On Fri, Sep 02, 2022 at 05:28:47PM +0100, Catalin Marinas wrote:
> On Fri, Sep 02, 2022 at 03:47:33PM +0100, Steven Price wrote:
> > On 10/08/2022 20:30, Peter Collingbourne wrote:
> > > diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c
> > > index a78c1db23c68..cd5ad0936e16 100644
> > > --- a/arch/arm64/mm/mteswap.c
> > > +++ b/arch/arm64/mm/mteswap.c
> > > @@ -53,6 +53,9 @@ bool mte_restore_tags(swp_entry_t entry, struct page *page)
> > > if (!tags)
> > > return false;
> > >
> > > + /* racing tag restoring? */
> > > + if (!try_page_mte_tagging(page))
> > > + return false;
> > > mte_restore_page_tags(page_address(page), tags);
> >
> > I feel like adding a "set_page_mte_tagged(page);" in here would avoid
> > the need for the comments about mte_restore_tags() taking the lock.
>
> Good point. I think I blindly followed the set_bit() places but it makes
> sense to move the bit setting to mte_restore_tags().
Something like this (and I need to do some more testing):
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index b956899467f0..be6560e1ff2b 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -25,7 +25,7 @@ unsigned long mte_copy_tags_to_user(void __user *to, void *from,
unsigned long n);
int mte_save_tags(struct page *page);
void mte_save_page_tags(const void *page_addr, void *tag_storage);
-bool mte_restore_tags(swp_entry_t entry, struct page *page);
+void mte_restore_tags(swp_entry_t entry, struct page *page);
void mte_restore_page_tags(void *page_addr, const void *tag_storage);
void mte_invalidate_tags(int type, pgoff_t offset);
void mte_invalidate_tags_area(int type);
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e6b82ad1e9e6..7d91379382fd 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1049,9 +1049,8 @@ static inline void arch_swap_invalidate_area(int type)
#define __HAVE_ARCH_SWAP_RESTORE
static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
{
- /* mte_restore_tags() takes the PG_mte_lock */
- if (system_supports_mte() && mte_restore_tags(entry, &folio->page))
- set_page_mte_tagged(&folio->page);
+ if (system_supports_mte())
+ mte_restore_tags(entry, &folio->page);
}
#endif /* CONFIG_ARM64_MTE */
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 634e089b5933..54ab6c4741db 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -41,11 +41,8 @@ static void mte_sync_page_tags(struct page *page, pte_t old_pte,
if (check_swap && is_swap_pte(old_pte)) {
swp_entry_t entry = pte_to_swp_entry(old_pte);
- /* mte_restore_tags() takes the PG_mte_lock */
- if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) {
- set_page_mte_tagged(page);
- return;
- }
+ if (!non_swap_entry(entry))
+ mte_restore_tags(entry, page);
}
if (!pte_is_tagged)
diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c
index cd5ad0936e16..cd508ba80ab1 100644
--- a/arch/arm64/mm/mteswap.c
+++ b/arch/arm64/mm/mteswap.c
@@ -46,19 +46,17 @@ int mte_save_tags(struct page *page)
return 0;
}
-bool mte_restore_tags(swp_entry_t entry, struct page *page)
+void mte_restore_tags(swp_entry_t entry, struct page *page)
{
void *tags = xa_load(&mte_pages, entry.val);
if (!tags)
- return false;
+ return;
- /* racing tag restoring? */
- if (!try_page_mte_tagging(page))
- return false;
- mte_restore_page_tags(page_address(page), tags);
-
- return true;
+ if (try_page_mte_tagging(page)) {
+ mte_restore_page_tags(page_address(page), tags);
+ set_page_mte_tagged(page);
+ }
}
void mte_invalidate_tags(int type, pgoff_t offset)
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