Re: [PATCH V11 11/11] fs/xfs: Update xfs_ioctl_setattr_dax_invalidate()

Darrick J. Wong
2020-06-02T17:24:17Z

On Tue, Apr 28, 2020 at 01:11:38PM -0700, Darrick J. Wong wrote:
> On Mon, Apr 27, 2020 at 05:21:42PM -0700, ira.weiny@intel.com wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> >
> > Because of the separation of FS_XFLAG_DAX from S_DAX and the delayed
> > setting of S_DAX, data invalidation no longer needs to happen when
> > FS_XFLAG_DAX is changed.
> >
> > Change xfs_ioctl_setattr_dax_invalidate() to be
> > xfs_ioctl_dax_check_set_cache() and alter the code to reflect the new
> > functionality.
> >
> > Furthermore, we no longer need the locking so we remove the join_flags
> > logic.
> >
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>
> Looks ok,
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
>
> --D
>
> >
> > ---
> > Changes from V10:
> > adjust for renamed d_mark_dontcache() function
> >
> > Changes from V9:
> > Change name of function to xfs_ioctl_setattr_prepare_dax()
> >
> > Changes from V8:
> > Change name of function to xfs_ioctl_dax_check_set_cache()
> > Update commit message
> > Fix bit manipulations
> >
> > Changes from V7:
> > Use new flag_inode_dontcache()
> > Skip don't cache if mount over ride is active.
> >
> > Changes from v6:
> > Fix completely broken implementation and update commit message.
> > Use the new VFS layer I_DONTCACHE to facilitate inode eviction
> > and S_DAX changing on drop_caches
> >
> > Changes from v5:
> > New patch
> > ---
> > fs/xfs/xfs_ioctl.c | 108 +++++++++------------------------------------
> > 1 file changed, 20 insertions(+), 88 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index 104495ac187c..ff474f2c9acf 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -1245,64 +1245,26 @@ xfs_ioctl_setattr_xflags(
> > return 0;
> > }
> >
> > -/*
> > - * If we are changing DAX flags, we have to ensure the file is clean and any
> > - * cached objects in the address space are invalidated and removed. This
> > - * requires us to lock out other IO and page faults similar to a truncate
> > - * operation. The locks need to be held until the transaction has been committed
> > - * so that the cache invalidation is atomic with respect to the DAX flag
> > - * manipulation.
> > - */
> > -static int
> > -xfs_ioctl_setattr_dax_invalidate(
> > +static void
> > +xfs_ioctl_setattr_prepare_dax(
> > struct xfs_inode *ip,
> > - struct fsxattr *fa,
> > - int *join_flags)
> > + struct fsxattr *fa)
> > {
> > - struct inode *inode = VFS_I(ip);
> > - struct super_block *sb = inode->i_sb;
> > - int error;
> > -
> > - *join_flags = 0;
> > -
> > - /*
> > - * It is only valid to set the DAX flag on regular files and
> > - * directories on filesystems where the block size is equal to the page
> > - * size. On directories it serves as an inherited hint so we don't
> > - * have to check the device for dax support or flush pagecache.
> > - */
> > - if (fa->fsx_xflags & FS_XFLAG_DAX) {
> > - struct xfs_buftarg *target = xfs_inode_buftarg(ip);
> > -
> > - if (!bdev_dax_supported(target->bt_bdev, sb->s_blocksize))
> > - return -EINVAL;
> > - }
> > -
> > - /* If the DAX state is not changing, we have nothing to do here. */
> > - if ((fa->fsx_xflags & FS_XFLAG_DAX) && IS_DAX(inode))
> > - return 0;
> > - if (!(fa->fsx_xflags & FS_XFLAG_DAX) && !IS_DAX(inode))
> > - return 0;
> > + struct xfs_mount *mp = ip->i_mount;
> > + struct inode *inode = VFS_I(ip);
> >
> > if (S_ISDIR(inode->i_mode))
> > - return 0;
> > -
> > - /* lock, flush and invalidate mapping in preparation for flag change */
> > - xfs_ilock(ip, XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL);
> > - error = filemap_write_and_wait(inode->i_mapping);
> > - if (error)
> > - goto out_unlock;
> > - error = invalidate_inode_pages2(inode->i_mapping);
> > - if (error)
> > - goto out_unlock;
> > -
> > - *join_flags = XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL;
> > - return 0;
> > + return;
> >
> > -out_unlock:
> > - xfs_iunlock(ip, XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL);
> > - return error;
> > + if ((mp->m_flags & XFS_MOUNT_DAX_ALWAYS) ||
> > + (mp->m_flags & XFS_MOUNT_DAX_NEVER))
> > + return;
> >
> > + if (((fa->fsx_xflags & FS_XFLAG_DAX) &&
> > + !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)) ||
> > + (!(fa->fsx_xflags & FS_XFLAG_DAX) &&
> > + (ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)))
> > + d_mark_dontcache(inode);

Now that I think about this further, are we /really/ sure that we want
to let unprivileged userspace cause inode evictions?

--D

> > }
> >
> > /*
> > @@ -1310,17 +1272,10 @@ xfs_ioctl_setattr_dax_invalidate(
> > * have permission to do so. On success, return a clean transaction and the
> > * inode locked exclusively ready for further operation specific checks. On
> > * failure, return an error without modifying or locking the inode.
> > - *
> > - * The inode might already be IO locked on call. If this is the case, it is
> > - * indicated in @join_flags and we take full responsibility for ensuring they
> > - * are unlocked from now on. Hence if we have an error here, we still have to
> > - * unlock them. Otherwise, once they are joined to the transaction, they will
> > - * be unlocked on commit/cancel.
> > */
> > static struct xfs_trans *
> > xfs_ioctl_setattr_get_trans(
> > - struct xfs_inode *ip,
> > - int join_flags)
> > + struct xfs_inode *ip)
> > {
> > struct xfs_mount *mp = ip->i_mount;
> > struct xfs_trans *tp;
> > @@ -1337,8 +1292,7 @@ xfs_ioctl_setattr_get_trans(
> > goto out_unlock;
> >
> > xfs_ilock(ip, XFS_ILOCK_EXCL);
> > - xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL | join_flags);
> > - join_flags = 0;
> > + xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
> >
> > /*
> > * CAP_FOWNER overrides the following restrictions:
> > @@ -1359,8 +1313,6 @@ xfs_ioctl_setattr_get_trans(
> > out_cancel:
> > xfs_trans_cancel(tp);
> > out_unlock:
> > - if (join_flags)
> > - xfs_iunlock(ip, join_flags);
> > return ERR_PTR(error);
> > }
> >
> > @@ -1486,7 +1438,6 @@ xfs_ioctl_setattr(
> > struct xfs_dquot *pdqp = NULL;
> > struct xfs_dquot *olddquot = NULL;
> > int code;
> > - int join_flags = 0;
> >
> > trace_xfs_ioctl_setattr(ip);
> >
> > @@ -1510,18 +1461,9 @@ xfs_ioctl_setattr(
> > return code;
> > }
> >
> > - /*
> > - * Changing DAX config may require inode locking for mapping
> > - * invalidation. These need to be held all the way to transaction commit
> > - * or cancel time, so need to be passed through to
> > - * xfs_ioctl_setattr_get_trans() so it can apply them to the join call
> > - * appropriately.
> > - */
> > - code = xfs_ioctl_setattr_dax_invalidate(ip, fa, &join_flags);
> > - if (code)
> > - goto error_free_dquots;
> > + xfs_ioctl_setattr_prepare_dax(ip, fa);
> >
> > - tp = xfs_ioctl_setattr_get_trans(ip, join_flags);
> > + tp = xfs_ioctl_setattr_get_trans(ip);
> > if (IS_ERR(tp)) {
> > code = PTR_ERR(tp);
> > goto error_free_dquots;
> > @@ -1651,7 +1593,6 @@ xfs_ioc_setxflags(
> > struct fsxattr fa;
> > struct fsxattr old_fa;
> > unsigned int flags;
> > - int join_flags = 0;
> > int error;
> >
> > if (copy_from_user(&flags, arg, sizeof(flags)))
> > @@ -1668,18 +1609,9 @@ xfs_ioc_setxflags(
> > if (error)
> > return error;
> >
> > - /*
> > - * Changing DAX config may require inode locking for mapping
> > - * invalidation. These need to be held all the way to transaction commit
> > - * or cancel time, so need to be passed through to
> > - * xfs_ioctl_setattr_get_trans() so it can apply them to the join call
> > - * appropriately.
> > - */
> > - error = xfs_ioctl_setattr_dax_invalidate(ip, &fa, &join_flags);
> > - if (error)
> > - goto out_drop_write;
> > + xfs_ioctl_setattr_prepare_dax(ip, &fa);
> >
> > - tp = xfs_ioctl_setattr_get_trans(ip, join_flags);
> > + tp = xfs_ioctl_setattr_get_trans(ip);
> > if (IS_ERR(tp)) {
> > error = PTR_ERR(tp);
> > goto out_drop_write;
> > --
> > 2.25.1
> >