Re: [PATCH 08/11] xfs: widen ondisk inode timestamps to deal with y2038+

[Christoph Hellwig <hch@infradead.org>]

> -	tv.tv_sec = (int64_t)t >> 32;
> -	tv.tv_nsec = (int32_t)(t & 0xffffffff);
> +	if (xfs_dinode_has_bigtime(dip)) {
> +		s = xfs_bigtime_to_unix(div_u64_rem(t, NSEC_PER_SEC, &n));
> +	} else {
> +		s = (int64_t)t >> 32;
> +		n = (int32_t)(t & 0xffffffff);

Move this branche into a xfs_legacytime_to_unix helper just to be
symmetric?

This also made me think of the encoding:  another sensible option
would be to always read the time stamps as two 32-bit values using the
struct type, and just add them up for the bigtime case.

> +	if (xfs_inode_has_bigtime(ip))
> +		t = xfs_inode_encode_bigtime(tv);
> +	else
> +		t = ((int64_t)tv.tv_sec << 32) | (tv.tv_nsec & 0xffffffff);
> +

Same here.

> @@ -305,9 +320,9 @@ xfs_inode_to_disk(
>  	to->di_projid_hi = cpu_to_be16(from->di_projid >> 16);
>  
>  	memset(to->di_pad, 0, sizeof(to->di_pad));
> -	to->di_atime = xfs_inode_to_disk_ts(inode->i_atime);
> -	to->di_mtime = xfs_inode_to_disk_ts(inode->i_mtime);
> -	to->di_ctime = xfs_inode_to_disk_ts(inode->i_ctime);
> +	to->di_atime = xfs_inode_to_disk_ts(ip, inode->i_atime);
> +	to->di_mtime = xfs_inode_to_disk_ts(ip, inode->i_mtime);
> +	to->di_ctime = xfs_inode_to_disk_ts(ip, inode->i_ctime);
>  	to->di_nlink = cpu_to_be32(inode->i_nlink);
>  	to->di_gen = cpu_to_be32(inode->i_generation);
>  	to->di_mode = cpu_to_be16(inode->i_mode);
> @@ -326,7 +341,7 @@ xfs_inode_to_disk(
>  	if (xfs_sb_version_has_v3inode(&ip->i_mount->m_sb)) {
>  		to->di_version = 3;
>  		to->di_changecount = cpu_to_be64(inode_peek_iversion(inode));
> -		to->di_crtime = xfs_inode_to_disk_ts(from->di_crtime);
> +		to->di_crtime = xfs_inode_to_disk_ts(ip, from->di_crtime);
>  		to->di_flags2 = cpu_to_be64(from->di_flags2);
>  		to->di_cowextsize = cpu_to_be32(from->di_cowextsize);
>  		to->di_ino = cpu_to_be64(ip->i_ino);
> @@ -546,6 +561,11 @@ xfs_dinode_verify(
>  	if (fa)
>  		return fa;
>  
> +	/* bigtime iflag can only happen on bigtime filesystems */
> +	if (xfs_dinode_has_bigtime(dip) &&
> +	    !xfs_sb_version_hasbigtime(&mp->m_sb))
> +		return __this_address;
> +
>  	return NULL;
>  }
>  
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.h b/fs/xfs/libxfs/xfs_inode_buf.h
> index 3060ecd24a2e..e05bfe52fd8f 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.h
> +++ b/fs/xfs/libxfs/xfs_inode_buf.h
> @@ -32,6 +32,11 @@ struct xfs_icdinode {
>  	struct timespec64 di_crtime;	/* time created */
>  };
>  
> +static inline bool xfs_icdinode_has_bigtime(const struct xfs_icdinode *icd)
> +{
> +	return icd->di_flags2 & XFS_DIFLAG2_BIGTIME;
> +}
> +
>  /*
>   * Inode location information.  Stored in the inode and passed to
>   * xfs_imap_to_bp() to get a buffer and dinode for a given inode.
> @@ -58,6 +63,14 @@ xfs_failaddr_t xfs_inode_validate_cowextsize(struct xfs_mount *mp,
>  		uint32_t cowextsize, uint16_t mode, uint16_t flags,
>  		uint64_t flags2);
>  
> -struct timespec64 xfs_inode_from_disk_ts(const xfs_timestamp_t ts);
> +static inline uint64_t xfs_inode_encode_bigtime(struct timespec64 tv)
> +{
> +	uint64_t	t = xfs_unix_to_bigtime(tv.tv_sec) * NSEC_PER_SEC;
> +
> +	return t + tv.tv_nsec;

Why not:

	return xfs_unix_to_bigtime(tv.tv_sec) * NSEC_PER_SEC + tv.tv_nsec;

?

> +static inline bool xfs_inode_want_bigtime_upgrade(struct xfs_inode *ip)
> +{
> +	return xfs_sb_version_hasbigtime(&ip->i_mount->m_sb) &&
> +	       !xfs_inode_has_bigtime(ip);
> +}
> +
>  /*
>   * This is called to mark the fields indicated in fieldmask as needing to be
>   * logged when the transaction is committed.  The inode must already be
> @@ -131,6 +137,16 @@ xfs_trans_log_inode(
>  			iversion_flags = XFS_ILOG_CORE;
>  	}
>  
> +	/*
> +	 * If we're updating the inode core or the timestamps and it's possible
> +	 * to upgrade this inode to bigtime format, do so now.
> +	 */
> +	if ((flags & (XFS_ILOG_CORE | XFS_ILOG_TIMESTAMP)) &&
> +	    xfs_inode_want_bigtime_upgrade(ip)) {
> +		ip->i_d.di_flags2 |= XFS_DIFLAG2_BIGTIME;
> +		flags |= XFS_ILOG_CORE;
> +	}

I find the way to directly set XFS_DIFLAG2_BIGTIME but using a helper
to check it here rather confusing.

Why not:

	if (xfs_sb_version_hasbigtime(&ip->i_mount->m_sb) &&
	    (flags & (XFS_ILOG_CORE | XFS_ILOG_TIMESTAMP)) &&
	    !(ip->i_d.di_flags2 & XFS_DIFLAG2_BIGTIME)) {
		ip->i_d.di_flags2 |= XFS_DIFLAG2_BIGTIME;
		flags |= XFS_ILOG_CORE;
	}

?