On Mon, 2019-12-09 at 11:08 +0000, Russell King wrote:
> Despite ADFS timestamps having centi-second granularity, and Linux
> gaining fine-grained timestamp support in v2.5.48, fs/adfs was never
> updated.
>
> Update fs/adfs to centi-second support, and ensure that the inode
> ctime
> always reflects what is written in underlying media.
>
> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
> ---
> fs/adfs/inode.c | 40 ++++++++++++++++++++--------------------
> fs/adfs/super.c | 2 ++
> 2 files changed, 22 insertions(+), 20 deletions(-)
>
> diff --git a/fs/adfs/inode.c b/fs/adfs/inode.c
> index 124de75413a5..18a1d478669b 100644
> --- a/fs/adfs/inode.c
> +++ b/fs/adfs/inode.c
> @@ -158,6 +158,8 @@ adfs_mode2atts(struct super_block *sb, struct
> inode *inode)
> return attr;
> }
>
> +static const s64 nsec_unix_epoch_diff_risc_os_epoch =
> 2208988800000000000LL;
> +
> /*
> * Convert an ADFS time to Unix time. ADFS has a 40-bit centi-
> second time
> * referenced to 1 Jan 1900 (til 2248) so we need to discard
> 2208988800 seconds
> @@ -170,8 +172,6 @@ adfs_adfs2unix_time(struct timespec64 *tv, struct
> inode *inode)
> /* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
> * 01 Jan 1900 00:00:00 (RISC OS epoch)
> */
> - static const s64 nsec_unix_epoch_diff_risc_os_epoch =
> - 220898880000000
> 0000LL;
> s64 nsec;
>
> if (!adfs_inode_is_stamped(inode))
> @@ -204,24 +204,23 @@ adfs_adfs2unix_time(struct timespec64 *tv,
> struct inode *inode)
> return;
> }
>
> -/*
> - * Convert an Unix time to ADFS time. We only do this if the entry
> has a
> - * time/date stamp already.
> - */
> -static void
> -adfs_unix2adfs_time(struct inode *inode, unsigned int secs)
> +/* Convert an Unix time to ADFS time for an entry that is already
> stamped. */
> +static void adfs_unix2adfs_time(struct inode *inode,
> + const struct timespec64 *ts)
> {
> - unsigned int high, low;
> + s64 cs, nsec = timespec64_to_ns(ts);
>
> - if (adfs_inode_is_stamped(inode)) {
> - /* convert 32-bit seconds to 40-bit centi-seconds */
> - low = (secs & 255) * 100;
> - high = (secs / 256) * 100 + (low >> 8) + 0x336e996a;
> + /* convert from Unix to RISC OS epoch */
> + nsec += nsec_unix_epoch_diff_risc_os_epoch;
>
> - ADFS_I(inode)->loadaddr = (high >> 24) |
> - (ADFS_I(inode)->loadaddr & ~0xff);
> - ADFS_I(inode)->execaddr = (low & 255) | (high << 8);
> - }
> + /* convert from nanoseconds to centiseconds */
> + cs = div_s64(nsec, 10000000);
> +
> + cs = clamp_t(s64, cs, 0, 0xffffffffff);
> +
> + ADFS_I(inode)->loadaddr &= ~0xff;
> + ADFS_I(inode)->loadaddr |= (cs >> 32) & 0xff;
> + ADFS_I(inode)->execaddr = cs;
> }
>
> /*
> @@ -315,10 +314,11 @@ adfs_notify_change(struct dentry *dentry,
> struct iattr *attr)
> if (ia_valid & ATTR_SIZE)
> truncate_setsize(inode, attr->ia_size);
>
> - if (ia_valid & ATTR_MTIME) {
> - inode->i_mtime = attr->ia_mtime;
> - adfs_unix2adfs_time(inode, attr->ia_mtime.tv_sec);
> + if (ia_valid & ATTR_MTIME && adfs_inode_is_stamped(inode)) {
> + adfs_unix2adfs_time(inode, &attr->ia_mtime);
> + adfs_adfs2unix_time(&inode->i_mtime, inode);
> }
> +
> /*
> * FIXME: should we make these == to i_mtime since we don't
> * have the ability to represent them in our filesystem?
> diff --git a/fs/adfs/super.c b/fs/adfs/super.c
> index 65b04ebb51c3..e0eea9adb4e6 100644
> --- a/fs/adfs/super.c
> +++ b/fs/adfs/super.c
> @@ -391,7 +391,9 @@ static int adfs_fill_super(struct super_block
> *sb, void *data, int silent)
> asb = kzalloc(sizeof(*asb), GFP_KERNEL);
> if (!asb)
> return -ENOMEM;
> +
> sb->s_fs_info = asb;
> + sb->s_time_gran = 10000000;
I believe it's not easy to follow what this granularity means. Maybe,
it makes sense to introduce some constant and to add some comment?
Thanks,
Viacheslav Dubeyko.
>
> /* set default options */
> asb->s_uid = GLOBAL_ROOT_UID;
