On Fri, May 25, 2018 at 2:08 AM, David Howells <dhowells@xxxxxxxxxx> wrote:
> +
> +static int fsinfo_generic_timestamp_info(struct dentry *dentry,
> + struct fsinfo_timestamp_info *ts)
> +{
> + struct super_block *sb = dentry->d_sb;
> +
> + /* If unset, assume 1s granularity */
> + u16 mantissa = 1;
> + s8 exponent = 0;
> +
> + ts->minimum_timestamp = S64_MIN;
> + ts->maximum_timestamp = S64_MAX;
> + if (sb->s_time_gran < 1000000000) {
> + if (sb->s_time_gran < 1000)
> + exponent = -9;
> + else if (sb->s_time_gran < 1000000)
> + exponent = -6;
> + else
> + exponent = -3;
> + }
ntfs has sb->s_time_gran=100, and vfat should really have
sb->s_time_gran=2000000000 but that doesn't seem to be set right
at the moment.
> +/*
> + * Optional fsinfo() parameter structure.
> + *
> + * If this is not given, it is assumed that fsinfo_attr_statfs instance 0 is
> + * desired.
> + */
> +struct fsinfo_params {
> + enum fsinfo_attribute request; /* What is being asking for */
> + __u32 Nth; /* Instance of it (some may have multiple) */
> + __u32 at_flags; /* AT_SYMLINK_NOFOLLOW and similar flags */
> + __u32 __spare[6]; /* Spare params; all must be 0 */
> +};
I fear the 'enum' in the uapi structure may have a different size depending
on the architecture. Maybe turn that into a __u32 as well?
> +struct fsinfo_capabilities {
> + __u64 supported_stx_attributes; /* What statx::stx_attributes are supported */
> + __u32 supported_stx_mask; /* What statx::stx_mask bits are supported */
> + __u32 supported_ioc_flags; /* What FS_IOC_* flags are supported */
> + __u8 capabilities[(fsinfo_cap__nr + 7) / 8];
> +};
This looks a bit odd: with the 44 capabilities, you end up having a
six-byte array
followed by two bytes of implicit padding. If the number of
capabilities grows beyond
64, you have a nine byte array with more padding to the next alignof(__u64). Is
that intentional?
How about making it a fixed size with either 64 or 128 capability bits?
> +/*
> + * Information struct for fsinfo(fsinfo_attr_timestamp_info).
> + */
> +struct fsinfo_timestamp_info {
> + __s64 minimum_timestamp; /* Minimum timestamp value in seconds */
> + __s64 maximum_timestamp; /* Maximum timestamp value in seconds */
> + __u16 atime_gran_mantissa; /* Granularity(secs) = mant * 10^exp */
> + __u16 btime_gran_mantissa;
> + __u16 ctime_gran_mantissa;
> + __u16 mtime_gran_mantissa;
> + __s8 atime_gran_exponent;
> + __s8 btime_gran_exponent;
> + __s8 ctime_gran_exponent;
> + __s8 mtime_gran_exponent;
> +};
This structure has a slightly inconsistent amount of padding at the end:
on x86-32 it has no padding, everywhere else it has 32 bits of padding
to make it 64-bit aligned. Maybe add a __u32 reserved field?
> +
> +#define __NR_fsinfo 326
Hardcoding the syscall number in the example makes it architecture specific.
Could you include <asm/unistd.h> to get the real number?
Arnd
