On Thu, Apr 08, 2021 at 08:04:32PM +0800, Shiyang Ruan wrote:
> Add xfs_break_two_dax_layouts() to break layout for tow dax files. Then
> call compare range function only when files are both DAX or not.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> ---
> fs/xfs/xfs_file.c | 20 ++++++++++++++++++++
> fs/xfs/xfs_inode.c | 8 +++++++-
> fs/xfs/xfs_inode.h | 1 +
> fs/xfs/xfs_reflink.c | 5 +++--
> 4 files changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 5795d5d6f869..1fd457167c12 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -842,6 +842,26 @@ xfs_break_dax_layouts(
> 0, 0, xfs_wait_dax_page(inode));
> }
>
> +int
> +xfs_break_two_dax_layouts(
> + struct inode *src,
> + struct inode *dest)
> +{
> + int error;
> + bool retry = false;
> +
> +retry:
> + error = xfs_break_dax_layouts(src, &retry);
> + if (error || retry)
> + goto retry;
> +
> + error = xfs_break_dax_layouts(dest, &retry);
> + if (error || retry)
> + goto retry;
> +
> + return error;
> +}
> +
> int
> xfs_break_layouts(
> struct inode *inode,
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index f93370bd7b1e..c01786917eef 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3713,8 +3713,10 @@ xfs_ilock2_io_mmap(
> struct xfs_inode *ip2)
> {
> int ret;
> + struct inode *inode1 = VFS_I(ip1);
> + struct inode *inode2 = VFS_I(ip2);
>
> - ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
> + ret = xfs_iolock_two_inodes_and_break_layout(inode1, inode2);
> if (ret)
> return ret;
> if (ip1 == ip2)
> @@ -3722,6 +3724,10 @@ xfs_ilock2_io_mmap(
> else
> xfs_lock_two_inodes(ip1, XFS_MMAPLOCK_EXCL,
> ip2, XFS_MMAPLOCK_EXCL);
> +
> + if (IS_DAX(inode1) && IS_DAX(inode2))
> + ret = xfs_break_two_dax_layouts(inode1, inode2);
This is wrong on many levels.
The first problem is that xfs_break_two_dax_layouts calls
xfs_break_dax_layouts twice even if inode1 == inode2, which is
unnecessary.
The second problem is that xfs_break_dax_layouts can cycle the MMAPLOCK
on the inode that it's processing. Since there are two inodes in play
here, you must be /very/ careful about maintaining correct locking order,
which for the MMAPLOCK is increasing order of xfs_inode.i_ino. If you
drop the MMAPLOCK for the lower-numbered inode for any reason, you have
to drop both MMAPLOCKs and try again.
In other words, you have to replace all that nice MMAPLOCK code with a
new xfs_mmaplock_two_inodes_and_break_dax_layouts function that is
structured similarly to what xfs_iolock_two_inodes_and_break_layout
does for the IOLOCK and PNFS layouts.
> +
> return 0;
> }
>
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index 88ee4c3930ae..5ef21924dddc 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -435,6 +435,7 @@ enum xfs_prealloc_flags {
>
> int xfs_update_prealloc_flags(struct xfs_inode *ip,
> enum xfs_prealloc_flags flags);
> +int xfs_break_two_dax_layouts(struct inode *inode1, struct inode *inode2);
> int xfs_break_layouts(struct inode *inode, uint *iolock,
> enum layout_break_reason reason);
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index a4cd6e8a7aa0..4426bcc8a985 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -29,6 +29,7 @@
> #include "xfs_iomap.h"
> #include "xfs_sb.h"
> #include "xfs_ag_resv.h"
> +#include <linux/dax.h>
Why is this necessary?
--D
>
> /*
> * Copy on Write of Shared Blocks
> @@ -1324,8 +1325,8 @@ xfs_reflink_remap_prep(
> if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
> goto out_unlock;
>
> - /* Don't share DAX file data for now. */
> - if (IS_DAX(inode_in) || IS_DAX(inode_out))
> + /* Don't share DAX file data with non-DAX file. */
> + if (IS_DAX(inode_in) != IS_DAX(inode_out))
> goto out_unlock;
>
> if (!IS_DAX(inode_in))
> --
> 2.31.0
>
>
>
