Re: [PATCH 2/2] fsdax,xfs: port unshare to fsdax

Darrick J. Wong
2022-11-30T03:28:53Z

On Thu, Nov 24, 2022 at 02:54:54PM +0000, Shiyang Ruan wrote:
> Implement unshare in fsdax mode: copy data from srcmap to iomap.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>

Heh, I had a version nearly like this in my tree. Makes reviewing
easier:
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
> fs/dax.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
> fs/xfs/xfs_reflink.c | 8 +++++--
> include/linux/dax.h | 2 ++
> 3 files changed, 60 insertions(+), 2 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 5ea7c0926b7f..3d0bf68ab6b0 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1235,6 +1235,58 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
> }
> #endif /* CONFIG_FS_DAX_PMD */
>
> +static s64 dax_unshare_iter(struct iomap_iter *iter)
> +{
> + struct iomap *iomap = &iter->iomap;
> + const struct iomap *srcmap = iomap_iter_srcmap(iter);
> + loff_t pos = iter->pos;
> + loff_t length = iomap_length(iter);
> + int id = 0;
> + s64 ret = 0;
> + void *daddr = NULL, *saddr = NULL;
> +
> + /* don't bother with blocks that are not shared to start with */
> + if (!(iomap->flags & IOMAP_F_SHARED))
> + return length;
> + /* don't bother with holes or unwritten extents */
> + if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
> + return length;
> +
> + id = dax_read_lock();
> + ret = dax_iomap_direct_access(iomap, pos, length, &daddr, NULL);
> + if (ret < 0)
> + goto out_unlock;
> +
> + ret = dax_iomap_direct_access(srcmap, pos, length, &saddr, NULL);
> + if (ret < 0)
> + goto out_unlock;
> +
> + ret = copy_mc_to_kernel(daddr, saddr, length);
> + if (ret)
> + ret = -EIO;
> +
> +out_unlock:
> + dax_read_unlock(id);
> + return ret;
> +}
> +
> +int dax_file_unshare(struct inode *inode, loff_t pos, loff_t len,
> + const struct iomap_ops *ops)
> +{
> + struct iomap_iter iter = {
> + .inode = inode,
> + .pos = pos,
> + .len = len,
> + .flags = IOMAP_WRITE | IOMAP_UNSHARE | IOMAP_DAX,
> + };
> + int ret;
> +
> + while ((ret = iomap_iter(&iter, ops)) > 0)
> + iter.processed = dax_unshare_iter(&iter);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(dax_file_unshare);
> +
> static int dax_memzero(struct iomap_iter *iter, loff_t pos, size_t size)
> {
> const struct iomap *iomap = &iter->iomap;
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 93bdd25680bc..fe46bce8cae6 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1693,8 +1693,12 @@ xfs_reflink_unshare(
>
> inode_dio_wait(inode);
>
> - error = iomap_file_unshare(inode, offset, len,
> - &xfs_buffered_write_iomap_ops);
> + if (IS_DAX(inode))
> + error = dax_file_unshare(inode, offset, len,
> + &xfs_dax_write_iomap_ops);
> + else
> + error = iomap_file_unshare(inode, offset, len,
> + &xfs_buffered_write_iomap_ops);
> if (error)
> goto out;
>
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index ba985333e26b..2b5ecb591059 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -205,6 +205,8 @@ static inline void dax_unlock_mapping_entry(struct address_space *mapping,
> }
> #endif
>
> +int dax_file_unshare(struct inode *inode, loff_t pos, loff_t len,
> + const struct iomap_ops *ops);
> int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
> const struct iomap_ops *ops);
> int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
> --
> 2.38.1
>