brd: return -ENOSPC rather than -ENOMEM on page allocation failure

brd is effectively a thinly provisioned device. Thinly provisioned
devices return -ENOSPC when they can't write a new block. -ENOMEM is an
implementation detail that callers shouldn't know.

Signed-off-by: Matthew Wilcox <[e-mail]>
Acked-by: Dave Chinner <[e-mail]>
Cc: Dheeraj Reddy <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/block/brd.c

···
 
 	copy = min_t(size_t, n, PAGE_SIZE - offset);
 	if (!brd_insert_page(brd, sector))
-		return -ENOMEM;
+		return -ENOSPC;
 	if (copy < n) {
 		sector += copy >> SECTOR_SHIFT;
 		if (!brd_insert_page(brd, sector))
-			return -ENOMEM;
+			return -ENOSPC;
 	}
 	return 0;
 }
···
 		return -ERANGE;
 	page = brd_insert_page(brd, sector);
 	if (!page)
-		return -ENOMEM;
+		return -ENOSPC;
 	*kaddr = page_address(page);
 	*pfn = page_to_pfn(page);