Re: [PATCH 3/3] Add a pair of system calls to make extended filestats available [ver #2]

[Nicholas Miell]

On Wed, 2010-06-30 at 02:17 +0100, David Howells wrote:
> Add a pair of system calls to make extended file stats available, including
> file creation time, inode version and data version where available through the
> underlying filesystem:
> 
> 	struct xstat_dev {
> 		unsigned int	major;
> 		unsigned int	minor;
> 	};
> 
> 	struct xstat_time {
> 		unsigned long long	tv_sec;
> 		unsigned long long	tv_nsec;
> 	};
> 
> 	struct xstat {
> 		unsigned int		struct_version;
> 	#define XSTAT_STRUCT_VERSION	0
> 		unsigned int		st_mode;
> 		unsigned int		st_nlink;
> 		unsigned int		st_uid;
> 		unsigned int		st_gid;
> 		unsigned int		st_blksize;
> 		struct xstat_dev	st_rdev;
> 		struct xstat_dev	st_dev;
> 		unsigned long long	st_ino;
> 		unsigned long long	st_size;
> 		struct xstat_time	st_atime;
> 		struct xstat_time	st_mtime;
> 		struct xstat_time	st_ctime;
> 		struct xstat_time	st_btime;
> 		unsigned long long	st_blocks;
> 		unsigned long long	st_gen;
> 		unsigned long long	st_data_version;
> 		unsigned long long	query_flags;
> 	#define XSTAT_QUERY_SIZE		0x00000001ULL
> 	#define XSTAT_QUERY_NLINK		0x00000002ULL
> 	#define XSTAT_QUERY_AMC_TIMES		0x00000004ULL
> 	#define XSTAT_QUERY_CREATION_TIME	0x00000008ULL
> 	#define XSTAT_QUERY_BLOCKS		0x00000010ULL
> 	#define XSTAT_QUERY_INODE_GENERATION	0x00000020ULL
> 	#define XSTAT_QUERY_DATA_VERSION	0x00000040ULL
> 		unsigned long long	extra_results[0];
> 	};
> 

unsigned long long inside a struct has 4 byte alignment on x86, while
AMD64 has 8 byte alignment. This struct layout isn't affected by the
difference, but that's something to keep in mind.
-- 
Nicholas Miell <nmiell@xxxxxxxxxxx>

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