diff mbox series

[08/23] parisc: add pte_unmap() to balance get_ptep()

Message ID 44ebbf90-5fbb-2815-17c7-fcfe3c87d78e@google.com
State New
Headers
Series arch: allow pte_offset_map[_lock]() to fail |

Commit Message

Hugh Dickins May 10, 2023, 4:52 a.m. UTC 
  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 <hughd@google.com>
---
 arch/parisc/kernel/cache.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

Comments

Helge Deller May 13, 2023, 9:35 p.m. UTC | #1 
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 <hughd@google.com>
> ---
>   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
Hugh Dickins May 14, 2023, 6:20 p.m. UTC | #2 
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 <hughd@google.com>
> > ---
> >   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
diff mbox series

Patch

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));