Re: [RFC PATCH 33/33] Add Xen virtual block device driver.

From: Arjan van de Ven
Date: Tue Jul 18 2006 - 06:33:36 EST

On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
> plain text document attachment (blkfront)
> The block device frontend driver allows the kernel to access block
> devices exported exported by a virtual machine containing a physical
> block device driver.


as first general comment, I think that some of the memory allocation
GFP_ flags are possibly incorrect; I would expect several places to use
GFP_NOIO rather than GFP_KERNEL, to avoid recursion/deadlocks

> +static void blkif_recover(struct blkfront_info *info)
> +{
> + int i;
> + struct blkif_request *req;
> + struct blk_shadow *copy;
> + int j;
> +
> + /* Stage 1: Make a safe copy of the shadow state. */
> + copy = kmalloc(sizeof(info->shadow), GFP_KERNEL | __GFP_NOFAIL);

like here..

> + memcpy(copy, info->shadow, sizeof(info->shadow));

and __GFP_NOFAIL is usually horrid; is this because error recovery was
an afterthought, or because it's physically impossible? In addition
__GFP_NOFAIL in a block device driver is... an interesting way to add
OOM deadlocks... have the VM guys looked into this yet?

> +#if 1
> +#define IPRINTK(fmt, args...) \
> + printk(KERN_INFO "xen_blk: " fmt, ##args)
> +#else
> +#define IPRINTK(fmt, args...) ((void)0)
> +#endif

hmm isn't this a duplication of the pr_debug() and dev_dbg()
infrastructure? Please don't reinvent new ones..

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