On Nov 12, 2013, at 11:41 AM, David Howells <[email protected]> wrote:
> Add a system call to make extended file stats available, including file
> creation time, inode version and data version where available through the
> underlying filesystem.
[snip]
> The defined bits in st_ioc_flags are the usual FS_xxx_FL, plus some extra
> flags
> that might be supplied by the filesystem. Note that Ext4 returns flags
> outside
> of {EXT4,FS}_FL_USER_VISIBLE in response to FS_IOC_GETFLAGS. Should
> {EXT4,FS}_FL_USER_VISIBLE be extended to cover them? Or should the extra
> flags
> be suppressed?
This is a bug in the ext4 code. EXT4_FL_USER_VISIBLE should be extended to
cover
all of the flags that are useful to userspace.
> diff --git a/fs/stat.c b/fs/stat.c
> index d0ea7ef75e26..a5e603753bd3 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> +/**
> + * vfs_fstatx - Get the enhanced basic attributes by file descriptor
> + * @fd: The file descriptor refering to the file of interest
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_xgetattr(). The main difference is
> + * that it uses a file descriptor to determine the file location.
> + *
> + * The caller must have preset stat->query_flags, stat->request_mask and
> + * stat->auxinfo as for vfs_xgetattr().
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_fstatx(unsigned int fd, struct kstat *stat)
> {
> struct fd f = fdget_raw(fd);
> int error = -EBADF;
>
> if (f.file) {
> - error = vfs_getattr(&f.file->f_path, stat);
> + error = vfs_xgetattr(&f.file->f_path, stat);
> fdput(f);
> }
> return error;
> }
> +EXPORT_SYMBOL(vfs_fstatx);
> +
> +/**
> + * vfs_fstat - Get basic attributes by file descriptor
> + * @fd: The file descriptor refering to the file of interest
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_getattr(). The main difference is
Typo above - vfs_fstat() is a wrapper around vfs_fstatx().
> + * that it uses a file descriptor to determine the file location.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_fstat(unsigned int fd, struct kstat *stat)
> +{
> + stat->query_flags = 0;
> + stat->request_mask = STATX_BASIC_STATS;
> + stat->auxinfo = NULL;
> + return vfs_fstatx(fd, stat);
> +}
> EXPORT_SYMBOL(vfs_fstat);
[snip]
> +/*
> + * Flags to be st_mask
> + *
> + * Query request/result mask for statxat() and struct statx::st_mask.
> + *
> + * These bits should be set in the mask argument of statxat() to request
> + * particular items when calling statxat().
> + */
> +#define STATX_MODE 0x00000001U /* Want/got st_mode */
> +#define STATX_NLINK 0x00000002U /* Want/got st_nlink */
> +#define STATX_UID 0x00000004U /* Want/got st_uid */
> +#define STATX_GID 0x00000008U /* Want/got st_gid */
> +#define STATX_RDEV 0x00000010U /* Want/got st_rdev */
> +#define STATX_ATIME 0x00000020U /* Want/got st_atime */
> +#define STATX_MTIME 0x00000040U /* Want/got st_mtime */
> +#define STATX_CTIME 0x00000080U /* Want/got st_ctime */
> +#define STATX_INO 0x00000100U /* Want/got st_ino */
> +#define STATX_SIZE 0x00000200U /* Want/got st_size */
> +#define STATX_BLOCKS 0x00000400U /* Want/got st_blocks */
> +#define STATX_ALLOC_BLKSIZE 0x00000800U /* Want/got st_alloc_blksize */
> +#define STATX_IO_PARAMS 0x00000800U /* Want/got I/O
> parameters */
> +#define STATX_BASIC_STATS 0x00000fffU /* The stuff in the normal stat
> struct */
Does it make sense for code clarity to #define STATX_BASIC_STATS explicitly in
terms
of the symbolic STATX_* fields, instead of just the numeric value?
> +#define STATX_BTIME 0x00001000U /* Want/got st_btime */
> +#define STATX_VERSION 0x00002000U /* Want/got st_version
> */
> +#define STATX_IOC_FLAGS 0x00004000U /* Want/got
> FS_IOC_GETFLAGS */
> +#define STATX_ALL_STATS 0x00007fffU /* All supported stats
> */
This could be #defined in terms of STATX_BASIC_STATS | STATX_{other flags} to
make
it easier to see what is in the basic flags, and what is extra.
Cheers, Andreas
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