[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [RFC PATCH 33/33] Add Xen virtual block device driver.
Dave Boutcher wrote: On Tue, 18 Jul 2006 00:00:33 -0700, Chris Wright <chrisw@xxxxxxxxxxxx> 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 forwardreferences.+/** + * 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. This is wrong. 201 is allocated to Veritas, but 202 has been allocated for the Xen VBD.+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. J _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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