Dave Boutcher wrote:
On Tue, 18 Jul 2006 00:00:33 -0700, Chris Wright <[email protected]> said:
The block device frontend driver allows the kernel to access block
devices exported exported by a virtual machine containing a physical
block device driver.
First, I think this belongs in drivers/block (and the network driver
belongs in drivers/net). If we're going to bring xen to the party,
lets not leave it hiding out in a corner.
+static void connect(struct blkfront_info *);
+static void blkfront_closing(struct xenbus_device *);
+static int blkfront_remove(struct xenbus_device *);
+static int talk_to_backend(struct xenbus_device *, struct blkfront_info *);
+static int setup_blkring(struct xenbus_device *, struct blkfront_info *);
+
+static void kick_pending_request_queues(struct blkfront_info *);
+
+static irqreturn_t blkif_int(int irq, void *dev_id, struct pt_regs *ptregs);
+static void blkif_restart_queue(void *arg);
+static void blkif_recover(struct blkfront_info *);
+static void blkif_completion(struct blk_shadow *);
+static void blkif_free(struct blkfront_info *, int);
I'm pretty sure you can rearrange the code to get rid of the forward
references.
+/**
+ * We are reconnecting to the backend, due to a suspend/resume, or a backend
+ * driver restart. We tear down our blkif structure and recreate it, but
+ * leave the device-layer structures intact so that this is transparent to the
+ * rest of the kernel.
+ */
+static int blkfront_resume(struct xenbus_device *dev)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+ int err;
+
+ DPRINTK("blkfront_resume: %s\n", dev->nodename);
+
+ blkif_free(info, 1);
+
+ err = talk_to_backend(dev, info);
+ if (!err)
+ blkif_recover(info);
+
+ return err;
+}
Should blkfront_resume grab blkif_io_lock?
There should be no concurrent activity until info->connected has been
set to BLKIF_STATE_CONNECTED, which doesn't happen until blkif_recover
has completed successfully. blkif_queue_request and blkif_int both test
the connection state before doing anything. (Not sure if a concurrent
XenBus event can happen though.)
+static inline int GET_ID_FROM_FREELIST(
+ struct blkfront_info *info)
+{
+ unsigned long free = info->shadow_free;
+ BUG_ON(free > BLK_RING_SIZE);
+ info->shadow_free = info->shadow[free].req.id;
+ info->shadow[free].req.id = 0x0fffffee; /* debug */
+ return free;
+}
+
+static inline void ADD_ID_TO_FREELIST(
+ struct blkfront_info *info, unsigned long id)
+{
+ info->shadow[id].req.id = info->shadow_free;
+ info->shadow[id].request = 0;
+ info->shadow_free = id;
+}
A real nit..but why are these routines SHOUTING?
+int blkif_release(struct inode *inode, struct file *filep)
+{
+ struct blkfront_info *info = inode->i_bdev->bd_disk->private_data;
+ info->users--;
+ if (info->users == 0) {
Hrm...this strikes me as racey. Don't you need at least a memory
barrier here to handle SMP?
Hm. Doesn't look good to me.
+static struct xlbd_major_info xvd_major_info = {
+ .major = 201,
+ .type = &xvd_type_info
+};
I've forgotten what the current policy is around new major numbers.
This is wrong. 201 is allocated to Veritas, but 202 has been allocated
for the Xen VBD.
J
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