-----Original Message-----
From: Christoph Hellwig [mailto:hch@infradead.org]
Sent: Tuesday, August 4, 2015 7:28 AM
To: Shaohua Li
Cc: linux-raid@vger.kernel.org; Kernel Team; Song Liu; hch@infradead.org;
dan.j.williams@intel.com; neilb@suse.de
Subject: Re: [PATCH 1/9] MD: add a new disk role to present cache device

quoted

 		case 0xfffe: /* faulty */
 			set_bit(Faulty, &rdev->flags);
 			break;
+		case 0xfffd: /* cache device */

Any chance to get constants for these magic numbers as an additional prep
patch?

I will add patch for special roles (spare, faulty, cache, etc.). 

Also I don't really think that adding the role without the actual implementation
is that useful.

Currently, we are planning to use 0xfffd for both "cache device" and 
"journal device" (fix write hole only). Would you prefer to separate these
two scenarios with two different roles (0xfffd and 0xfffc)?

Thanks,
Song