rbd: add 'thick' sysfs rbd device attribute

This patch adds the description of sysfs thick entry.

---
 Documentation/ABI/testing/sysfs-bus-rbd | 6 ++++++
 1 file changed, 6 insertions(+)

index f208ac58d613..3023f39328b1 100644
@@ -119,3 +119,9 @@ parent
 
 	Information identifying the chain of parent images in a layered rbd
 	image.  Entries are separated by empty lines.
+
+thick
+
+	Specifying thick-provision image by writing "1" to this file.
+	And, releasing the flag of thick-provision image by writing
+	"0" to this file.

2.15.1

The normal storage term would be fully provisioned, not 'thick'

The rbd command, which is user mode program, uses "thick-provision". If the kernel rbd driver uses "fully provisioned", then the rbd command should use "fully provisioned" too.

What do you think, Jason?

Regards,

Hitoshi Kamei