Re: [PATCH v5 7/7] xfs: Support setting FMODE_CAN_ATOMIC_WRITE

On Fri, Aug 23, 2024 at 11:41:07AM +0100, John Garry wrote:

On 22/08/2024 21:44, Darrick J. Wong wrote:

quoted

quoted

Do you mean that add a new member to xfs_inode to record this? If yes, it
sounds ok, but we need to maintain consistency (of that member) whenever
anything which can affect it changes, which is always a bit painful.

I actually meant something more like:

static bool
xfs_file_open_can_atomicwrite(
	struct file		*file,
	struct inode		*inode)
{
	struct xfs_inode	*ip = XFS_I(inode);
	struct xfs_mount	*mp = ip->i_mount;
	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);

	if (!(file->f_flags & O_DIRECT))
		return false;
	if (!xfs_inode_has_atomicwrites(ip))
		return false;
	if (mp->m_dalign && (mp->m_dalign % ip->i_extsize))
		return false;
	if (mp->m_swidth && (mp->m_swidth % ip->i_extsize))
		return false;
	if (mp->m_sb.sb_blocksize < target->bt_bdev_awu_min)
		return false;
	if (xfs_inode_alloc_unitsize(ip) > target->bt_bdev_awu_max)
		return false;
	return true;
}

ok, but we should probably factor out some duplicated code with helpers,
like:

bool xfs_validate_atomicwrites_extsize(struct xfs_mount *mp, uint32_t
extsize)

xfs_agblock_t extsize, but other than that this looks right to me.

{
	if (!is_power_of_2(extsize))
		return false;

	/* Required to guarantee data block alignment */
	if (mp->m_sb.sb_agblocks % extsize)
		return false;

	/* Requires stripe unit+width be a multiple of extsize */
	if (mp->m_dalign && (mp->m_dalign % extsize))
		return false;

	if (mp->m_swidth && (mp->m_swidth % extsize))
		return false;

	return true;
}


bool xfs_inode_has_atomicwrites(struct xfs_inode *ip)
{
	struct xfs_mount	*mp = ip->i_mount;
	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);

	if (!(ip->i_diflags2 & XFS_DIFLAG2_ATOMICWRITES))
		return false;
	if (!xfs_validate_atomicwrites_extsize(mp, ip->i_extsize))
		return false;
	if (mp->m_sb.sb_blocksize < target->bt_bdev_awu_min)
		return false;
	if (xfs_inode_alloc_unitsize(ip) > target->bt_bdev_awu_max)
		return false;
	return true;
}


static bool xfs_file_open_can_atomicwrite(
	struct inode		*inode,
	struct file		*file)
{
	struct xfs_inode	*ip = XFS_I(inode);

	if (!(file->f_flags & O_DIRECT))
		return false;
	return xfs_inode_has_atomicwrites(ip);
}

Those helpers can be re-used in xfs_inode_validate_atomicwrites() and
xfs_ioctl_setattr_atomicwrites().

Looks good to me.

--D

John