
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@ -668,6 +695,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
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}
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}
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}
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}
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/* Wait on all outstanding I/O's and once that has been completed
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* issue the WRITE_FLUSH.
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*/
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if (drain)
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xen_blk_drain_io(pending_req->blkif);
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/*
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/*
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* If we have failed at this point, we need to undo the M2P override,
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* If we have failed at this point, we need to undo the M2P override,
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* set gnttab_set_unmap_op on all of the grant references and perform
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* set gnttab_set_unmap_op on all of the grant references and perform
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@ -181,6 +181,9 @@ struct xen_blkif {
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atomic_t refcnt;
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atomic_t refcnt;
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wait_queue_head_t wq;
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wait_queue_head_t wq;
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/* for barrier (drain) requests */
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struct completion drain_complete;
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atomic_t drain;
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/* One thread per one blkif. */
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/* One thread per one blkif. */
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struct task_struct *xenblkd;
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struct task_struct *xenblkd;
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unsigned int waiting_reqs;
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unsigned int waiting_reqs;
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@ -229,6 +232,8 @@ int xen_blkif_schedule(void *arg);
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int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
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int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
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struct backend_info *be, int state);
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struct backend_info *be, int state);
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int xen_blkbk_barrier(struct xenbus_transaction xbt,
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struct backend_info *be, int state);
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struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be);
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struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be);
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static inline void blkif_get_x86_32_req(struct blkif_request *dst,
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static inline void blkif_get_x86_32_req(struct blkif_request *dst,
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@ -114,6 +114,8 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
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spin_lock_init(&blkif->blk_ring_lock);
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spin_lock_init(&blkif->blk_ring_lock);
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atomic_set(&blkif->refcnt, 1);
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atomic_set(&blkif->refcnt, 1);
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init_waitqueue_head(&blkif->wq);
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init_waitqueue_head(&blkif->wq);
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init_completion(&blkif->drain_complete);
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atomic_set(&blkif->drain, 0);
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blkif->st_print = jiffies;
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blkif->st_print = jiffies;
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init_waitqueue_head(&blkif->waiting_to_free);
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init_waitqueue_head(&blkif->waiting_to_free);
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@ -474,6 +476,19 @@ kfree:
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out:
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out:
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return err;
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return err;
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}
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}
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int xen_blkbk_barrier(struct xenbus_transaction xbt,
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struct backend_info *be, int state)
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{
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struct xenbus_device *dev = be->dev;
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int err;
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err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
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"%d", state);
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if (err)
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xenbus_dev_fatal(dev, err, "writing feature-barrier");
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return err;
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}
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/*
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/*
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* Entry point to this code when a new device is created. Allocate the basic
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* Entry point to this code when a new device is created. Allocate the basic
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@ -708,6 +723,9 @@ again:
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err = xen_blkbk_discard(xbt, be);
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err = xen_blkbk_discard(xbt, be);
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/* If we can't advertise it is OK. */
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err = xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
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err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
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err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
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(unsigned long long)vbd_sz(&be->blkif->vbd));
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(unsigned long long)vbd_sz(&be->blkif->vbd));
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if (err) {
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if (err) {
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