Re: [PATCH] lightnvm: work around 32-bit built error

From: Jens Axboe
Date: Tue Nov 03 2015 - 10:26:43 EST

On 11/03/2015 06:53 AM, Arnd Bergmann wrote:
The newly added lightnvm incorrectly uses a sector_t variable to
represent a data structure with fixed length bit fields, which breaks
when sector_t is configured to be 32-bit:

In file included from ../drivers/lightnvm/core.c:29:0:
/include/linux/lightnvm.h:143:4: error: width of 'resved' exceeds its type
sector_t resved : 36;
include/linux/lightnvm.h: In function 'ppa_set_empty':
/include/linux/lightnvm.h:120:20: warning: large integer implicitly truncated to unsigned type [-Woverflow]
#define ADDR_EMPTY (~0ULL)

Thanks Arnd, Matias sent another variant yesterday that changes this to u64 as well.

This patch resolves the build error, but does not address the fact that
bit fields are not reliable in data structures that are interpreted
by firmware on another architecture. If the layout is meant to be
stable, the bit fields should be replaced with explicit calculations.

Matias? Are these every stored and read back, potentially on a different machine?

Jens Axboe

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