Re: [PATCH 08/23] parisc: add pte_unmap() to balance get_ptep()
On Sat, 13 May 2023, Helge Deller wrote:
> Hi Hugh,
>
> On 5/10/23 06:52, Hugh Dickins wrote:
> > To keep balance in future, remember to pte_unmap() after a successful
> > get_ptep(). And (we might as well) pretend that flush_cache_pages()
> > really needed a map there, to read the pfn before "unmapping".
> >
> > Signed-off-by: Hugh Dickins
> > ---
> > arch/parisc/kernel/cache.c | 26 +-
> > 1 file changed, 21 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
> > index 1d3b8bc8a623..b0c969b3a300 100644
> > --- a/arch/parisc/kernel/cache.c
> > +++ b/arch/parisc/kernel/cache.c
> > @@ -425,10 +425,15 @@ void flush_dcache_page(struct page *page)
> > offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
> > addr = mpnt->vm_start + offset;
> > if (parisc_requires_coherency()) {
> > + bool needs_flush = false;
> > pte_t *ptep;
> >
> > ptep = get_ptep(mpnt->vm_mm, addr);
> > - if (ptep && pte_needs_flush(*ptep))
> > + if (ptep) {
> > + needs_flush = pte_needs_flush(*ptep);
> > + pte_unmap(ptep);
> > + }
> > + if (needs_flush)
> > flush_user_cache_page(mpnt, addr);
> > } else {
> > /*
> > @@ -560,14 +565,20 @@ EXPORT_SYMBOL(flush_kernel_dcache_page_addr);
> > static void flush_cache_page_if_present(struct vm_area_struct *vma,
> > unsigned long vmaddr, unsigned long pfn)
> > {
> > - pte_t *ptep = get_ptep(vma->vm_mm, vmaddr);
> > + bool needs_flush = false;
> > + pte_t *ptep;
> >
> >/*
> > * The pte check is racy and sometimes the flush will trigger
> > * a non-access TLB miss. Hopefully, the page has already been
> > * flushed.
> > */
> > - if (ptep && pte_needs_flush(*ptep))
> > + ptep = get_ptep(vma->vm_mm, vmaddr);
> > + if (ptep) {
> > + needs_flush = pte_needs_flush(*ptep))
>
> ^
> One ")" too much and lacks a trailing ";"
> Should be:
> needs_flush = pte_needs_flush(*ptep);
>
> With that fixed the kernel compiles and boots sucessfully on parisc.
Urgh! Indeed, thanks a lot Helge: I'll fold that in.
Hugh
Re: [PATCH 08/23] parisc: add pte_unmap() to balance get_ptep()
Hi Hugh,
On 5/10/23 06:52, Hugh Dickins wrote:
To keep balance in future, remember to pte_unmap() after a successful
get_ptep(). And (we might as well) pretend that flush_cache_pages()
really needed a map there, to read the pfn before "unmapping".
Signed-off-by: Hugh Dickins
---
arch/parisc/kernel/cache.c | 26 +-
1 file changed, 21 insertions(+), 5 deletions(-)
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 1d3b8bc8a623..b0c969b3a300 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -425,10 +425,15 @@ void flush_dcache_page(struct page *page)
offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
addr = mpnt->vm_start + offset;
if (parisc_requires_coherency()) {
+ bool needs_flush = false;
pte_t *ptep;
ptep = get_ptep(mpnt->vm_mm, addr);
- if (ptep && pte_needs_flush(*ptep))
+ if (ptep) {
+ needs_flush = pte_needs_flush(*ptep);
+ pte_unmap(ptep);
+ }
+ if (needs_flush)
flush_user_cache_page(mpnt, addr);
} else {
/*
@@ -560,14 +565,20 @@ EXPORT_SYMBOL(flush_kernel_dcache_page_addr);
static void flush_cache_page_if_present(struct vm_area_struct *vma,
unsigned long vmaddr, unsigned long pfn)
{
- pte_t *ptep = get_ptep(vma->vm_mm, vmaddr);
+ bool needs_flush = false;
+ pte_t *ptep;
/*
* The pte check is racy and sometimes the flush will trigger
* a non-access TLB miss. Hopefully, the page has already been
* flushed.
*/
- if (ptep && pte_needs_flush(*ptep))
+ ptep = get_ptep(vma->vm_mm, vmaddr);
+ if (ptep) {
+ needs_flush = pte_needs_flush(*ptep))
^
One ")" too much and lacks a trailing ";"
Should be:
needs_flush = pte_needs_flush(*ptep);
With that fixed the kernel compiles and boots sucessfully on parisc.
Helge
[PATCH 08/23] parisc: add pte_unmap() to balance get_ptep()
To keep balance in future, remember to pte_unmap() after a successful
get_ptep(). And (we might as well) pretend that flush_cache_pages()
really needed a map there, to read the pfn before "unmapping".
Signed-off-by: Hugh Dickins
---
arch/parisc/kernel/cache.c | 26 +-
1 file changed, 21 insertions(+), 5 deletions(-)
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 1d3b8bc8a623..b0c969b3a300 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -425,10 +425,15 @@ void flush_dcache_page(struct page *page)
offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
addr = mpnt->vm_start + offset;
if (parisc_requires_coherency()) {
+ bool needs_flush = false;
pte_t *ptep;
ptep = get_ptep(mpnt->vm_mm, addr);
- if (ptep && pte_needs_flush(*ptep))
+ if (ptep) {
+ needs_flush = pte_needs_flush(*ptep);
+ pte_unmap(ptep);
+ }
+ if (needs_flush)
flush_user_cache_page(mpnt, addr);
} else {
/*
@@ -560,14 +565,20 @@ EXPORT_SYMBOL(flush_kernel_dcache_page_addr);
static void flush_cache_page_if_present(struct vm_area_struct *vma,
unsigned long vmaddr, unsigned long pfn)
{
- pte_t *ptep = get_ptep(vma->vm_mm, vmaddr);
+ bool needs_flush = false;
+ pte_t *ptep;
/*
* The pte check is racy and sometimes the flush will trigger
* a non-access TLB miss. Hopefully, the page has already been
* flushed.
*/
- if (ptep && pte_needs_flush(*ptep))
+ ptep = get_ptep(vma->vm_mm, vmaddr);
+ if (ptep) {
+ needs_flush = pte_needs_flush(*ptep))
+ pte_unmap(ptep);
+ }
+ if (needs_flush)
flush_cache_page(vma, vmaddr, pfn);
}
@@ -634,17 +645,22 @@ static void flush_cache_pages(struct vm_area_struct *vma,
unsigned long start, u
pte_t *ptep;
for (addr = start; addr < end; addr += PAGE_SIZE) {
+ bool needs_flush = false;
/*
* The vma can contain pages that aren't present. Although
* the pte search is expensive, we need the pte to find the
* page pfn and to check whether the page should be flushed.
*/
ptep = get_ptep(vma->vm_mm, addr);
- if (ptep && pte_needs_flush(*ptep)) {
+ if (ptep) {
+ needs_flush = pte_needs_flush(*ptep);
+ pfn = pte_pfn(*ptep);
+ pte_unmap(ptep);
+ }
+ if (needs_flush) {
if (parisc_requires_coherency()) {
flush_user_cache_page(vma, addr);
} else {
- pfn = pte_pfn(*ptep);
if (WARN_ON(!pfn_valid(pfn)))
return;
__flush_cache_page(vma, addr, PFN_PHYS(pfn));
--
2.35.3
