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 <matthew.r.wilcox@intel.com>
Acked-by: Dave Chinner <david@fromorbit.com>
Cc: Dheeraj Reddy <dheeraj.reddy@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/brd.c

@@ -200,11 +200,11 @@ static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
 
 	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;
 }
@@ -384,7 +384,7 @@ static int brd_direct_access(struct block_device *bdev, sector_t sector,
 		return -ERANGE;
 	page = brd_insert_page(brd, sector);
 	if (!page)
-		return -ENOMEM;
+		return -ENOSPC;
 	*kaddr = page_address(page);
 	*pfn = page_to_pfn(page);