On Thu, Sep 02, 2021 at 09:43:08AM +0200, Christoph Hellwig wrote:
> On Sun, Aug 29, 2021 at 08:25:16PM +0800, Shiyang Ruan wrote:
> > In fsdax mode, WRITE and ZERO on a shared extent need CoW performed.
> > After that, new allocated extents needs to be remapped to the file. Add
> > an implementation of ->iomap_end() for dax write ops to do the remapping
> > work.
>
> Please split the new dax infrastructure from the XFS changes.
>
> > static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> > - int *iomap_errp, const struct iomap_ops *ops)
> > + int *iomap_errp, const struct iomap_ops *ops)
> > {
> > struct address_space *mapping = vmf->vma->vm_file->f_mapping;
> > XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
> > @@ -1631,7 +1664,7 @@ static bool dax_fault_check_fallback(struct vm_fault *vmf, struct xa_state *xas,
> > }
> >
> > static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
> > - const struct iomap_ops *ops)
> > + const struct iomap_ops *ops)
>
> These looks like unrelated whitespace changes.
>
> > -static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
> > +loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
> > {
> > const struct iomap *iomap = &iter->iomap;
> > const struct iomap *srcmap = iomap_iter_srcmap(iter);
> > @@ -918,6 +918,7 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
> >
> > return written;
> > }
> > +EXPORT_SYMBOL_GPL(iomap_zero_iter);
>
> I don't see why this would have to be exported.
>
> > + unsigned flags,
> > + struct iomap *iomap)
> > +{
> > + int error = 0;
> > + struct xfs_inode *ip = XFS_I(inode);
> > + bool cow = xfs_is_cow_inode(ip);
>
> The cow variable is only used once, so I think we can drop it.
>
> > + const struct iomap_iter *iter =
> > + container_of(iomap, typeof(*iter), iomap);
>
> Please comment this as it is a little unusual.
>
> > +
> > + if (cow) {
> > + if (iter->processed <= 0)
> > + xfs_reflink_cancel_cow_range(ip, pos, length, true);
> > + else
> > + error = xfs_reflink_end_cow(ip, pos, iter->processed);
> > + }
> > + return error ?: iter->processed;
>
> The ->iomap_end convention is to return 0 or a negative error code.
> Also i'd much prefer to just spell this out in a normal sequential way:
>
> if (!xfs_is_cow_inode(ip))
> return 0;
>
> if (iter->processed <= 0) {
> xfs_reflink_cancel_cow_range(ip, pos, length, true);
> return 0;
> }
>
> return xfs_reflink_end_cow(ip, pos, iter->processed);
Seeing as written either contains iter->processed if it's positive, or
zero if nothing got written or there were errors, I wonder why this
isn't just:
if (!xfs_is_cow_inode(ip));
return 0;
if (!written) {
xfs_reflink_cancel_cow_range(ip, pos, length, true);
return 0;
}
return xfs_reflink_end_cow(ip, pos, written);
? (He says while cleaning up trying to leave for vacation, pardon me
if this comment is totally boneheaded...)
--D
> > +static inline int
> > +xfs_iomap_zero_range(
> > + struct xfs_inode *ip,
> > + loff_t pos,
> > + loff_t len,
> > + bool *did_zero)
> > +{
> > + struct inode *inode = VFS_I(ip);
> > +
> > + return IS_DAX(inode)
> > + ? dax_iomap_zero_range(inode, pos, len, did_zero,
> > + &xfs_dax_write_iomap_ops)
> > + : iomap_zero_range(inode, pos, len, did_zero,
> > + &xfs_buffered_write_iomap_ops);
> > +}
>
> if (IS_DAX(inode))
> return dax_iomap_zero_range(inode, pos, len, did_zero,
> &xfs_dax_write_iomap_ops);
> return iomap_zero_range(inode, pos, len, did_zero,
> &xfs_buffered_write_iomap_ops);
>
> > +static inline int
> > +xfs_iomap_truncate_page(
> > + struct xfs_inode *ip,
> > + loff_t pos,
> > + bool *did_zero)
> > +{
> > + struct inode *inode = VFS_I(ip);
> > +
> > + return IS_DAX(inode)
> > + ? dax_iomap_truncate_page(inode, pos, did_zero,
> > + &xfs_dax_write_iomap_ops)
> > + : iomap_truncate_page(inode, pos, did_zero,
> > + &xfs_buffered_write_iomap_ops);
> > +}
>
> Same here.
