quoted

quoted

-static inline unsigned long dax_folio_share_put(struct folio *folio)
+static inline unsigned long dax_folio_put(struct folio *folio)
   {
-	return --folio->page.share;
+	unsigned long ref;
+	int order, i;
+
+	if (!dax_folio_is_shared(folio))
+		ref = 0;
+	else
+		ref = --folio->share;
+

out of interest, what synchronizes access to folio->share?

Actually that's an excellent question as I hadn't looked too closely at this
given I wasn't changing the overall flow with regards to synchronization, merely
representation of the "shared" state. So I don't have a good answer for you off
the top of my head - Dan maybe you can shed some light here?

Not that I understand what that dax-shared thing is or does, but the 
non-atomic update on a folio_put path looked "surprising".

quoted

quoted

diff --git a/include/linux/dax.h b/include/linux/dax.h
index 2333c30..dcc9fcd 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h

@@ -209,7 +209,7 @@ int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,

[...]

quoted

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d189826..1a0d6a8 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c

@@ -2225,7 +2225,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
   						tlb->fullmm);
   	arch_check_zapped_pmd(vma, orig_pmd);
   	tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
-	if (vma_is_special_huge(vma)) {
+	if (!vma_is_dax(vma) && vma_is_special_huge(vma)) {

I wonder if we actually want to remove the vma_is_dax() check from
vma_is_special_huge(), and instead add it to the remaining callers of
vma_is_special_huge() that still need it -- if any need it.

Did we sanity-check which callers of vma_is_special_huge() still need it? Is
there still reason to have that DAX check in vma_is_special_huge()?

If by "we" you mean "me" then yes :) There are still a few callers of it, mainly
for page splitting.

Heh, "you or any of the reviewers" :)

So IIUC, the existing users still need the DAX check I assume (until 
that part is cleaned up, below).

quoted

But vma_is_special_huge() is rather confusing from me ... the whole
vma_is_special_huge() thing should probably be removed. That's a cleanup for
another day, though.

But after double checking I have come to the same conclusion as you - it should
be removed. I will add that to my ever growing clean-up series that can go on
top of this one.

Nice!

-- 
Cheers,

David / dhildenb