On 2/14/16 11:22 PM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> If the block size of a filesystem is not at least PAGE_SIZEd, then
> at this point in time DAX cannot be used due to the fact we can't
> guarantee extents are page sized or aligned without further work.
> Hence disallow setting the DAX flag on an inode if the block size is
> too small. Also, be defensive and check the block size when reading
> an inode in off disk.
>
> In future, we want to allow DAX to work on any filesystem, so this
> is temporary while we sort of the correct conbination of extent size
> hints and allocation alignment configurations needed to guarantee
> page sized and aligned extent allocation for DAX enabled files.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> fs/xfs/xfs_ioctl.c | 12 ++++++++----
> fs/xfs/xfs_iops.c | 1 +
> 2 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index a870d16..8e9cd3c 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1080,11 +1080,15 @@ xfs_ioctl_setattr_dax_invalidate(
>
> /*
> * It is only valid to set the DAX flag on regular files and
> - * directories. On directories it serves as an inherit hint.
> + * directories on filesystems where the block size is at least the page
^^^^^^^^
> + * size. On directories it serves as an inherit hint.
> */
> - if ((fa->fsx_xflags & FS_XFLAG_DAX) &&
> - !(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
> - return -EINVAL;
> + if (fa->fsx_xflags & FS_XFLAG_DAX) {
> + if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
> + return -EINVAL;
> + if (ip->i_mount->m_sb.sb_blocksize != PAGE_SIZE)
^^
So which is it, at least PAGE_SIZE or == PAGE_SIZE?
> + 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))
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 9c984a0..fb7dc61 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -1186,6 +1186,7 @@ xfs_diflags_to_iflags(
> if (flags & XFS_DIFLAG_NOATIME)
> inode->i_flags |= S_NOATIME;
> if (S_ISREG(inode->i_mode) &&
> + ip->i_mount->m_sb.sb_blocksize == PAGE_SIZE &&
> (ip->i_mount->m_flags & XFS_MOUNT_DAX ||
> ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
> inode->i_flags |= S_DAX;
Is it possible to get mounted with XFS_MOUNT_DAX if blocksize != PAGE_SIZE?
If so, should it be? This seems like a strange place to catch this mismatch.
-Eric
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